Bias problem- 1 Socket shows extremely low bias!

[kevinkr]

Originally posted by HollowState
You haven't mentioned what "type" of resistor(s) burned. If they were film resistors these have very little tolerance for overloads, even momentary. Film resistors act like fuses when overloaded. Especially metal film types. That's why they're call flameproof resistors. For screen resistors this is a good place for carbon composition types like Allen Bradley. They can smoke and still continue to function. If you're burning out 5 watt wire wounds, then it's probably a result of todays imported garbage tubes.

Just to dispel a misconception in the previous post, not all metal oxide or metal film resistors are flameproof. You must purchase ones that are specifically specified as being flame proof.. I have seen more than a couple of metal film types burn, although I have yet to see any metal oxide types burn IIRC...

Carbon composition and carbon film types burn like crazy, (direct personal experience - BIG, SMOKY FIRE!) while the CC types are very overload tolerant the CF types are not. I would not use them in any application where there is a possibility of an overload situation that could result in extended overheating. In such a case I would use a flameproof fusible resistor. (Digikey, Mouser, etc.)

[otokomae]

It was a 1 watt, 470 ohm metal film resistor. There were no flames, but it did turn dark brown and leave a brown burn spot in the PCB. My only guess is that it must've been a bad tube; I had just changed to a new set of tubes before the problems started, so I'll have them checked. Does moving up to a 5 watt resistor help at all, btw?
Thanks!

[kevinkr]

Using a 5W resistor should reduce the incidence of this sort of failure - no reason not to imo..