Very low volume, farty overdrive. Blown transformer?

[Triocd]

Hi everyone,

I bought a late 50's/early 60's Gibson Gibsonette. When I received the amp unfortunately it is barely above conversation volume and the overdrive is really farty. I can return the amp for a full refund, but I got a pretty good deal on it and was planning on sending it in to be updated anyway. I want to keep it and fix it but I'm worried that if I keep it I'll find out I have a blown transformer. If it does have a bigger issue like that, I'm better off sending it back and waiting for a better one to come along.

What are the odds it's a blown power or output transformer and are there any things I can do or look for to rule that out? I replaced all the tubes and I thought that would be the trick, but that didn't help. I haven't changed the speaker to test that because I haven't had time, but it looks fine. My gut tells me it is a simple fix like a faulty resistor or a bad solder, but I want to throw it out there for any opinions.

I don't have the ability to poke around the chassis and check voltages etc.
Thanks!

[Leo_Gnardo]

Gibsonettes are much like Champs: you get 4 or 5 watts of "clean" power, above 400-500 Hz. The power figure drops steeply as you apply lower frequencies, so the low notes on a guitar easily get into farty territory. If I'm not mistook, there's also an interstage transformer that feeds the output tube. I've had a couple cases where that transformer was bad and needed replacement. Antique has a part that will do, about $20.

[J M Fahey]

I don't have the ability to poke around the chassis and check voltages etc.
Thanks!

Sorry but if so, send it back.
We will willingly help you, but only through suggestions, the actual hands on side is on you.

[Sowhat]

I doubt that you have a blown transformer but anythings possible. It would be a good bet that all the capacitors in the thing are well beyond their drink by date and should be replaced, they're probably leaking like sives, that plus some pot, jack and switch cleaning is all it probably needs.

Of course if you're not the poking around type of guy then you need to bring it to your local amp tech.

[Mick Bailey]

There are simple checks, but simple is a relative term. Output transformers are at the bottom of the list of failures, but they do happen. R.G.'s 'Neon Trick' is a simple check, but you still need to open up the amp and poke around - and observe all the safety caveats. If you intend to bring this amp up to date as a 'player' then it will need a thorough overhaul, but any amp from that era will, unless you buy one that's had a re-cap and the grounding sorting out if it has a 2-wire mains cable.

Similar story here;
http://music-electronics-forum.com/t34776/

[Sowhat]

It would be a good bet that all the capacitors in the thing are well beyond their drink by date and should be replaced, they're probably leaking like sives,

Strange me posting to my own post but I omitted an interesting thought about this... This amp is around 60 years old, it may have been recapped in 1970 and then again in 1990 and now that it's 2017 it probably needs to be recapped again. Caps have a limited lifetime and even though you may inspect the chassis and find that newer caps have been installed, this does not mean that they are still O.K.

[Triocd]

Strange me posting to my own post but I omitted an interesting thought about this... This amp is around 60 years old, it may have been recapped in 1970 and then again in 1990 and now that it's 2017 it probably needs to be recapped again. Caps have a limited lifetime and even though you may inspect the chassis and find that newer caps have been installed, this does not mean that they are still O.K.

Thanks for the ideas everyone!