Blew up my Vibro-Champ

[gandhabba]

In the middle of an overdub session yesterday my Champ fizzle pop crackle died. Looked at the tubes while it was in its throes and the power tube (6V6) was glowing blue, then orange then dark and all sorts of weird reactions to the signal coming from the guitar.

I changed preamp (2x12AX7) and power tube day before but not the mystery 4th tube (5YT) as L&M didn't have one. I figure the vibro-champ did NOT like the new tubes (mesa boogie brand made by electro harmonix).

Anyone have any suggestions on what was going on ? Bad tubes ? Should I be getting my $ back ?

[alpep]

5y3 is the rectifier basically they work or don't

when the power tube 6v6 glows it is usually a bias issue.

I bet you blew the grid resister.

unless the tube was shorted when you put it in there. what happens if you put the old power tube back in there?

[gandhabba]

5Y3, yes, thank you.

Well, I put the old RCA 6V6 back in and it works fine again, albeit with fairly reduced power and brightness. It is somewhat microphonic, which is why I replaced it in the first place.

Any way to know if the tube was shorted before I put it in (ie bad tube) ?

[BCR Greg]

Filter capacitors.

The tube obviously needs to go, but your caps are done if your volume is down.

[tafkathundernotes]

5Y3, yes, thank you.

Well, I put the old RCA 6V6 back in and it works fine again, albeit with fairly reduced power and brightness. It is somewhat microphonic, which is why I replaced it in the first place.

Any way to know if the tube was shorted before I put it in (ie bad tube) ?

Usually, a tube glowing orange indicates that it has an internal short. Unfortunately, damage can occur long before any fuse gets around to blowing. Like Greg said, if your power is down, (even with good new tubes), then you probably need a new set of filter caps. The tube going bad like it did is probably not the cause of that condition. Just a factor of time.

The only way to tell if a tube is shorted before plugging it in is to put it on a tube tester. There are a lot of them for sale on e-bay and the prices range widely. Almost all of them will have a basic shorts test. That being said, the tube that blew in your amp would have read fine on the tester then failed later.

[luiss]

I have a microphonic tube somewhere like you on my Mission Amp 5e3 clone,I'll check it and if I find any issue I'll tell you.

You're totally righ this kind of amps don't like new tubes(chinese in particular).I replace some new against old tubes and altough the amp sounded good,it changed for better a lot with NOS old tubes....heaven sound!These little old amps are fantastic!

[Kurt L]

I've got a '65 VibroChamp and all I can say is that it's worth it to have your amp repaired correctly.

I just had a complete cap job, new tubes and it's better than ever. Those are great little amps. One trick ponies, but it's a really good trick.