6 Jun
2015
6 Jun
'15
10:51 a.m.
On Sat, 06 Jun 2015 06:15:04 +0200, Robert Edge wrote:
One side of the power line coming in to the amp is
tied to the chassis
through a capacitor, the ground switch changes which one. This is what
is known as the 'death cap' in amp-dude circles.
When it dries out and fails (not if, when), the chassis will be hot
when the switch is in one position.
I didn't know that, but indeed, in a book [1] I see an old Fender:
ac switch
~ o──┬─o/ o──────────────)│(
│ )│(
o ground switch )│
\o────┐ )│(
o ┴ C 50n )│(
│ ┬ 600V )│(
│ ┴ )│(
│ ground )│
│ )│(
~ o──┴────────[fuse]─────)│( The audio IOs are connected to ground, so
guitar strings would be hot too, if the
capacitor has got a short.
[1] "Röhren-Verstärker reparieren, restaurieren, modifizieren", Rainer
zur Lind, ISBN 3-89576-028-5