On 11/02/2014 10:04, Gareth Magennis wrote:
"Phil Allison" wrote in message
...
Hi,

just put a Marshall JCM2000, DSL100 on the bench.

Looks nice .....

3 output valves installed, 6CA7EH ( Electro-Harmonix, 02/12), only one of
which works.

Two, large mirror burn marks on the glass of one of the dead ones, but the
OT and rest of amp seem OK.

Pulled all the 6CA7s and checked the bias voltage on pin 5 of all 4
sockets = -43V at max setting.

Played hot air onto the PCB near the octal sockets for about 20 seconds
and re-checked.

Pin 5 voltages had dropped to between 28V & 14 V.

Oh **** !!!!!

How did this amp ever survive for this long with such massive PCB leakage
???

The grid feed resistors are all 220kohms too !!!!

Do Marshall actually have spare PCBs for this god awful POS any more ??

What sort of cost delivered to Sydney Australia ?


.... Phil




There is no reason why Marshall would not have these PCB's for sale.
The last one I bought cost me just short of £50 including VAT and carriage.

I guess if you could persuade them to ship to Sydney, the VAT would be
deducted and you would pay VAT/import duty in Australia instead.

They did have a policy of only selling things that might kill people to bone
fide engineers who wouldn't kill themselves or others with High Voltage, so
you might also have to prove you are not a numpty.


If you're really stuck I have one here I could ship you, but with carriage
and import taxes and already paid VAT @20% now, its going to end up bloody
expensive.



Cheers,


Gareth.



Or you could get sculpting on what you have. Possible with small conical
cintride/diamond bits but I now have a set of cintride tile-hole cutters
for a quick neat job.
Explained on a couple of M, on my file
http://www.divdev.fsnet.co.uk/repair2l.htm
IIRC one was thermally-kicked-off conductive pcb problem at a preamp
valve and the other for output valves. Neither have bounced back to me
and one of the owners I'm in regular contact with.
You have to wonder if the replacement M boards are old stock from the
original salt? contaminated board production run