Flash Upon Power Up

[HJW]

On my tube amp, when I turn the power on, I see an orange flash under one of the power tubes. Is this common ?

[HJW]

Anyone ?

[stokes]

Do you mean the main power switch,or the standby switch?When you say "under the power tube" are you refering to a flash between the tube base and the tube socket,or just inside the bottom of the envelope?

[HJW]

Do you mean the main power switch,or the standby switch?When you say "under the power tube" are you refering to a flash between the tube base and the tube socket,or just inside the bottom of the envelope?

Main power switch. Amp on standby, as proper. I just tried it again, and didn't notice it, but my room is well lit right now. Both times I've noticed it it was night with dim lighting. The flash is brief and not too bright, but it's coming from under/inside the power amp chassis.

The chassis does not sit flush against the bottom of the cabinet, and what I'm seeing is probably the reflection off the shielding on the inside of the back of the cab. Also, after looking at the chassis photo again, the light may be coming out of the hole on the side of the chassis.

[HJW]

I'll add that I see no flash inside the tubes themselves when turning the main power switch on. They simply begin glowing.

[dai h.]

if it's the turn on flash of the heaters, it's normal for some tubes to do this and nothing to worry about. This info should already be out there though if you search the archives or google.

[HJW]

if it's the turn on flash of the heaters, it's normal for some tubes to do this and nothing to worry about. This info should already be out there though if you search the archives or google.

Ok, It's not an alarmingly bright flash. It's just my first tube amp, and I thought I'd see if it was normal. That's the info I was looking for though, and I appreciate your taking time to offer it. Thank you.

[Bruce / Mission Amps]

I really believe it is not normal to see any flashes anywhere like this.
It is normal to see some old 12AX7's filaments glow very brightly momentarily when first powered up but any fast glowing filament/heaters or flashes not in a glass envelope is trouble.
Something is amiss but it could be as simple as some small filament of a stranded wire touching somewhere around a tube socket or even some conductive carbon scoring, dirt/lint, etc.
I'd be careful about it and pull the chassis, flip it over so you can see inside the chassis and watch what happens when you plug the amp in with the power and standby switch in the play mode.

[HJW]

I really believe it is not normal to see any flashes anywhere like this.
It is normal to see some old 12AX7's filaments glow very brightly momentarily when first powered up but any fast glowing filament/heaters or flashes not in a glass envelope is trouble.
Something is amiss but it could be as simple as some small filament of a stranded wire touching somewhere around a tube socket or even some conductive carbon scoring, dirt/lint, etc.
I'd be careful about it and pull the chassis, flip it over so you can see inside the chassis and watch what happens when you plug the amp in with the power and standby switch in the play mode.

Ok, I just took a closer look now that it's dark. I was wrong, it is in the envelope. Pardon my lack of terminology Actually, the shielding is what made me think it was coming from below. It was reflecting it and making it look like a problem. I live I learn.

Thanks for taking time to clarify.

[dai h.]

that's good because I wasn't looking very closely at the first post either (as I should have been). Glad it wasn't anything serious.