Marshall jcm 2000 Dsl 100 problem red plating out put tube need help!!!!!

[vphathom]

my amp is 3 years old only 10-12 hours use
it quit while I was playing and one of my out put tubes was redplating
so I took it apart and found a burned resister R6 1ohm 1watt it ties pin 7 and pin 1 el34
I dont now if thats the only problrem ?? the rest of the pc board looks good
any ideas???
I have ordered a new resister and I will put it in, but
I dont know if the resister caused the tube to red plate, or the tube caused the resister to blow ?????
whin i get the resister in is there any test i can do before, I risk new tubes and burn them up
can the bias resisters cause this, they look good but I have not pulled them out to test as of yet

[Enzo]

The schematic has an error. The resistor and pin 1 connect to pin 8, not pin 7. The heater in each tube is between pin 2 and pin 7 not pins 2 and 6.

That resistor burns out when tubes fail. It has no way to damage a tube itself.

[vphathom]

thanks for the info
what brand of tubes do you recomend I was on the tube dr. web sight, and aplified parts web sight there are alot of el-34's to chose from.

[Enzo]

I have no specific recommendation, perhaps someone else does.


I have got good service in recent years from Ruby EL34B, no one has come back and complained about them,and I have not had any failures. I can't afford WInged C ones, but I do like their sound. Others often like the EH and other brands.

[vphathom]

the amp is fiXed I replaced R6 (1ohm 1WATT resister and replace the tubes with Ruby EL34B'S AND JJ PREAMP TUBES AND IT SOUNDS GREAT CLEAR AND CRISP the over drive is real clear not muddy
just got the parts today
thank you

[g1]

Here's the factory bias info if you need: