Fuses: What do they do, why do they blow and
what you need to know.

by Boogie on June 15, 2010

in Mesa Boogie Products, Mesa Tones & Tips, Servicing My Mesa Boogie Tube Guitar Amplifier, Troubleshooting

Actual fuses spelling out the word fuse

So your amp doesn’t power up, or it sounded great then cut out and you turned around to see the lights out? Most likely the fuse blew…What’s next?

There’s never a good time for your beloved tube amp to not work but a blown fuse is actually a good thing if you are aware of what it’s trying to tell you. In most cases a blown fuse is signaling a shorted or otherwise failed power or rectifier tube. It’s important to note that Mesa amps are designed in such a way that even the most inexperienced and tube-terrified musician can change a bad tube as easily as you would change a light bulb. That said, let’s first explore the role of the fuse and some basic troubleshooting concepts every tube amp owner and enthusiast should know. With the right perspective, a little knowledge and spare tubes and fuses, most fuse-related Mesa amp problems can be solved by the user in just minutes. And that blown fuse you were cursing earlier might actually start to look a lot more like the hero it really is.

The bottom line and THE most important concept to understand about the fuse in an amplifier is…. (drumroll please):

The fuse is in the amplifier to protect the amplifier’s circuit from tube failure and other extreme voltage issues!

When the fuse blows, its not the fuse that’s actually bad. Obviously a blown fuse will no longer allow the amp to function… and that’s by design. Once failed, a blown fuse obviously needs to be replaced but the aspiring troubleshooter must be aware that something caused the fuse to blow, it didn’t just go by itself. That something is almost always a bad power tube or rectifier tube. All tubes wear (like a lightbulb or guitar strings, except over a longer period) and will inevitably fail. With time the likelihood of failure increases and the same tubes that provide your favorite tones can actually pose a risk to the rest of the amp’s circuitry when they fail. Understanding this concept is crucial when addressing an amp whose fuse has just blown or an amp that doesn’t power up.

Let’s talk about what the fuse is and does. From Wikipedia: In electronics and electrical engineering a fuse (from the Latin “fusus” meaning to melt) is a type of sacrificial overcurrent protection device. Its essential component is a metal wire or strip that melts when too much current flows, which interrupts the circuit in which it is connected.

In the case of tube amplifiers, when a tube shorts or fails it draws excess current. When the failed tube draws current beyond the value of the fuse, the wire in the fuse literally melts and cuts off the electricity to the amp. The amp is effectively shut off before more damage can occur. How do you like your fuse now? ;)

The next important concept to consider when addressing a blown fuse is knowing the three things that most commonly cause a fuse to blow:

1. A bad power tube (arcing or shorting)
2. A bad rectifier tube
3. A major power surge

In the case of the first two, regular tube maintenance and general awareness of your amp and its normal operation can help you avoid many failures. That said, tubes fail when THEY want to so there are a few further important considerations to be aware of before engaging in troubleshooting:

- Rarely does more than one tube fail. It’s not impossible but definitely not the norm. Except in extreme cases or physical breakage, you are generally looking for JUST ONE bad tube. Whole sets of tubes do not fail.
- Preamp tubes will not cause a fuse to blow. (whew… check that off the list!) Preamp tubes are not high voltage like power or rectifier tubes and will not cause a fuse to blow.
- Feeding multiple fuses to an amp is not fixing it. Understanding that fuses don’t just ‘go bad’, occasionally a fuse will fail even when all the tubes are perfectly fine. This is generally rare, BUT… trying more than 2 fuses without addressing your power or rectifier tubes can cause further damage to the amp.

OK… you know that preamp tubes aren’t the cause of a blown fuse and you’re pretty sure it wasn’t a power surge so you’re ready to move on to the next steps. If you’re amp has rectifier tubes, the next step is to determine if the blown fuse was caused by a failed rectifier tube or a power tube. If your amp doesn’t have rectifier tubes, you’re already halfway there and its time to zero in on a bad power tube! Specific tube troubleshooting information can be found here for now and we’ll elaborate on these steps in future posts. But, a few final and equally important fuse concepts remain.

In fact, the following fuse info below may actually be MORE important than what we’ve already discussed, and if the above hasn’t sunk in just yet, make sure you at least understand this:

NEVER install a fuse that is rated higher than the required fuse rating printed on the back of your amp!

Likewise, NEVER install tin foil or other conductive items in place of the properly rated fuse in the fuseholder!

You can generate extreme and costly damage to your amp if fuses are bypassed or installed incorrectly. Using the wrong value fuse can lead to one of two undesirable results: a fuse that is a lower value than required by the amp will likely fail as soon as you lift the power switch to the on position regardless of the actual failures that may have caused the original fuse to blow. On the other hand, using a fuse with a higher rating than the required fuse value is almost like having no fuse at all and can cause devastating and expensive failures to other parts of the amp’s circuit. Bottom line – make sure the fuse you are installing is the right one with no exceptions.

With the basics behind us, let’s take a look at the preparedness side of fuses and tube troubleshooting in general. If you operate a tube amplifier, the golden rule is to always have spare tubes AND FUSES in your gig bag. Especially important – all of your spare fuses should be pre-inspected to be the correct value fuse your amp requires. It’s a very good idea to physically check each fuse yourself before installing them to avoid damage from the fuse being incorrect and better to do it when not under pressure to fix the amp at a gig.

Picture of a 4 amp fuseThe fuse’s rating is printed on the metal end of the fuse with a number followed by an ‘A’.

Slo-Blo vs. Fast-Blo

Another very important characteristic of fuses you’ll commonly see and need to identify is Slo-Blo vs. Fast-Blo. When first powering up an amp, the current draw of tubes and the voltage to the amp spikes as the power switch is lifted. This voltage spike will briefly exceed the value of the fuse and then settle below the fuses rating into a normal operating range. Fast-Blo fuses will nearly always fail on this initial power up surge which is why they are not used in Mesa amplifier circuits. Slow-Blo fuses are designed to handle a temporary surge of current beyond their rating for a short period (10-20 seconds) before ultimately failing making them perfect for withstanding the initial power up surge.

Helpful Hints and Be Prepared

Fuse Can Mounted to the inside of the ampFinally – some handy hints for fuses and spares. If the fuses you purchase are packaged in a slide-lid style container, after inspecting them, consider mounting them inside the cab near the fuseholder as shown in the photo. You may be able to glue the case to the inside of the cab and if not, consider taping a few fuses to the inside of the cab with some heavy duty gaff or duct tape. It’s not a bad idea to write the value of the fuse on the tape or slide case as an additional reminder when the fuse is needed.

Also helpful in a blown fuse situiation is an indication of when the power or rectifier tubes were last changed in the amp.  Make a note of what tubes were changed and when and write this info on a piece of tape or a label-maker and attach somewhere on the amp as the finishing touch to the retube job. If you’ve played the amp loud and a lot since you changed the power tubes (1-2 years – 15 hours a week), when the fuse blows, the age and wear on a set can be a very helpful troubleshooting tool. Especially if the amp didn’t sound quite as brilliant, bright or punchy, having the date of it’s last retube handy provides pieces of the puzzle, helping you get the amp back up to speed when the fuse kindly requests you take a look. ;)

For further detailed info on fuses (if this wasn’t enough already), the Wikipedia link above offers much more than any guitar player should ever need to know and there’s a ton of other info out there to be had if you want to go that far down the rabbit hole. When the fuse on your amp fails, it’s not only saving your amp from damage beyond a bad tube that needs replacing – its often your amp’s way of telling you that its time to take a look at tube maintenance in general to get your amp back up to it’s original glory. Check back shortly for more detailed insights into tube troubleshooting and amplifier maintenance in future upcoming posts here on the blog and go get your spares kits in order.

And, as always, if you have further questions about your amp, blown fuses or troubleshooting, feel free to call the Mesa factory at (707) 778 6565, Monday-Thursday, 9AM-5PM Pacific Standard Time. Ask for a Product Specialist who can walk you through basic troubleshooting techniques to diagnose your amp and get you back up to speed when the fuse in your amp is trying to tell you something and learn about it all along the way.


{ 112 comments… read them below or add one }

Marcus Vinaud December 17, 2014 at 6:16 am

Can I use a 4A 250v FAST BLOW fuse for a few days in my Mark V head? I order a SLOW BLOW fuse, but i’ll take some days to be here, but I really need to use the amp.

Thank you very much! :)

Cheers from Brazil


Boogie Boogie January 5, 2015 at 12:04 pm

Hi Marcus –

It *may* work but maybe not. Fast-Blo fuses sometimes won’t handle the initial ‘inrush’ of current that happens when you first flip the power or standby switches. The Slo-Blo fuse is designed to be able to handle the current starting out a little strong and then settling down to it’s norm. The Fast-Blo fuse could get prematurely blown even though the amp is fine and you can certainly try using a Fast-Blo fuse (of the proper rating – 4A) as it won’t hurt anything.

Hope this helps and the amp is back up and running with the proper fuse!


electrical fuses,fuses,industrial fuses,bussman fuses,obsolete fuses,cooper bussman September 28, 2013 at 7:43 pm

Thanks for your posting. I get my fuses at fusedepot


Rob May 24, 2013 at 11:41 am


i just bought a lonestar special and literally brought it home and plugged it into socket. (240v) i played it on 5w mode on the clean channel for about 10 mins with no problems at all. i swtiched to channel two and again played for about 10 mins and then the amp powered down and would not power back up.

i returned it to the shop and it appears the fuse was blown. changing the fuse allowed the amp to work at 30w but trying to play at 15 or 5w produced no sound at all.

what happened to the amp and is it a simple fix or is it more serious?

Thanks in advance



Boogie Boogie May 24, 2013 at 10:13 pm

Hi Rob –

Sorry to hear of the troubles with your Lone Star Special.

The problem is with the Rectifier Tube 5Y3. If that tube fails, the amp will not operate in the 5W or 15W modes because these modes does not operate without the Rectifier tube while 30W DOES!

If a fuse blows, it nearly always points to a power or rectifier tube. When the fuse blows, it’s trying to tell you there’s a tube that needs to be replaced. Replace the fuse and the failed tube and you should be back up and running in most cases.

If you ever on the gig and the amp goes out on you using 5W or 15W (and you don’t have a spare 5Y3), you can likely finish the gig on 30W once you’ve removed the failed/shorted 5Y3. Just don’t switch the amp to 5W or 15W with no 5Y3 installed.

Hope this helps and let us know what you find out.


(Edited 7/17/14 for accuracy)


Mike August 17, 2014 at 5:54 am

Tien, that is incorrect. The failure of the rectifier tube 5y3 will result in BOTH the 5 and the 15 watt modes to stop operating. Only the 30 watt mode will operate. And please elaborate on what will happen when you switch the amp to 5 watts without a 5y3 installed. I would think that would be OK. If it’s not, this amp needs a warning not to operate 30 watt mode unless rectifier tube is working.


Boogie Boogie August 17, 2014 at 11:56 am

Hi Rob –

You are correct – thanks for the correction here. The 5Y3 failing will affect BOTH the 5W AND 15W modes. The amp will still works in 30 watts (with a failed or removed Rectifier tube) because the 30watt mode exclusively uses the Silicon Diodes for rectification and bypasses the Rectifier tube. Running the amp in 5W or 15W is NOT RECOMMENDED as the amp REQUIRES a working rectifier when set to 5W & 15W. Thanks for the correction – fixed above. ;)


Andi February 28, 2013 at 3:28 am

Dear Mesa Boogie Team,

maybe you got an idea to solve my problem: I’m using the Lonestar Special Head European Version 230V. I prefer the 5W mode in clean channel. Last week the first fuse was blown. This was the supplied fuse coming with my new bought amp 2 years ago. According to the labeling on the amps backside I need a T 1A fuse, however, the Mesa supplied fuse was a 2A which worked fine now for 2 years.

I replaced the fuse with 1.25A as I guessed the 2A is not the correct one. Everything was working fine for about one hour play in 5W mode until the second fuse has blown – together with my rectifier tube. According to the information I got here I replaced now the 5Y3 tube and put another 1.25A into the amp. However, after 5 minutes of playing the next fuse has gone, also my brand new 5YR is not working anymore. Now I’m stuck to the 30W mode again.

So, its clear I need my 5W mode back. Any ideas? And what is the correct fuse for the 230V version as 1A label but 2A fuse supplied fuse is confusing me a lot.

Thanks, Andi


Boogie January 19, 2013 at 10:35 am

Hi while i’m playing my amp half way up suddenly it makes a boom and my guitar sound dosen’t come from the speakers . it’s strange beacuse the amp still on and work normally i shut it down and tried to turn it again and nothing happends it’s blown fuse or what ? Thanks a lot


Boogie Boogie January 24, 2013 at 10:45 pm

Hi Dr. Guitar -

If the fuse on your amp is not failing the problem is likely either preamp tubes – or – something electronic that is not user serviceable.

If preamp tubes, you should watch the following troubleshooting video and read through the comments and begin preamp tube troubleshooting.


If the problem is not solved by changing tubes, the amp should go to a repair station. If you are outside of the USA, please contact your Mesa distributor for a recommendation to an Authorized Repair Station. Here is a link to search for your local Mesa Distributor:


If you have further questions that are not answered by the local distributor or repair station, feel free to email us at info@mesaboogie.com.

Hope this helps.




Donald Cretsinger December 10, 2012 at 11:31 am

I recently purchased a used Triaxis and it has performed flawlessly for about 3 weeks. I turn it on one day and the internal fuse blows (the unit would not power up). So I replaced the internal fuse with the exact same type and rating, apply power to the unit and the fuse has popped again. What could be causing this issue with my Triaxis? My entire rack is running to a Monster Power power conditioner and none of the other units in my rack have had or are having any issues.


Boogie Boogie December 14, 2012 at 10:10 pm

Hi Don –

That’s a strange problem. It’s important to make sure you are using the EXACT same rated fuse but it’s very rare for the Triaxis fuse to blow unless it is seeing a voltage that is much higher than the rating of the fuse.

You might trying plugging the Triaxis into the wall, away from your power conditioner, but otherwise this is probably something that should be looked at by a technician or something you might send to Mesa for a look.

Hope this helps and if you figured it out we’d be curious to see what you found.



Donald October 8, 2013 at 8:32 am

Found out that the power transformer had a short. Called Mesa/Boogie and had one shipped out overnight and everything is good to go!!!!


Mo November 18, 2012 at 4:03 am


Today I did the worst thing to my Mesa Boogie Preamp … I connected it to 220 power instead of 110. It made a sound and shut and I switched it off and removed the plug immediately! What is the damage you think? I hope it has a safe fuse that will eliminate the damage from reaching anywhere else within the circuit!

Please let me know and your help is always appreciated.

Best regards



Boogie Boogie December 5, 2012 at 3:07 pm

Hi Mo –

Sorry to hear this. Definitely not ideal although sometimes damage can be minimal.

Inside the amp is a component called a Varistor which is inline with the AC to the transformer. This component is designed to fail in the event of a power surge which a 117V amp being plugged into a 220-240V supply certainly qualifies. No doubt this component is failed in your amp and will need to be replaced. However, this component may not have failed in time, along with the fuse itself, and damage to your power transformer is a distinct possibility.

You should take the amp to a Mesa authorized technician to have it looked at as it doesn’t take long for twice the wall voltage to do damage to the amp.

Here’s a link to Mesa distributors you can contact to find the nearest authorized Mesa repair facility to have your amp looked at:


Hope this helps and you get your amp back up and running ASAP.




derick October 14, 2012 at 5:58 am

Hi, please when i on my guitar combo i play for about just a minute and then the sound cuts while the combo is still on. I bought a new cord but it never solved the problem.each time i turn it on off and then on i play for close to a minute and then sound cuts with the combo stil on.what could be the the possible problem?


Boogie Boogie October 16, 2012 at 7:04 pm

Hi Derick –

You are most likely facing tube troubleshooting. The best way to learn and the first place to go is to watch this:


More likely to be preamp tubes than Power or Rectifier tubes. Preamp tubes can fail and cause for no output but the amp still stays powered up.

Follow the instructions in the Tube Troubleshooting video and let us know what you find out.

Hope this helps.



Boogie Boogie September 28, 2012 at 9:51 pm

See the reply above to the same questions. Easy fix by changing the 5Y3 rectifier tube.


Tim September 28, 2012 at 9:49 am

The wattage selecter on my single 12″ Mesa Lone Star Special doesn’t work on either channel in the 5 or 15 watt position. It works in the 30 watt position. The ammp is 4 years old and the Power tubes are new.



Boogie Boogie September 28, 2012 at 12:46 pm

Hi Tim –

Bad 5Y3 rectifier tube. In use in 5 & 15 watts but the amp defaults to diode rectification on 30 watts.

Change the Rectifier tube and you should be good to go.

Also, good info to know for those who use the amp a lot on 5 & 15 on the gig. If your Rectifier tube goes on the gig you can switch to 30 watts and still finish the gig!

Let us know how it goes an hope this helps.



Tim September 28, 2012 at 1:16 pm

Damned if I didnt ask that! Various “techs” and salesmen didnt know if that could be it either . . .

Thanks for answering quikly – I’ll see if I can find one on the way home.

I LOVE this amp, one of the bst purchases I’ve made ever. Really.


Andi February 22, 2013 at 2:20 pm

Dear Boogie,

thanks a lot for giving hints like that. After blowing the first fuse yesterday, I thought: ok, can happen. But today I got a new fuse and I blowed it again after 1 hour in 5 W mode. Now 5 and 15 W modes are not working anymore and I got really worried about having a serious damage. I tried different tubes in the outer positions but still not a single tone except in 30 W mode. Thanks to you I now know exactly what to buy tomorrow to get my beloved amp working again!

Best regards from Austria,


Joshua June 16, 2012 at 2:45 pm

I’ve had a Rect-o-verb series 2 for about 10 years now and have been the only owner. A while ago my brother was playing it and it just shut off on him, so we checked the fuse and sure enough it was blown. I replaced the fuse, and it immediately blew again when I turned the amp on. After this, I replaced both of the power tubes and the fuse. I turned the amp on, and after about 30 seconds the amp shut off again and a little smoke came out from somewhere around the tubes. I noticed that some of the plastic around one of the pins on a tube was burnt, so I looked at the circuit and noticed that there were burn marks on the tube socket as well. The particular pin seems connect straight to the output transformer via the brown wire. Nothing else “seems” to be noticibly burned (i.e. resistors). Do you think their could be a problem with the transformer?



Boogie Boogie June 18, 2012 at 4:57 pm

Hi Josh –

Sorry to hear of the problems with your Rect-O-Verb.

Sounds like when the tube failed the first time it arc’d in the socket and probably left some residue/carbon in the socket that needs to be cleaned up and there may have also be damaged screen/grid resistors when the tube failed. These things will need to be addressed and the amp should be looked at by an authorized technician before moving forward. Either or both of these things may be what caused the fuse to blow the second time and changing failed power tube components in the case of a more extreme tube failure like this is not a user-serviceable job like just changing the tubes. These kind of tube failures are not the norm but do happen and fortunately, cleaning the socket and changing a few resistors is an easy job for an authorized tech that won’t break the bank and the tech can go through the amp as well and give a clean bill of health and get you back on the road.

Check out the list of Authorized tech’s here in the US:


And for folks outside of the USA, here’s a link to Mesa distributors who can direct you to your nearest Authorized Mesa repair outside of the USA:


Hope this helps. Let us know what you find out once repaired.



Lou June 15, 2012 at 5:49 am

Hello I just bought and recieved my Mesa Boogie Dual Rectifier, I have never owned a tube amp before I wanted to know how exactly to use the standby feature when turning it on and off? Do you turn the amp on first and then switch the standby switch to on as well? and when turning it off do you flip the power On to off first or Standby On to standby first? Just want to know exactly so the amp tubes and fuses last me a long while, the amp sounds amazing thanks for your help!


Boogie Boogie June 18, 2012 at 11:06 am

Hi Lou –

Great question and one everyone operating a tube amp should know. It’s also spelled out in your manual but easy to describe here.

ALWAYS power up with the standby switch down. Allow the amp to warm up for at least 30 seconds before lifting the standby switch up. Longer is OK – shorter increases chances of more significant wear on power up or possible shorting/failure.

Contrary to popular belief it’s the powering up and down that generates the most wear on the tube in comparison to hours of loud playing.

When power down, turn the standby down and allow the amp to settle for at least 5-10 seconds. Get in the habit of turning the Standby down first before the final power down as it also makes it so when you go to power up again the Standby is already in the down position where you want it. powering down doesn’t require 30 seconds but you can power down this way for whatever duration you want.

Hope this helps!



Jack June 8, 2012 at 8:00 am

Hi. I have some maybe stupid question but I didn’t find any answer for it. I just bought used Mesa Boogie Dual Rectifier on auction but I’m not sure if it is USA 110V version or Europe 220V version. Where can I check it? I dont want to plug it in and destroy it.


Boogie Boogie June 10, 2012 at 10:35 am

Hi Jack –

The voltage of the amp is always written/printed next to the AC cord where it goes into the amp or if a newer amp, the IEC cable input jack. Hope this helps.



alex May 3, 2012 at 4:49 pm

Hello I have recently blown a rectifier tube in my dual rectifier (3chanel) but before I realized that, I thought it was just the fuse that had to be replaced so that’s what I did the obviously y caused the new fuse blow again but this time smoke came out of the front panel of the amp the kinda scared me out I hope nothing else got severe damage.

Now I’m going to replace the rectifier tune and the fuse, my question is, can I just replace the one tube or do I have to get both of them?

And also do you thing the smoke coming out was a normal reaction or can definitely be something worst?



Boogie Boogie May 7, 2012 at 4:07 pm

Hi Alex –

Sometimes when power or rectifier tubes fail and depending on HOW they fail, they’ll take out a resistor that regulates the voltage that gets through the resistor to the tube. It’s kind of like a voltage backlash and because the tube shorts it sends the voltage back to the resistor and ‘takes it out’.

In this case, the tube, the resistor and the fuse will need to be replaced and the resistor being replaced is something that should be handled by an authorized technican and is not user serviceable. Fortunately, a resistor failing when a tube goes is much more rare but does happen when a tube fails/shorts in a certain way. That said, it’s generally an easy repair and while requiring a tech can be handled pretty quickly.

As for one or both tubes being replaced, if your tubes were not very old (6 months to one year) we would just recommend you replace the one. If your tubes are older or have never been changed since you’ve owned the amp you might replace both and save the one that didn’t fail as a spare.

Hope this helps.



alex May 8, 2012 at 10:15 am

Thanks a lot for the quick response I will definitely have a technician take a look at it and yeah the tubes are way older than that so I will have both of them replace then.


Adrian M April 29, 2012 at 9:36 am

I have a problem here… My bleoved 1991 Mesa Boogie Mark IV won’t Power ON eventho i’ve checked the Fuse and it seems to be okay.I was using that about two weeks ago and it was working fine.
I’ve tried FULL POWER and TWEED POWER with no results so I think that either something iside is “fried” or maybe power cord is broken inside the isolation or maybe tested fuse is not really working.
I would like to add that the amp is Europe version and im using it in UK.

Could you please help me in that matter as I really love this amp and selling it is not an option even if I have a modeler.



Boogie Boogie April 30, 2012 at 11:39 am

Hi Adrian –

The key words in your inquiry are “seems to be OK”…

Because fuses either work or they don’t, visual inspection is not always a guaranteed approach. While a fuse may look fine, the connection from end to end that makes the fuse a fuse may be compromised in the end cap where you can’t see it and the only way to confirm the fuse is good is to test it with a multi-meter.

If you don’t own or have access to a multi-meter, getting a new fuse is the next best thing. Other than a fuse, no power can suggest a few other issues that ultimately will have to be looked at by a technician. Chances are good it’s just the fuse but if not, contact your nearest local authorized Boogie technician for them to have a look.

Good luck and hope this helps.



Marek April 24, 2012 at 6:17 am

My roadie accidently plugged my 110V Rectoverd into 220V. He is dead (roadie) unfortunetly my amp is as well.

Should I just replace the main fuse and see if it works? What kind of damage are we talking about?


Boogie Boogie April 24, 2012 at 9:58 am

Hi Marek –

This is generally not a good thing. You can try replacing the fuse and seeing if the amp will power up as it’s possible the fuse blew before damaging voltage reached sensitive parts in the circuit. This mismatch of voltage has a potential to permanently damage the power transformer requiring the transformer to be replaced.

Best of luck.



Marek April 24, 2012 at 11:27 am

Thanks, I will plug it in to see whenever my Mesa is still alive


Marek April 25, 2012 at 7:18 am

Me again!

My amp is alive!!!

Quick question. My step down box (220V-110V) is 300W output.
Is 300W enough for my 50W Single Rectoverb head or shall I look for more powerfull one?


H Nasution March 23, 2012 at 11:05 pm

Hi, I sold an organ to get myself a used dual recto. Problem is, the slo-blo fuse is toasted & i couldn’t find those @ the local electronics shop. The closest i could find is the 5A slo-blo. Is it compatible? Im from Malaysia & your designated dealer, Bentley Music also do not have the stock. Advise please, im @ a dead end here.


Boogie Boogie March 24, 2012 at 8:37 pm

Hi H –

ALWAYS use the SAME value of fuse as a replacement in ANY amplifier or electronic device. NEVER!!! use a fuse of a different value from the one rated on the amp near the fuse holder. Extreme damage to your amp may occur if you do not use the proper rated fuse in the amp. If this is not clear, please read the article again as it explains why this is so important and it’s really an important thing to be aware of when operating tube amplifiers. The distributor servicing and selling products nearest you should have the proper rated fuses you need and you can often find the fuses you are looking for at electronic supply stores as well. Let us know if you have any problems with finding what you need. Also, make note that you’ll likely need to do some tube troubleshooting once you get new fuses. Keep us posted.



H Nasution March 27, 2012 at 6:22 pm

Hi Dr Boogie,
Appreciate ur reply. Is it possible that, my problem of finding a suitable fuse for my Recto is that it is an imported model, 1 that needs a step down tranny. Ive checked with our local dealer (Bentley/Malaysia) & they said they stock different value fuses. Anyway, Ive managed to source a couple from Nick of ceriatone, thank heavens.


Boogie Boogie March 28, 2012 at 6:17 pm

Hi Harris –

If your amp is a USA version that you are attempting to operate outside of the USA, this would be a reason why fuses are more difficult to find, especially from your local distributor. Distributors stock parts & fuses for amps of proper voltage operation in their regions/countries. Sourcing fuses for 117V amps in countries whose voltage is 220-240V is, indeed, probably more difficult as the fuses are different sizes.

The fuses themselves are not rare by any means but different ones are used based on the countries voltage and there would be little reason for any entity in a given country to stock fuses that none of the electronic devices in that country are designed to operate properly with…

Hope this helps and best of luck getting the amp back up to speed.



Richard March 21, 2012 at 9:01 am


I have a mesa mark iv and I have just one silly question; I run it in class A mode with el-34 in the outer sockets. The thing is that in this mode, only the outer pair of tubes are active, but all the power tubes are glowing. The middle pair,though glowing, do not get as hot as the two outer tubes. Any cause for alarm?

Best Regards



Boogie Boogie May 7, 2012 at 3:51 pm

Hi Richard –

With any Simul-Class amps or amps with wattage selection options, even though the tubes are not in use they still remain lit. The filament of the tubes remains lit but the other operations of the tubes are in a standby state. This is the normal operation and because the only the filament is lit those tubes will run cooler.

Hope this helps!



Zach March 3, 2012 at 7:00 pm

My Boogie Dual Rectifier just won’t turn on. We used it last while recording and it worked fine. a few days ago, I went to turn it on and it wouldn’t. I tried different power cords and different outlets and nothing. Could replacing the fuse fix this because the amp was off?


Boogie Boogie March 5, 2012 at 3:54 pm

Hi Zach –

If you’re amp doesn’t power up the first place to look is always the fuse. Sometimes the fuse will blow so fast that you don’t even see the pilot light turn on.

In any case, the first place to look is the fuse, remove and inspect it to see if it’s blown or replace it with one of the exact same value and let us know what you find.

Hope this helps.



Vince February 10, 2012 at 5:44 pm

If the pre-amp tubes don’t cause a fuse to blow what would the case be if you use a rac- mounted pre-amp only with pre-amp tubes ?


Boogie Boogie February 10, 2012 at 6:16 pm

Power surge just enough to blow a fuse or possibly a power surge which may cause damage beyond the fuse if the fuse doesn’t blow in time. Do you have a rackmount preamp with a blown fuse?


Shorne February 2, 2012 at 7:41 pm

Hey, I’m saving up for a Dual Rect or a Mark V, but it seems I will be spending most of my time in South Korea. The voltage in the US is 110 and the voltage over here is 220; is a transformer the only solution?

It’s not really the transformer hassle that botheres me, it’s the fact that transformers can shorten the life or even cause problems on whatever’s connected – I do NOT want anything to go wrong with these amps/cabinets when I purchase them.

Thanks Mesa dudes.


Boogie Boogie February 7, 2012 at 6:51 pm

Hi Shorne –

You should always buy your amp with the voltage at which it will see the most use. Understanding voltage differences is crucial for proper, reliable operation of any electronic device. The safe bet is to always operate the amp at it’s original intended voltage for the country you live in/spend the most time in and to purchase products designed to operate at your home countries voltage. Mesa does not and cannot provide information on external transformer operation. Please contact your home countries distributor/dealer for further information on availability of amps in your host country and any voltage considerations you may have.


Hope this helps and hope you’ll be able to get into a Dual Rec or Mark V soon! ;)



Toto January 16, 2012 at 10:04 am

Hello, can American Mesas (domestic) run in Europe? Or I have to buy another for European gigs? Thanks!


Boogie Boogie January 27, 2012 at 9:05 pm

Foreign voltages are frequently different from USA voltage. Plugging a USA voltage Boogie into a European voltage supply can cause SIGNIFICANT damage to your amp. Never plug a USA voltage amp into a European supply.

If you plan to move or live in Europe, it’s recommended to purchase your amp from the Authorized Mesa Distributor in the area/country where you’ll live to insure proper/safe operation. You can also contact that same distributor about getting your amp converted. Mesa’s distributor list is here:


If you are a touring musician playing infrequently abroad but living in the US and with a USA voltage amp, there are options for professionally converting the voltage to operate your USA made amp with Export voltages temporarily and, again, you would contact the local distributor in your country for more info. Hope this helps.


Maj December 20, 2011 at 1:02 pm

hey guys
I did a very stupid thing the other day.On my rocket 44 ampak i pressed the button fuse while the amp was active and i didn’t intend to change the fuses or whatever this does.
Now my amp went i turn the volume up does strange noises,but not that i can’t play when i have my volume up on my guitar it kidna renches,but when i close it it’s silent.
Any advices?i would preffer that it isn’t necessary not to switch the fuses :)


Boogie Boogie January 2, 2012 at 2:03 pm

Hi Maj –

Hard to say what is going on with your amp or setup at this point.

Obviously, when the amp is on and working properly, there is no reason to engage the fuse.

I would remove and re-install the fusecap to make sure it’s properly seated on the amp but beyond that, the fuse can’t easily be responsible for making noises in the amp. That is likely coming from something else. Remember-fuses don’t “cause problems” they either work or they don’t and when they don’t, it’s because something else in the amp caused the fuse to fail.

Hope this helps.



M December 10, 2011 at 12:28 pm


My Simul-class 2:90 had new tubes installed about six months ago; two new ones to be exact.

It was working perfect two days ago, then I plugged it in, and POOF! No lights, no power-nothing…

So I checked the fuse and it looked blown (brown burn mark and broken little wire in the glass). And if it was, what on earth could be causing it to blow? I am thinking it was a power surge but I was using a power conditioner…. Am I dealing with some bad tubes again? Is it possible that the tech put in some bad tubes?

I am replacing it but I am confused; 4Amp or 6 1/4 amp?


Boogie Boogie December 12, 2011 at 6:26 pm

Hi M –

Like the article says, when a fuse blows, it’s trying to tell you there’s something wrong in the amp. In this case (and most fuse blowing cases), it’s most likely it’s a power tube.

It’s more likely that the next weakest link of the tubes you DIDN’T replace failed.

If you know that the tubes in your amp have a lot of use and wear on them (and it’s time to change tubes), it’s generally recommended to change them ALL at the same time. If you’re unable to do that, it’s fine to change just the known bad ones but… If a set of tubes has significant use on them, the first to fail is often just the weakest link signaling more failures could happen.

Power conditioners do not protect the amp from tube failures and they may not always protect your amp from power surges either.

It’s possible that the new tubes failed as well because no manufacturer or tube reseller has a way of testing how long a tube will last. this is why anyone that sells tubes (worth their cost, anyway) has a warranty. If a tube last 6 months, it’s likely to last it’s full lifespan which is why we have a 6 month warranty on our tubes (one of the best in the business, by the way…) ;)

It’s unlikely that a tech put in bad tubes because if they were bad, they would have failed immediately. A tube that works is a good tube until it fails…

If you have an older 2:90, there are potentially 3 fuses. The one in the front , for USA models is 6 1/4 amp Slo-Blo. There are also 1 amp cathode fuses on the back of the amp. Sounds like it was your 6 1/4 amp fuse. All fuse requirements will be clearly printed next to the fuse holder where the fuse lives. Always replace fuses with the EXACT value stated on the amp near the fuse location or in the manual. Failing to do this can result in excessive damage beyond inevitable tube failures.

Hope this helps. Let us know what you find.



M December 16, 2011 at 8:14 pm

Ok, so I replaced the fuse w/ another 4 1/2 amp fuse, for now. I will be buying a hand full of the 6 1/4 amp fuses from mesa next week.

But the 2:90 is acting all screwy…

Two days ago, when I was playing at a medium-loud volume, when I used the “deep” voicing (using a separate switch, NOT the triaxis), the “deep” voicing was LOUDER….I mean, it was LOUD and DEEP, and much more so than when the “deep” light is out….then, yesterday, I used the “half” setting…and everything was fine until today, where I plugged the switch back into the “deep” setting…and this time the volume was WAY lower than it was the last time I used the “deep” voicing! I wound up using the basic voicing and it sounded nice and loud with a lot of drive. But the “deep” voicing sounded almost exactly like the “half” power…

Does any of this make sense? Two days ago it was working fine….and now, it’s screwy. I man, with the “deep” light OFF it still sounds as it should-which is a TON of power and drive-while when the light is ON it sounds really weak and pathetic-like it was on half power, even though the switch is plugged into the “deep” voicing.

Am I doing something wrong here? Can you advise?


(I will some day own that Tri-Axis….)


M December 17, 2011 at 11:09 pm

How is this for confusing….

NOW, when I went to a recording session the power amp worked PERFECTLY without any issue whatsoever with the “deep” channel.

Not only did it work, but man…this thing blew the doors off the studio I was at. The poor fellow who was engineering never heard something so powerful and loud.

So I don’t know what direction to take here: is there or isn’t there something for me to be concerned about? The thing sounds like a bast from the blackest abyss and I don’t want to mess with that unless there is a hidden problem I don’t know about…

Maybe there is a slight short in the circuitry? I doubt if the tubes are bad if we are driving this thing at at least 50% volume in either of the channels for 3 hours…


Phillip December 1, 2011 at 2:36 pm

ok.. first and foremost.. yes.. im a dummy.. i plugged my stiletto on a 220v accidentally.. and that major power surge blew my fuse.. i just wanted to know.. (just to relieve myself) is the fuse the only damaged component or probably there is something more inside that has been affected.. cause i saw a very little amount of smoke coming out at the fuse section.. thanks i hope it didn’t blew more things inside


Boogie Boogie December 1, 2011 at 7:56 pm

Hi Philip –

It’s impossible to say if the problem is ONLY the fuse or if your power transformer was damaged as well. There is also a secondary internal fuse on the power transformer that will also fail in a power surge or overvoltage situation. This component is called a Varistor and is generally something a technician will check or change in wrong voltage situation like yours.

You can try to change the fuse and power the amp up with the proper voltage but in most cases like these or any case where you see smoke from the amp, we suggest the amp be taken to a technician who can go over the amp thoroughly to avoid further damage to other components and parts of the circuit.

Hope this helps and keep us posted on how things went.




phillip December 4, 2011 at 12:57 am

thanks sir.. its already fixed now.. just wondering also.. how will i know that one of my 12ax7 tubes is dead?

thanks a lot again


Boogie Boogie December 6, 2011 at 3:29 pm

Hi Philip –

Glad the amp is fixed. What was the problem/fix?

When 12AX7 preamp tubes FAIL, the result is usually NO sound or a VERY small amount of the original guitar signal (1%) being amplified. Because preamp tubes are lower voltage than power tubes, they will never be the cause of a blown fuse. Preamp tubes can also fail by becoming weak but still working. Your sound may still be quite loud but, in general, lack punch and brightness, detail or other characteristics. There are many different ways tube failures present themselves but these are the main two. If you combine these responses with a good knowledge of how old the tubes are (which will help you know when it might be time to change them), these are the best ways to troubleshoot and maintain tubes and the preamp tubes in general.

Hope this help!



JamesOsyris November 22, 2011 at 3:00 pm

Also, if I do change a tube, how do I bias them? And should I do it myself?


James Osyris November 22, 2011 at 2:43 pm

I just had my Dual Rec go out. I turned it out, and it sounded muddy for a good minute while I struggled to find the problem. I switched guitars, and turned the volume up a bit, and it zapped and went dark.

I’ve read this page pretty extensively. The one problem I have is that I have my fuse in front of me, and it’s not black like everyone is saying it should be when it goes out. Also, where can I buy fuses that are 6A 250V? And are they supposed to go in a certain way like a battery?

None of my tubes are black. If I switch the fuse and turn my head on in solid state without the tubes on, should that tell me if the tubes were the culprite?


Boogie Boogie November 23, 2011 at 7:20 pm

Hi James –

Sorry to hear about the problems with your amp. The first and most important thing to be aware of is that a fuse rated or labeled 6A is BAD for a 117V Dual Rec. The proper fuse for a Dual Rec designed to run at 117V is 4A. If you had a 6 amp fuse in an amp that requires a 4 amp fuse, its possible that there is damage beyond just a power or Rectifier tube having failed.

Fuses should be able to be purchased at an Electronic Supply store, and if not there, possibly at an automotive supply store.

Regarding tube troubleshooting, I must suggest you watch the Mesa tube troubleshooting video for more detail on how to troubleshoot bad tubes:


This video should answer most of your questions regarding the troubleshooting process.

Regarding bias, all Mesa amps have a fixed bias which is not adjustable. If you are using Mesa tubes, the tubes are tested to work perfectly with the fixed bias in the amp – no bias adjustment is needed. Plug em in and you are ready to go. The fixed bias of the amps makes it so you can change tubes yourself – just like changing a light bulb.

Hope this helps and let us know what you find out.



Tom November 11, 2011 at 7:13 am

My M-190 recently blew a fuse, and after replacing it, the output has been dramatically reduced and the sound is completely distorted. All the tubes light up. Any ideas? Thanks


Boogie Boogie November 11, 2011 at 9:23 pm

Hi Tom –

Following the concepts of the post, your next step would be to consider that one or possibly some of the tubes in the amp are bad. The amp may run after changing the fuse but the fuse was never the problem – just the sign that something was up… Something caused the fuse to fail and the usual culprit is a tube.

Since preamp tubes don’t run at high enough voltages, its more likely there’s a bad power tube. If you haven’t changed tubes in the amp and logged a bunch of hours on them, it may be time for you to change tubes across the board…? If they are farily new or not used much, perhaps just getting a pair of tubes and changing the tubes out in pairs will reveal the failed tube(s)?

Next for you is tube troubleshooting and you can gain some insights into that process by viewing this post and the video within:


Hope this helps and let us know what you find.



Tom November 13, 2011 at 12:50 pm

Hi Boogie,
Thanks for your reply.
I put in a spare set of power / rect. tubes, and I get the same problem.
I’ve had 2 people tell me it could be either the output tranny or the power supply bias.


Boogie Boogie November 14, 2011 at 12:18 pm

Hi Tom –

Unlikely in our opinion. Mesa amps have to REALLY be abused to experience Output transformer failures. Since the bias is fixed, it’s unlikely to ‘drift’ or change although it is possible for bias related components to fail/change and cause for a difference. HOWEVER – this is also more unlikely. The most likely issue is the tube(s) that failed burned up a screen resistor on the socket and need to be replaced.

Regardless of what it is, it is unlikely to be anything user serviceable at this point. Your amp should be taken to to Mesa authorized repair to have them go over the circuit and check out the tubes etc.


mike October 19, 2011 at 10:03 am

HI there, just experienced blown fuse in my Dual Rectifier as well. The problem is, first time: I´v tried to replace fuse and it was immediately gone again. Though it was bad tube, I have tried to pull two of them out, replaced fuse..but now, when powering on…no lights on as well, then I´v put those two tubes back and nothing, amp seems to be dead?…new fuse is on but amp will not turn on?..could something inside the amp got damaged badly?:.

another question is, should be amp working with les than all tubes? actually, this Mesa has 4x6l6, if one is gone, guess it should work on 3 with no problem,am I right…

can be problem somewere else, ..power, transformer etc.

many thanks


Boogie Boogie October 19, 2011 at 3:26 pm

Hi Mike –

When the fuse blows, it is almost always trying to tell you that there is a bad tube in the amp – Except when there is more extreme damage to transformers, resistors related to the tubes or possibly the varistor in the amp which protects the amp against extreme power surges/spikes. BUT – the first thing to always rule out is the tubes themselves and they are the main reason the fuse exists in the amp in the first place (and the main reason for the troubleshooting video you likely just watched ;) .

Make sure to watch this troubleshooting video closely as it will walk you through the troubleshooting process you need to employ to either fix the amp via tube replacement or rule out that tubes being the fault.


If you removed ALL power tubes and the fuse still blew, it’s likely that the problem is actually one of the rectifier tubes, not one of the power tubes. Both rectifier and power tubes can be a cause of a blown fuse so removing the right tubes and replacing the fuse is really important. The video goes over the proper troubleshooting to weed out which tubes might be the problem so if you weren’t aware that it’s rectifier tubes that may be causing the problem, you might want to take a look at the video one more time.

It’s always possible that something else is the issue although transformers have to be absolutely tortured to fail for good and often times heavy smoke or electronic burning smells with precede this. We see VERY few transformer failures. As for using less tubes, you should always have matched pairs in appropriately matched sockets in the amp. The following info deals with tube pulling and matching in a Triple rectifier which is the exact same concepts as a Dual but 2 less power tubes and 1 less rectifier.

As for which tubes to remove… If you label the POWER tubes from left to right, 1 through 6, the tubes are matched in pairs as 1 & 6, 2 & 5 and 3 & 4. Remove any one of the matching pairs and you will have taken your amp from a 150 watt to a 100 watt.

HOWEVER, YOU MUST ALSO MAKE SURE (in caps because this is VERY important) to move the speaker connection to the proper jack on your amp once a pair of tubes is removed. Failure to do so may result in damage to your tubes and/or transformers. Do not fail to get this right!

When you remove two power tubes, the impedances of the speaker jacks the back of the amp DOUBLE. The 4 ohm jacks become 8 ohm, the 8 ohm jacks become 16 ohm, etc. If you have one 8 ohm cab, you would now connect it to ONE of the 4 ohm jacks to be properly/safely matched with 2 tubes removed. If you have more than one 8 ohm cab, you’re in trouble because you don’t have any 4 ohm jacks anymore. Besides, if you have more than one ohm cab, you can probably use the power anyway…

As for removing Rectifier tubes, removing any ONE is fine (with 2 power tubes removed) – the location is not important. If you only use the amp on Silicon Diodes, you can leave all 3 Rectifier tubes in but if you accidentally switch the amp to Tube Rectifier with only 4 power tubes in a Triple, it’s not the best thing for the amp.

Hope this helps and look forward to what you find.




Mike October 20, 2011 at 8:17 am

well, many thanks..

I have not tried to check rectifier tubes – guess, it might be the problem or maybe not,
however, maybe I screwed it up..as, now, even with all tubes out and new fuse, amp will not simply turn on. I have red few thing that should not be done and I do remember, last time I was changing the fuse I forgot to plut speakers into amp. I remember the fuse blew immediately within second but ever since, no response from amp at all..

do you think it can be blown tranformer? as I am afraid it might be, for even with no or damaged tube, the amp should still at least ligh on stand by..correct?
I’d better take to my tech… but it will take weeks



Boogie Boogie October 20, 2011 at 12:30 pm

Hi Mike –

With no tubes in the amp, if the amp doesn’t power up this is generally something that a technician will need to look at.

Just powering the amp up with no speakers plugged in is VERY unlikely to damage transformers. Transformer damage generally only occurs with guitar being plugged in but no speakers plugged in, OR – a significant power surge which, ironically, is also rare to cause transformer failure because there are components inline with the AC in which will protect the power transformer from a surge.

Make sure you are using the correct value fuse. If the fuses you are using are underrated, they will blow instantly leaving you to think that something else is wrong. If you didn’t play the amp for an extended time with no speaker connected and nothing else extreme happened, it is likely a minor component failure that a tech will find and fix easily.

Let us know and best of luck.



keith September 24, 2011 at 12:08 pm

I have a Mark II power amp that I havent used since it blew a fuse 15 years ago. I head another amp that Ive been using since and didnt need it. So I pulled it ouot of storage today to try and figure out whats wrong with it and found that it keeps blowing fuses even when I remove all the tubes.. Is this a power transformer failure or is there something else it could be?


Boogie Boogie September 26, 2011 at 1:58 pm

Hi Keith –

If the fuse blows with all the power tubes out of the amp, chances are good there is damage to the transformer. Not every time sm a trip to an authorized tech or sending the amp back home to the factory is the next step in getting the amp up and running.

Give the factory a call to discuss further if you’re interested.


Brian September 9, 2011 at 5:28 am

I have a 2:100 power amp that the sound started cutting out.
Sometimes completly and other times the bottom end(maybe 1 channel missing).
I though it was a bad cable. As when I move the input cables(sometimes unplugging and plugging in) it would kick back in.
Now that only works sometimes.Other times I can turn on stand by and back off and it is good.Other times I power down and turn it right back on and its good.
It may play for an hour or longer before it does it.Last night it happened 8-10 times in 2 hours.
Any ideas?


Boogie Boogie September 19, 2011 at 11:40 am

Hi Brian –

This is more likely to be a preamp tube inside the amp.

Does the problem happen on both channels or only one and do you use both channels? When was the last time you changed the tubes?

The problem has likely fixed itself because the physical vibration that you caused when you changed cables actually caused a hairline short in one of the tubes to reconnect and the problem went away – until the tube got hot enough to hairline short again.

Tubes can be finicky that way and make the troubleshooting process a little finicky but taking the time to change the tubes one at a time and see which ones might be the cause, especially if you haven’t changed tubes for a while, is the way to figure it out.

The 2:100 has a preamp tube each that is the driver tube and a another tube that is shared between the two channels. If the problem is on both channels you would suspect the shared tube. If the problem is in a specific channel, you would suspect the preamp tube that is closest to the bank of power tubes relating to side A or B. Make sense?

Hope this helps – let us know if you get it.




paul September 5, 2011 at 11:54 am

hi….just wondering if moving a amp while its on stanby could cause the fuse to blow….also i had the amp on standby for quite a while ..about 4 hours…so i was wondering if it could have been that either…

could you please tell me the type of fuse i need ,,,its a UK mk4


Boogie Boogie September 8, 2011 at 4:51 pm

Hi Paul –

Keeping in mind that fuses fail when something else goes wrong in the amp, first and foremost, it’s much more likely that a failing/shorting tube caused the failure and not the fuse itself. The fuse blew because a tube failure caused it to blow!

The more specific answer to your question about whether or not moving an amp could cause a tube to short (given the discussion above), the answer is it’s definitely possible. The amp being on standby for 4 hours is only a very slight possible contributor but the bigger questions are, how old are the tubes? When were they last changed and how much use have they seen since being changed? There’s no way to know when a tube will fail which is why understanding troubleshooting is so important.

If your tubes were older and have seen many hours of use, the movement of the amp and standby are of no consequence to the failure. It was just one of the tubes times to fail and now it’s time for troubleshooting, finding the bad tube, replacing it – OR deciding that it’s time to replace all the tubes in the power section or perhaps re-tubing the whole amp.

The fuse value is always noted on the back of the amp near the fuseholder itself. It’s either printed on the chassis right next to the fuse or on a sticker next to the amp. Because fuse values can and have changed on different models, it’s important to identify what’s needed on the back of your amp first to make sure you get the fuse your amp was originally designed to use.

Hope this helps and hope you’re able to get your amp back up and running to it’s originally glory once the tubes are troubleshot and changed!




Ryan Morawski August 29, 2011 at 3:55 pm

I have a question it seems your the man who can answer. My preamp started peaking at high levels in my recording software before it blew the fuse. I tried replacing the fuse and it blows instantly i have had this preamp for years and never changed any tubes…..it takes a 12axt and a 12au7 are either of those the problem?


Boogie Boogie August 31, 2011 at 12:52 pm

Hi Ryan –

Preamps aren’t usually high enough voltage to blow a fuse although without knowing what you’re preamp is, it’s especially hard to say. Given that the unit was peaking before the fuse blew, it sounds to me like there was a voltage spike which may have caused some damage to the unit well beyond tubes. I suggest the unit be taken to qualified repair to be looked at. It’s unlikely that your problem is just tubes.


Den August 20, 2011 at 5:25 am


This is the thread I have been searching for. Really informative & helpful!

I recently bought a 6SN7 tube processor. It’s placed between my DAC & AMP. I’m using it in 220V. The manufacturer states 0.5A fast blow fuse X 110V = 0.25A fast blow fuse X 220V. I’m having a tough time using a 0.25A fast blow fuse in 220V. It keeps blowing up at power up & I’ve already blown three fuses. I’m currently using a 0.5A fast blow in 220V with no issues at all though it’s not recommended by the manufacturer.

I’d like to know what w’d be a better choice for me, a 0.25A T (slow blow) or 0.5A F (fast blow) Fuse? I wrote to the manufacturer & they have not even bothered to reply.

Any information will help me make the right decision.

Many thanx,



Boogie Boogie August 31, 2011 at 1:07 pm

Hi Den –

Being that this is not a Mesa amp, we are not really qualified to make suggestions. However, what is very important to understand is that the suggested fuse rating on any electronic device is generally NOT flexible. If you understand that the fuse is in the amp to fail in time to protect the rest of the circuit, then you will also understand that when the fuse fails, it is trying to tell you that something is not right. Whether it’s the voltage provided to the device (over voltage?) or component failure, it’s VERY important not too exceed the recommended fuse value. Doing so can result quickly in very expensive repairs and in extreme cases, complete failure beyond repair.

In your situation, we must recommend you contact the manufacturer for further details. Sorry we can’t be of more help.




Ponnari August 7, 2011 at 12:34 pm


This may be a stupid question but I have mesa 400+ and I lost the fuse holder cap. Can I use any AGC type of fuse holder cap to replace it or do I need a specific type of cap? Thanks


Boogie Boogie August 8, 2011 at 11:56 am

Hi Ponari –

The fuse cap is a fairly standard one that you may be able to find at higher end electronic stores locally in your area. If you are in the USA you can order that part directly from the factory. If you are outside the USA, please contact your local distributor for your country which can be found here:


Hope you’re able to get the 400+ back on track soon!



Felipe Vianna July 27, 2011 at 11:49 am

I have a Mark V that I use at home for less then 15 hours/week and my fuse blew out (only 6 months of use). Then I read all the stuff on this page and followed the instructions showed on Mesa Channel at YouTube. Following all those steps I saw a arc on my rectifier tube, and continued testing the power tubes with all the switches on rear panel turned to DIODE. Then I realized that it is everything OK with the power tubes. The MarkV head seems to be working very well on Diode mode. My question is: Can i use the amp normally in DIODE mode until I replace the rectifier tube? I live in Brazil and i have to order some spare tubes. But wait a month without playing even in the Channel 3 would make me crazy.


Boogie Boogie July 28, 2011 at 4:38 pm

Hi Felipe –

On the Mark V, you CAN use the amp in 90 watts with no Rectifier tube working or plugged in (if you know the tube is bad it’s probably best to remove it!).

BUT… you must make sure to NOT switch the amp to any lower wattages in ANY channels if using the amp without a Rectifier tube installed – otherwise damage may occur!

You should be able to order a replacement Rectifier tube from the distributor in Brazil and hopefully get a tube much sooner than that. You can lookup their contact info here:


Let us know how it goes.



Felipe Vianna August 10, 2011 at 6:11 pm

I found the tubes at brazilian distributor. But I think here those tubes are very expensive!

Do you have any american dealer that can ship to Brazil?



Jiby April 3, 2011 at 7:41 am

Hi Mesa!
Reading this post makes me remember when I accidentally run my Mark V on without a speaker in.
I turn it on and hear no sound, so I try to turn the master up and still hear no sound. I immediately turn off and realize that there was no speaker.

The question is: would the fuse save the amp (i think the output transformer and power tubes) even from this accident?
My mark still sounds great :D it is just a curiosity (if one does not notice immediately there’s no load)



Andrew January 18, 2011 at 11:05 pm

Ok so sort of off topic but not totally. I was just changing power tubes and trying to locate a bunk preamp tube when just for kicks I figured I would pop the fuse out and look at it. Now that was no issue.. fuse looked fine.. figured as much.. but…. now I can’t get it to seat back into the back of the amp. I’ve never touched the fuse on the amp so I don’t know anything about it. Seems it sits inside the black housing with a metal casing. Do you push it in and twist??? it just keeps popping out and I have no power at all now!!!! I know this is basic stuff.. but I’m stuck. Anybody???


Boogie Boogie January 18, 2011 at 11:17 pm

Hi Andew –

The fuseholder is spring-loaded so you’ll need to push the fuse and fusecap into the holder with a fair amount of pressure. While pushing in, twist the cap until it locks and holds the cap in place. When you go to push it in, the base of the cap should almost touch the base of the fuseholder on/inside the amp, but not quite. That will be pushed in enough and all you’ll need to do is twist the fusecap (once in far enough) until it locks in place.

If this doesn’t help, give a call to Mesa customer service or write back here and we’ll get it figured it out.

Hope this helps.



Mike August 17, 2014 at 6:17 am

Old but important question.This happens often with the new fuse holders, they are being made differently than before. The metal catches are very thin and prone to damage whenever some one forces the fuse holder into the hole. The little metal catches, like hooks, are located on the removable fuse holder. These are supposed to ‘catch’ the hooks built into the fuse holder on the amp. If they are not catching, the fuse holder won’t stay in the amp, it just keeps coming out, and often pops out and gets lost! The fix is to take a tiny screwdriver and pry out gently on the catches, until the holder will operate properly. Replacement of the fuse holder with a more rugged design would be a good decision next time you are at the tech.


Joe December 22, 2010 at 9:33 am

I own a Mark IV which I’ve had for about 20 years. Recently my low voltage regulator went. I’ve had it successfully repaired by an authorized service center. My question..why didn’t the fuse blow? The amp smoked and the trace on my board had to be repaired. I was surprised that the fuse held? It is still the orginal fuse that came with the amp..never was replaced. The amp sounds great since the repair, just wondering for the future.


Peter November 14, 2010 at 3:38 pm

I have a Mesa Triple recto. Recently I blew a fuse on a gig. I got a replacement fuses and tried to run the amp again, but it blew the fuse immediately as I switched the power switch on. I checked everything, tubes seems ok, so does the whole amp, no smoke coming from anywhere…than I tried another fuse. Same problem again. I haven`t touched it since then. What could be wrong?


Boogie November 15, 2010 at 11:45 am

Hi Peter –

Its possible you may have missed one of the most important aspects of this blog post… ;)

“The fuse is in the amplifier to protect the amplifier’s circuit from tube failure and other extreme voltage issues!”

Understanding that the fuse is in the amp to protect the amp from tube failures is the most important aspect of this post. “Tubes seem OK” suggests that you might have only looked at the tubes and thought they were OK by visual inspection which is not a reliable troubleshooting method.

If you haven’t engaged the troubleshooting techniques that were linked in the blog post, that is your next step. If you don’t have much experience with tube troubleshooting, you are also welcome to call the Mesa customer service department and the gurus there will be happy to walk you through the process.

Its most likely that you have a bad tube in the amp that isn’t visually obvious and you you’ll need to engage the troubleshooting suggested in the manual and in the blog post links to find that bad tube, replace it, then replace the tube.

Let us know how the troubleshooting pans out, which tube you find that’s bad and if you have any questions. Sounds like an easy fix once you identify the bad tube.


Peter December 2, 2010 at 6:38 pm

Hi Mesa!
Thanks a lot for reply. I sure have read this blog before I posted, but I took the amp to tech. I didn`t want to screw anything, since I love my amp to death and I also got pretty scared when he told me: “Come and take it, I am not able to repair it. Tried tubes, they`re okay looks like a blown power transformer to me.”, so I wrote you here.
But after I got my amp I really wanted to make sure so I pulled all power and rectifier tubes out, turned power switch on and it worked. Then I tried to put all power tubes back, switched to diode rectifying and turned on…again it worked :D so the problem was a bad rectifier tube.
I guess the tech was just worried to try things with amplifier that is this expensive, since he`s not authorized mesa tech and he probably never seen this amp before. But at least he could tell me that he didn`t even touched it.
Anyway thanks for the greatest amps this world knows and also for your services and caring about your customers so much.
Cheers and all the best!!!


Jeremy John October 31, 2010 at 10:52 pm

Wow, man. I own a ROCK SOLID Mesa recto-verb combo, and the fuse melted. The info on the amp calls for a 117v and the local radioshack doesn’t really help info-wise. What do you mean when you speak of the difference between domestic and imported? Is 250v from the electronic store ok? Love your stuff, man.


Boogie October 31, 2010 at 11:53 pm

Hey Jeremy –

Take a look at the picture of the amp with the arrow in the post (it’s a Lonestar amp – stainless chassis etc.). That’s what you’re looking for on your amp.

The fuse value in a Recto-Verb is 2.5 amp but you should always check the back of the amp to make sure. If you live in the U.S. and bought your amp in the U.S., you’re amp runs on 117V. If you live outside of the U.S., in, say, Europe, Australia etc., you’re amp would run on 220-240V and would require a different fuse and since Mesa/Boogie (the one-and-only-factory) is in the U.S.A., we refer to 117V amps as ‘domestic’. Amps sold/run outside of the U.S. are referred to as ‘export’.

The fuse you need is 2.5 Amp, Slo-Blo. The 250V voltage is less crucial and you’ll nearly always find 250V fuses anyway here in the U.S.

Once you get fuses, it sounds like it’s time for some tube troubleshooting. Let us know how it goes!


Peter Turpin September 11, 2010 at 7:35 pm


My 6 month old Mark V head just blew a fuse. On average I play 7-10 hours per week at moderate volume. Is this normal? Should I try to replace the fuse and observe the tubes? I don’t want to do any serious damage to the amp I’ve been waiting for all my life!


Peter Turpin


Boogie September 13, 2010 at 6:00 pm

Hi Peter –

Sorry to hear of the fuse blowing. Tubes fail whenever they want to… So, as far as it being ‘normal’, yeah – it can happen on the first day out of the gates or 5 years later. This is why manufacturers offer warranties on tubes since no one can test tubes for how long they’ll last.

That said, the next step is to try another fuse although its a good idea to have some idea of what you’re looking for troubleshooting-wise when you go to power the amp up again. if you haven’t done this kind of troubleshooting before and you can call the Mesa factory at 707 778 6565 Monday-Thursday, 9AM-5PM Pacific time, one of the customer service gurus can walk you through the troubleshooting process and also get you set up with replacement tubes for the one that’s failed. They’ll teach how the troubleshooting for your model works and likely get the amp back up and running in the same call.

Looking forward to getting the amp sorted and back to its full potential.



Peter Turpin September 14, 2010 at 11:34 am


Thank you for getting back to me. I read through the article on tube failures, and I found the problem. After replacing the fuse I powered up the amp and noticed one of the 6l6′s had a “Lighting Storm” raging inside. I shut down the amp, and ordered new tubes. Hopefully my amp will be up and running tonight.

Thanks again for making the best amps on the planet, and for having great customer service.



ace September 3, 2010 at 4:58 am

Can you use a 240v slo blow fuse with the correct amp value? I cannot find 120v fuses.


Boogie September 8, 2010 at 11:40 am

Hi Ace –

Good question!

The fuses Mesa uses in all of its production, both Domestic (117V) and Export (220-240V) are rated at 250V.
The incoming line voltage of the amp does not affect the fuses voltage rating.
It’s important that the amperage rating of the fuse (EG: 2A, 4A, 8A etc.) and the Slo-Blo feature are correct. The voltage rating on any proper fuse will always be 250V.

Hope this helps.


Tony September 2, 2010 at 2:44 pm

I’m sort of new to my new Triple Rect. I’ve blown my fuse. Where do I buy a new one?


Boogie September 2, 2010 at 3:15 pm

Hey Tony –

Great question! Most Radio Shack stores in the US will carry Slo-Blo fuses and the 4 amp fuse in a Recto is a common value. However, if you don’t find one at a Radio Shack or other common electronic store like that, look up in your local phone book under Electronic Supply and call some of the biggest places. They are bound to have what you need. You can also call automotive parts places and they will likely have what you need as well if the Electronic Supply approach doesn’t work for your area.

Just keep in mind – these things are not rare… you just might have to call a place or two before you get the exact one you need.

Good luck and call Mesa Customer Service if you want some advice troubleshooting! Cheers.


Hassan August 14, 2010 at 12:13 am

I have a dual rectifier head that decided all of a sudden to not produce any sound although the lights are on…. Help!!!!


Boogie August 16, 2010 at 11:12 am

Hello Hassan –

If your problem of no sound is actually tube related, its most likely one of the preamp tubes having gone bad, shorted or otherwise not passing signal. Your first step will be to take one known good 12AX7 and replacing the tubes one at a time, starting with the preamp tube closest to the input jack. If the sound comes back as you replace a tube, you know the tube you replaced was a bad one. If changing a tube doesn’t fix it, put the old tube from that position back in its place and move to the next preamp tube position, replacing it – all in hopes of finding the one bad preamp tube.

The power or Rectifier tubes will rarely be a cause for no sound. No sound, if tube related, is nearly always preamp tubes. Power or Rectifier tubes are more likely to cause either a blown fuse OR muddy, reduced output and increased hum, just before they blow the fuse.

Hope this helps and if you have questions, feel free to call our Customer Service department for further troubleshooting 707 778 6565 – Monday-Thursday 9AM-5PM Pacific time – and we’ll be able to help get your amp back up to speed.


Canadian_F_H July 12, 2010 at 8:15 am

thanks! I’ve always appreciated how y’all are so forward with technical info. by comparison it almost seams like nobody else wants the player to know how to take care of his gear.


Chris McCown July 8, 2010 at 6:12 pm

I’ve never experienced a fuse blowing, I’ve played Boogie’s for about ten years now. I just wanted to say that although I knew most of what is in this article, it is a fantastic article, and I think I’ll go velcro a container of fuses to the inside of my Roadster head now, as well as put a label in it with the date of my last re-tube. Great advice guys! Thanks! Gotta Boogie now…


Jason June 23, 2010 at 5:17 pm

Been playing BOOGIE’S for 2 decades, and the only two times my Boogie’s blew fuses were my Mark Iv blew a fuse after a packing peanut got caught in the fan after shipping from Tacoma Washington to St. Louis, Mo. Second I had stereo Dual recto half stacks, one was ran through a furman power conditioner and due to lack of reach and my insisting a good distance between amps the other plugged directly into wall socket. Well it was storming during show and lightning caused fuse in Recto not plugged into the furman to blow. Thats not bad for 20 years of boogie use and some of it was my neglect. Mesa fan for life-Jason DeRo-


Boogie June 29, 2010 at 2:38 pm

Thanks for the comment, Jason. Appreciate you sharing the experience of many Boogie players. They just keep rockin’….


Tom DiNella June 17, 2010 at 5:44 pm

Great advice!Now ill tell this to my Roadie.Wait I am my Roadie.


Samuel June 16, 2010 at 1:43 pm

THANKS, good advice & Boogie……….


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