NOISE & MICROPHONICS:
may occasionally experience some form of tube noise or microphonics.
Certainly no cause for alarm, this quirky behavior comes with the
territory and the Tone. Much like changing a light bulb, you
don't need a technician to cure these types of minor user serviceable
annoyances and in fact, you'll be amazed at how easy it is to cure
tube problems...by simply swapping out a pre-amp or power tube!
First may we suggest that you set the amplifier
up on something so that you can get to the tubes comfortably without
having to bend down. It also helps to have adequate lighting
as you will need to see the tube sockets clearly to swap tubes.
Use Caution and common
sense when touching the tubes after the amplifier has been on as
they May Be Extremely Hot! If they are hot and you
don't want to wait for them to cool off, try grasping them with
a rag and also note that the glass down around the bulbous silvery
tip is considerably less hot which makes it easier to handle.
Gently rock the tube back and forth as you
pull it away from its socket.
POWER TUBE FAILURES:
There are two main types of tube faults:
shorts and noise. Both large and small tubes may fall prey to either
of these problems but diagnosis and remedy is usually simple.
If a fuse blows, the problem is most likely a shorted power
tube, Shorts can either be mild or severe. In a mildly shorted tube
the electron flow has overcome the control grid and excess current
flows to the plate. You will usually hear the amp become distorted
and begin to hum slightly. If this occurs, quickly look at the power
tubes as you switch the amp to STANDBY and try to identify one as
glowing red hot. It is likely that two of a pair will be glowing
since the "shorted" tube will pull down the bias for its adjacent
mates, but one tube may be glowing hotter - and that one is the
culprit. The other two are often fine - unless they've been glowing
bright red for several minutes.
Because there is no physical short inside the tube (just electrons
rioting out of control) merely switching to STANDBY for a few moments
then back to OPERATE will usually cure the problem... at least temporarily.
Watch the tubes carefully now. Should the problem recur, the intermittent
tube will visibly start to over heat before the others and thus
it can be identified. It should be replaced with one from
the same color batch, shown on its label. Call us and we will
send one out to you.
The severe short is not nearly so benign. In the worst cases,
a major arcing short occurs between the plate and the cathode with
visible lightning inside the glass and a major noise through the
speaker. If this is seen to happen, IMMEDIATELY turn the amp
to STANDBY. By this time the fuse probably will have blown.
Such a short is usually caused by a physical breakdown inside the
tube including contaminate coming loose or physical contact (or
near contact) between the elements. Replace it and the fuse
with the proper slo-blo type and power up the amp
using the power up procedure as we described earlier in this manual.
Often caused by contamination within
in a tube, the culprit can usually be identified, and by lightly
tapping on the glass, you will probably hear the noise change.
Hearing some noise through your speakers while tapping on the 12AX7's
is normal however. And the one nearer the Input will
always sound louder because its output is being further amplified
by the second 12AX7.
The power tubes should be all but quiet when they are tapped.
If crackling or hissing changes with the tapping, you have probably
found the problem. To confirm a noisy power tube, merely put
the amplifier on STANDBY, remove it from its socket and turn it
back on. It will cause no damage to run the amp briefly with
one power tube missing. You may notice a slight background hum,
however, as the push-pull becomes unbalanced.
Whenever you are trying to diagnose a suspect tube, keep your other
hand ON the Power and Standby switches ready to shut them off instantly
in the unlikely case you provoke a major short.
If you think you've located a problem tube but aren't sure, we
recommend substituting the suspect with a new one just to be sure
of your diagnoses. You will be doing yourself and us a big
favor by just following the simple guidelines previously mentioned
regarding tube replacement. You'll probably be successful with much
less effort than is required to disconnect everything and haul the
unit to a technician who will basically perform the same simple
tests. If the tubes are still within their six-month warranty
period, we will happily send you a replacement. Just note
the color designation on the tube label so
that we can send you the appropriate match.
PRE-AMP TUBE PROBLEMS:
Because your amplifier is an all tube
design, it is quite possible that at some point you will experience
minors pre-amp tube noise. Rest assured - this is no cause for alarm
and you can take care of the problem yourself in a matter of minutes
by simply swapping tubes.
Let us begin by saying; It is a "very good" idea to keep
at least a couple of spare pre-amp tubes on hand at all times to
insure uninterrupted performance. These minor pre-amp tube
problems can take many forms but can generally be described in two
categories: Noise and Microphonics, Noise
can be in the form of crackling, sputtering, white noise/hiss and/or
hum. Microphonic problems usually appear in the form
of a ringing or high pitched squealing that gets worse as the gain
or volume is increased thus are more noticeable in the higher gain
Lead modes. Microphonic problems are easily identified because the
problem is still present even with the instruments' volume off or
unplugged altogether - unlike pick-up feedback which ceases as the
instrument is turned down. Microphonic noise is caused by
mechanical vibration and shock: think of banging a microphone
around and you'll understand where the word came from.
The best way to approach a pre-amp tube problem is to see if it
occurs only in one specific mode or channel. Then refer to
the Tube Task Chart found on the sidewall of your cabinetry and
it should lead you to the tube needing replacement. Then all
that remains is to swap the suspect tube for a known good performer.
If you cannot narrow down the trouble to a specific mode or channel,
the problem may be the small tube that drives the power tubes which
is operational in all modes and channels. Though rare, a problem
with the driver tube would show up in all aspects of performance
- so if you can't narrow the problem down to being mode or channel
specific, you may want to try replacing the driver tube. Driver
problems generally show themselves in the form of crackling or hum
in all modes of performance and/or weak overall output from the
amplifier. Occasionally an anemic driver tube will cause the
amplifier to sound flat and lifeless, but this is somewhat uncommon,
as worn power tubes are a more likely suspect for this type of problem.
Sometimes making the diagnosis is more trouble than it's worth
and it's faster and easier to merely replace the small preamp tubes
ONE AT A TIME with a replacement known to be good. But MAKE
SURE you keep returning the tubes to their original socket until
you hit the one that cures the problem. You'll notice that
tubes located nearer to the Input jack always sound noisier...but
this is because they are at the start of the chain and their noise
gets amplified over and over by the tubes that follow. The
tube that goes into this "input socket" (usually labled V1) needs
to be the least noisy of the bunch. The tube that goes at
the end of the preamp chain - just ahead of the power tubes - can
be quite noisy without causing any problem at all. The tubes
in your amp have already been located in the most appropriate sockets
and this is why you should NEVER pull them all out at once and ALWAYS
swap them one at a time. ALWAYS return a perfectly good tube
to its original socket. Also it's a good idea to put the amp
on Standby when swapping tubes to reduce the heat build up in the
tubes themselves and to prevent explosive noises (which can still
occur even if you are pulling the tubes away from their sockets
gently) from coming through the speaker.
Remember, take your time, be patient and chances are real good
that you can fix your amp yourself by finding and replacing the
bad tube. It kills us to see someone who has shipped their
amp back to us...and all it needed was a simple tube replacement!
you must send back your amp, unplug the power cord, speaker and
reverb cables then remove the chassis from the cabinet by unscrewing
the four mounting bolts on top. The chassis then slides back
like a drawer and comes out. Remove the big power tubes and
mark them according to their location from left to right 1, 2 etc.
They need to be wrapped separately with plenty of wadded up
newspaper around them and put in a smaller box within the larger
carton. To wrap the chassis, use plenty of tightly wadded
up newspaper so there is at least six inches of "crush space" between
the chassis and the cardboard box. Bubble wrap also works
well but please DON'T use styrene peanuts - they will shift during
transit and get lodged inside your electronics as well as allowing
your amp to end up at the bottom of the box unprotected and possibly
damaged. Preamp tubes don't normally wear out as a rule. Therefore,
it is not a good idea to change them just for the sake of changing
them. If there isn't a problem - don't fix it. If there
is no result from your substitutions, it may be possible that you
have more than one problematic tube. Though rare, this does
happen and though it makes the troubleshooting process a little
more intimidating, it is still possible to cure the problem yourself.
It is normal to hear a slight metallic ringing
sound when tapping on the preamp tubes. As long as the tube
does not break into oscillation or start crackling or any other
form of bizzare noise, it is considered normal and functional.
POWER AMPS USED MONO:
Any Boogie power amp
can be used in mono by connecting the input and speaker to one side
only. The input and speaker of the side not in use cannot be
connected or damage may follow. As with any tube amplifier,
a load of some sort must be connected if there is signal at the
input. Always make sure to connect the speaker to the appropriate
side receiving the input signal, and make sure the speakers are
connected to the matching impedance jack on the amp. As an extra
precaution, the volume and presence of the side not in use should
be turned all the way down as well. All current production Boogie
power amps are not bridgeable, but can safely be used in mono under
the above conditions. We suggest alternating sides that will be
used in mono applications to provide even tube wear from side
A to Side B.