No Sound, Blue Glow... How'd this happen?!?

[otokomae]

OK, I have a Fender Supersonic that has gone from working fine to freaking out in mere minutes, and I can't find the cause!

All I did was change the tubes, set the bias for the new tubes, and when I put it back together there was no sound! Also, the tubes have started glowing blue, and I noticed that the jewel light, which used to come on dim and sort of go "in and out" while playing, is now on FULL and BRIGHT from the moment I switch the power on! I've tried changing to other, confirmed working power tubes, changed out the PI driver, and have the chassis open now, looking all through it for anything that might have burned out, but I can't find anything!

Can anyone offer me any help here, or possibly give me any idea where to start looking?

Thanks in advance!

[Phil_S]

Blue glow is normal on some tubes. It looks cool in the dark and generally isn't something to be concerned about.

I'm thinking you disturbed an already failing solder joint somewhere in the filament string (pilot light problems) or maybe elsewhere? Maybe tubes just aren't fully seated in the sockets? It's hard to know.

A good visual inspection (with magnifying glass) of the cold chassis is in order first. Then on a hot chassis (out of the cabinet), with speaker attached, and a chopstick in hand to probe for the problem. The other hand belongs in your pocket. Don't do this unless you are familiar with safety precautions on high voltage equipment.

Maybe it's tech time?

[otokomae]

Yeah, that's along the lines of what I was thinking, actually... I guess I was just hoping that there might be some simpler solution that I wasn't thinking of. The solder joints on PIN 7 of tube V7 and PIN 2 of each of the power tubes in particular are a little "brown"... any ideas about which tubes/pins would be most likely to cause this problem?

[Cygnus X1]

Odd problem I noticed on a recent amp build...

The light was flickering, I noticed it and thought nothing of it, until the amp "ate" a preamp tube, burned out a preamp cathode resistor, and then started to burn up a B+2 resistor. I thought my calculations were off.

It turned out that the bulb was causing a filament (heater) current drop.

I knew that it wasn't due to a skimpy current supply, that was the first thing I checked. I replaced the bulb, and things are fine with it now.

[otokomae]

Weird..... now that's something I probably wouldn't have thought of!
I'm gonna have to check the bulb now! Thanks!!!