THE FOLLOWING ARE INTENDED FOR GENERAL KNOWLEDGE ONLY. ALWAYS UNPLUG ANYTHING BEFORE YOU TAKE IT APART.
ELECTROCUTION IS NOT FUN AND SERIOUS INJURY CAN OCCUR, SO PLEASE USE YOUR HEAD!
FUSES: Should only be changed out with a like type and size. Never replace a
blown fuse with a larger value fuse (this will only cause more damage to the unit in question).
In some rare instances a fuse will blow for no apparent reason. However, most of the time if a
fuse blows there is a reason for it. If it is in an amp, check your speaker cables, check the
speaker, make sure you are plugged into good power, some clubs have awful wiring and can create
problems for the performer. If you have checked everything else out and you are still blowing
fuses take your amp to a qualified technician.
POTS: (volume controls, tone controls, etc.) - If your amp, mixer etc. is cutting out
and/or sounding scratchy, try cleaning the pots. An easy way to do this is turn your unit off,
then turn the pot fully clockwise then counterclockwise. Do this several times and at a high
rate of speed. Now turn the amp back on and try it. Did the scratchy sound go away? If not you
can use a cleaner such as "De-Ox It". Here are some basic guidelines for doing just that:
- Never spray out a fader (like on the eq section on a powered mixer or the main
channel control on a mixing console) with a cleaning agent. This will cause the fader
in question to lose its feel and to have a "sticky" feel. A regular radial pot will
lose its feel as well; however, it is much more noticeable in an in-line fader.
- Once you get to the part in question locate an opening in its covering (usually
right where the legs come out). Some pots do not have an opening and should be replaced.
Be careful of over spray. You do not want to saturate the circuit board with a cleaning
agent. This may cause the unit to short out and may cause permanent damage.
If this still does not cure your problem you either need to replace the part or there is
something else wrong.
If you know how to solder, and feel that you are
inclined enough to get the unit apart without breaking anything. (Don't
kid yourself here! I've seen lots of circuit boards damaged by people
who tried to fix it themselves.) Check for bad connections where the pot
connects to the circuit board.
THE THREE PRONGED CORD.
Many old timers know what it feels like to get electrocuted by their guitar
amp. We all remember the story about how Keith Relf was killed
by his guitar. Here's why that probably happened. old guitar amps were
not chassis grounded. The cord had a two pronged plug and in the example
I'm going to use, a blackface fender super reverb, there was a switch
for the ground polarity. Simply put if you flipped the switch one way
then one of the prongs was connected to the chassis. If you flipped it
the other way then the other prong was connected to the chassis. Since
the vast majority of guitar players don't carry a multimeter it was
anybody's guess as to which way was correct. Get it wrong and you may have
never known. Todays pa equipment however is grounded. So if you guess
wrong you will not know....until your lips touch a microphone.
Imagine 120 volts AC conducting though your teeth!!!!
To correct this and make the amp safe we install a three pronged
chord. Done correctly this brings the amp up to modern safety standards
and guarantee that you are not a victim. In the First picture below is
a super reverb that was brought to my shop after somebody else had
replaced the cord. Unfortunately it was done wrong. I will give the guy
credit he only did it partially wrong. He did connect the green wire
(the earth ground) to the chassis). This is exactly what you want to do.
But he messed up on the fuse. In the first example the fuse is on the
white (neutral) wire. This is wrong because if the fuse blows one of two
things can happen. Either A: the amp will conduct through the chassis
making the blown fuse useless. Or B: the amp will conduct through you!!
Incorrect. (1)The white wire comes in and is connected to the
accessory socket
(2) it goes from there to the ground polarity switch
(3) then it goes off to the fuse.
Correct. (1) the black wire comes in and goes to the
accessory socket
(2)
Then it goes to the fuse holder
(3)
it leaves the fuse holder and goes to 4
(4) it leave the switch and goes to the transformer
Notice that the white (neutral) wire comes into the chassis goes to
the ground switch then straight to the transformer.
There is nothing wrong with doing this yourself but PLEASE DO IT
RIGHT!
NEVER EVER UNDER ANY CIRCUMSTANCES GLUE A KNOB TO A POT!!!!! If you have a knob that is loose
and wants to fall off of your unit simply wrap a piece of Teflon tape or paper over the shaft
and slide the knob overtop of it. If you glue your knobs on they cannot be removed and future
service is not possible without destroying the pot. At aprox $5 a pot that can add up quick.
