Power Screen Grid Resistor

[Ryteone]

I'm working on a Carvin Legacy I combo amp.  One of the power tubes failed and smoked the screen grid resistor (lucky just fired it and didn't explode, had the little 100 ohm resistors in the heater circuit vaporize and fuse to the circuit tracing).  Carvin is using 350 ohm 5 watt screen grid resistors (I'm guessing for starters because of the switch to allow you to substitute the EL-34's for 6L6's).  Currently I've got 330, 470 and 1K ohm in the 5 watt range.  I wanted to see what the general consensus is with the guys on here that really repair amps and not just hack around like I do.  I was thinking of using the 470 and replace the other three with the same value.  Does that seem to be the best choice?  I've attached the schematic just incase.


Scott...

[sluckey]

I see 1K/5W in a lot of EL34 circuits.

That vaporized 100Ω in the filament circuit is a good indicator that one of the EL34s has had a short between pin 2 and 3. I'd examine the output tube sockets to be sure there is no arced carbon track between those pins.

[Ryteone]

That's what I'm used to seeing with the EL-34 circuits, just thought maybe since it is circuited to run with 6L6's also that's why they would have it lower.  The tube had gone all powder white inside.  I guess it had been making a humming/growling sound with a decrease in volume.  Would of been nice to catch it and just change tubes before it failed.  I was going to ask if they don't plan on running any 6L6 tubes I'll go with the 1K, have about 30 of those new left.


Thanks Scott...

[sluckey]

A lot of people think that using a 1K/5W on 6L6s or even 6V6s is an upgrade. If I was gonna be running different tubes in an amp I'd use 1K/5W.