to change tubes
so your organ or guitar tube preamp or amplifier is sounding like a sick dog in
the middle of the night and you want to fix it without spending a lot of money,
changing the tubes can make a major difference and get your favorite amplifier or
organ back to sounding like it should so you can impress all your friends with
that great vintage tube sound.
how do you know when to change the tubes and which ones to change? Here are
some suggestions that have been helpful to others over the years
that you may have a tube problem:
1. Your amp/preamp is
DEAD! – no sound at all and the tubes are not glowing. Check that your power
cord is plugged in and your amp is turned on and the fuse is good. All tubes
don’t go out at once unless they all have no power.
2. You have sudden
changes in output levels, loss of highs or perhaps mushy lows or muddy chords
and some notes may sound weird, you have poor or no balance between notes or
the amp makes “funny” noises like popping or crackling.
3. Your power tubes (the
big ones) may become microphonic and sound like a big echo or a torn speaker.
This can also happen to preamp tubes like the 12AU7 or 12AX7 when they go bad,
but usually the output gets low if the preamp tubes are deteriorating.
4. The power output
(sound level) isn’t as high as it used to be because you have to turn the
volume up higher to get the same level of output. The cause is simple, output
tubes deteriorate gradually over time along with a loss in both bass and treble
5. You have a tube that
is not glowing or lit up but others are ok. This usually means one has
prematurely burned out and the rest will shortly follow – better to get a whole
new set and keep the old ones as backup (throw the bad ones away – recycle them
as glass please!)
6. Remember bad tubes
can cause premature failure of other parts, such as the output transformer,
speaker, and other vital components and these may already be bad if you didn’t
change the tubes in time or regularly.
you have some of the symptom described, now what do you do?
musicians should change their tubes once a year if they play moderately loud
and fairly often (like church organs or concerts). For Hammond organ players
the power tubes in the tone cabinets often get very hot and lose power over
time. You should also remember to check the tubes in the organ console as they
are often the preamplifier which feeds the signal to the tone cabinet
amplifier. Sometimes there is a separate reverb or vibrato amplifier or power amplifier
(Like Hammond A-100, D-100, L-100, and M-100 series) in the tone cabinet (or
console) and you will need to change these tubes also if you sense or hear a
problem like I mentioned above.
the old days, you could take out your tubes (mark which holes they came from)
and take them down to the corner drugstore ands test them. Unfortunately tube
testers are no longer conveniently available to do this and the test only lit
up the tube and rarely tested it to the same conditions as in your amplifier with
the correct voltage and bias conditions. So even if the tube was “OK” on the
tester it still may be weak in your amplifier. So testing your own tubes is
not a convenient option.
most reliable alternative is tube- for-tube replacement and a before-and-after
comparison. You can do this one tube at a time (like changing spark plugs one
at a time) until your amp sounds better or just replace them all at once
(easiest) and start to enjoy the great sound your amp put out when it was new
you do replace the tubes (and most people can do this), remember to turn off
the amplifier (or organ console and tone cabinet), unplug the cord, let the
tubes cool down if they were turned on and replace one tube at a time with the
new tube (remove the old tube and put in the new tube and go to the next one,
TAKE OUT ALL THE TUBES AND PUT THE NEW ONES IN WITHOUT MARKING THE HOLES THEY
CAME FROM! Many tubes have the same pin configuration and will fit in several
places they are not electrically compatible and may cause a major problem. But
if you are careful this won’t be a problem and you amp will be happy with its
new tubes and so will you!
luck and may all your notes bring happiness to their listeners!
out my eBay store for tubes for many guitar amps and most Hammond consoles and
tone cabinets from Hammond and Leslie and many Ham Radio/Linear amp tubes.