| * J = Jack, P = Pot,
F = Filter cap * Do not try and
solder wires to the chassis itself. A ground that is soldered to a chassis
is not as good as a soldered and bolted down ring terminal ground.
* Do not do STAR grounding. I have removed
many star grounds in amps to fix grounding problems.
* Do not use the brass Fender style
grounding plates. These plates corrode eventually and do not make good
contact between the chassis and the brass.
* The power transformer bolt ground wires
have a round ring terminal crimped and soldered to them. They can then be
bolted down firmly to the metal chassis.
* The Marshall style pot buss wire is shown
above. This is a bare wire that is soldered to the back of every pot and is
connected to the input jacks ground lugs. I recommend using this buss wire
system. You may have to grind, sand or file some of the coating off of the
back of the pot so that you can solder the buss wire to it. A 40 watt iron
minimum is usually what it takes to solder this buss wire to the pots.
* Make sure all Jacks and pots are bolted
down firmly to the metal chassis. If you use plastic jacks, make sure all
jacks are grounded to the pot buss wire.
* Your circuit board may have multiple
grounds leaving the circuit board. Pre amp grounds are soldered to the pot
buss wire. Bias supplies, rectifiers or power tube cathode ground wires all
go to the main power transformer bolt.
* All power transformer Center taps get
bolted down to the main Power transformer bolt.
* If you use two 100 ohm resistors as your
heater center tap, do not use the power transformer heater center tap wire
and visa versa.
* If you have a reverb transformer, make
sure the reverb jacks are bolted to the chassis and the reverb transformer
ground wire is soldered to a ground lug on the reverb jacks. Do not use
insulating washers on the reverb jacks.
* Speakers jacks are bolted firmly to the
metal chassis. The output transformer ground wire is soldered to a speaker
jack ground lug. If you use plastic speakers jacks, solder a ground wire to
the jacks and bolt it down to the main power transformer ground bolt where
all the other grounds are bolted.
* Your power tube cathode wires may be on
the circuit board or leave the tube sockets and go right to the main power
transformer ground bolt.
* The power cord green wire can be bolted
down to the closest power transformer bolt.
* Filter cap notes: #1 is your main filter
cap(s) that are connected to the rectifier. #2 are the power tube screen
grid filter cap(s). These two filter cap stages both get bolted to the main
power transformer ground bolt.
#3 are all the pre amp and phase inverter filter caps. They are all soldered
to the buss wire that runs down the back of the pots.
* If you have a separate rectifier board or
a bias circuit board or a Bridge rectifier bolted down somewhere, all these
grounds should get bolted down to the main power transformer ground bolt. |