Bad 6v6, no sound, burnt smell - 5f1

Soo...long story short, I may have put a 6v6 in wrong (guide was broken) or it was a compromised tube. Whatever, that's not the story. The story is no sound - obviously - and then burning smell.

The facts: only 30 - 45 seconds on with bad tube.

I replaced bad tube with GOOD tube after, and viola, sound is back; and all good.

Here is the burning smell resistor...Under the main capacitors.

137123

So, you see the burnt board behind the resistor.

Is this ok? Do I need to have someone replace that resistor even though the amp works? The burning smell is going away eventually...

Thanks!!
-Craig

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If it were me I'd replace the resistor and then check the OT

If either were bad, would it be all or nothing? No sound or perfect sound? Or can amps limp along at 50%?

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Well you could just replace the resistor and see

Hard to tell by looking, but that 22K sure looks like a 1/2 watt resistor. I'd change that one also. To a 2 watt.

Hard to tell by looking, but that 22K sure looks like a 1/2 watt resistor. I'd change that one also. To a 2 watt.

It's an import grey 2 watter. Those things will take a stupid amount of heat as we see here...

People like black and white, it's a spectrum...

On one end "If it ain't broke don't fix it!" It certainly ain't as good as new.

On the other end of the spectrum... replace the silly 35 cent resistor although it will cost you five bucks to get one shipped to you.

The OT is probably just fine.

Don't use tubes with missing guide pins.

If either were bad, would it be all or nothing? No sound or perfect sound? Or can amps limp along at 50%?

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I agree witht eh advice above...replace that resistor. IF you wantt o know whether or not the resistor is still doing what it shouldin the circuit, you could measure voltages, right? I wouldn't trust a resistor that has been stressed tas that one has.

AS to the qeustion 'can amps limp along at 50%?".......and amp can limp along at much less than 50%.
I once bought a '59 BAndmaster. This was long before I started doing my own tech work. After the fresh electrolytics were installed, the tech informed me that the OT was producing a whopping 8 watts. AT some point in its life, that OT had been stressed. Flyback voltage probably pierced some insulation on the windings and thereby changed the OT's production radically. It was working...just not as it should have been working.

Limping along at '50%' is not the major concern.

Although unlikely a burnt resistor, rather than rising in resistance value (or failing open) can become a resistor of lower value, or effectively a minimal resistance jumper.

That would be bad. Like destroy another power tube, or even a transformer type bad.

You might even find a suitable replacement at your local Rat Shack.

Don't use tubes with missing guide pins.

Ain't that the truth! Thanks all, as always! I love the wisdom and knowledge!

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Here's Today's Moment of Zen:

That's a screen grid resistor. That's the one that burns in Champs. Doesn't matter what year Champ. I've got a '67 with a big hole burned through the board where that resistor used to be...

Take a look at AA764, '65 and up Champ. That resistor is 1k in AA764, 10k in 5F1. Any value from 1k to 10k will work.

It could be a jumper, sub- optimum but it would work. A jumper isn't a good idea because the rectifier then sees 16uf + 8uf. Still not a bad thing, 5F2A effectively has 32uf for the first filter. AB764 (Vibro Champ) uses 40uf for the first filter.

Alright. I swung it by Jim at Lil Dawg amps and he changed it out for me. He said it was toast. All is good in the cosmos. And, for my conscience, it actually was the tube that failed...not me putting it in wrong!

Closure!

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Well, one can use tubes with broken locator pins if one takes precautions. Sometimes one might have to use one, right? I always mark the base for the location of the locator pin and take care to install the tube correctly. I can't see throwing away a perfecdtly good tube which has only a broken locator pin as a 'problem'. Would I advise a 'rookie' to do this? ONly wiith guidance.

Well, one can use tubes with broken locator pins if one takes precautions. Sometimes one might have to use one, right? I always mark the base for the location of the locator pin and take care to install the tube correctly. I can't see throwing away a perfecdtly good tube which has only a broken locator pin as a 'problem'. Would I advise a 'rookie' to do this? ONly wiith guidance.

If you have a gas stove in your kitchen you can turn the burner way up and sweat the broken base off. It blisters the bakelite but the base with the broken guide pin is junk anyway.

AES sells replacement bases. They turn up NOS every so often. Or you could remove the base from a junk tube, carefully wick the solder from the pins and re-assemble the tube. Yup, I was takin' things apart long before I figured out how to put 'em back together. Stick a blob of 5 minute epoxy in there before installing the new base. Obviously we're talkin' the advanced program here 'cuz if you get it wrong it's still wrong, right? :roll:

If you have a pair of RCA black plates or Xf2 Mullards with one or both pins busted it's worth the effort. How far would you go to save a $250+ pair of tubes?


Murphy's Law revisited:

Parts that can be installed incorrectly will be installed incorrectly.

Parts that can blow up your amp when installed incorrectly will be installed incorrectly and blow up your amp.


Nothing is 100% idiot proof. The universe has an uncanny knack of matchin' unbreakable devices with the dude posessing the ideal skill set to break 'em.