One tube glowing brighter [Archive]

TechpriesT

02-26-2006, 09:49 PM

Hey, my friend has an amp and one tube is glowing brighter then the others. Is there something wrong?

brad347

02-26-2006, 10:29 PM

let me guess, new production tubes? I think that can be normal with new production tubes.

mbratch

02-27-2006, 05:35 AM

How much brighter? Are they the same kind of tubes in the same area (e.g., all 12AX7 preamp, or all EL84 power amp)?

Blue Strat

02-27-2006, 08:08 AM

Hey, my friend has an amp and one tube is glowing brighter then the others. Is there something wrong?

Not if the amp is working. If they're 2 different brands or models (of the same brand) this is not unusual. Even the same exact brand/models can glow differently.

mbratch

02-27-2006, 08:29 AM

I recently fixed a problem in one of my amps where one of the EL84's was glowing brighter. Turned out one of the pins wasn't getting the voltage it was supposed to (it was an open connection on the PCB). Hardly noticed it from the sound of the amp, maybe a slight loss in preceived output power.

Blue Strat

02-27-2006, 10:11 AM

I recently fixed a problem in one of my amps where one of the EL84's was glowing brighter. Turned out one of the pins wasn't getting the voltage it was supposed to (it was an open connection on the PCB). Hardly noticed it from the sound of the amp, maybe a slight loss in preceived output power.

That was probably the plates glowing, as opposed to the heater, due to lack of bias.