"Phil Allison" wrote in message
...

** Hi,

I have a VOX AC100cp ( Chines made) on the bench - it is about 6 years
old. It has all its original parts but is in a very bad way. The known
faults a

1. One (Ruby) EL34 has lost vacuum.

2. Two scorched 5W screen resistors, one detached from the PCB.

3. One blown HT fuse, a 1 amp slow blow - which may well not be the only
one.

4. Output tranny OPEN on one side of the primary and exhibiting symptoms
of shorted turns.

5. Bridge rectifier only conducting on one half cycle - giving 50Hz
ripple.

The scorched 5W resistors are on the side with the open tranny winding.

The EL34 with no vacuum is on the other side.

Wanna have a go at the sequence of failures ?



... Phil



Well my uneducated guess is that it had to have started with the tube with
the lost vacuum.
Don't know what the normal subsequent failuire mode is, but I suspect either
the tube would short Anode to ground via heater cirduit perhaps, or would
just send the bias way off the planet.
Huge DC through the OPT primary partly via the scorched grid resistors on
the other side, and a nasty expensive smell.
Poo.



Gareth.