Fender Super Twin Reverb distortion circuit

[Randall]

A 1979 Super Twin came in from a music store storage that has not been turned on in decades. All the tubes were missing, except (luckily) the two expensive odball tubes. One of those is a 12 pin compactron. I got it all working except for the distortion circuit. It worked for a short time, but it sounded horrible, raspy and thin. It does not work now. The customer in this case does not want to spend the money to recap it, since he believes it isn't worth more than about $500.

My inclination is that if he won't replace the 40+ year old caps, I don't think I want to dig in any deeper in case this is cap related. I did fix one of the parametric filters by finding an eyelet that had never been soldered.

I don't really understand this distortion circuit. I am puzzled by what is going on around 6C10 A and C. Maybe someone can explain how this is supposed to work?

https://www.thetubestore.com/lib/the...-Schematic.pdf

[The Dude]

No offense, not helpful, apologies, and not meant to derail.

I never bothered to analyze that circuit because it sounds like ass.

Edit: "it sounded horrible, raspy and thin" It was working exactly as designed.

[J M Fahey]

Same here.

As of "not recapping because itīs not worth more than $500" , WHEN (not IF) it fails because of that it will be worth nothing.

And for $500 he can buy another ... which will STILL need recapping.

[Chuck H]

Same here.

As of "not recapping because itīs not worth more than $500" , WHEN (not IF) it fails because of that it will be worth nothing.

And for $500 he can buy another ... which will STILL need recapping.

That is so perfectly accurate and logical that no guitar player would ever agree.

[The Dude]

On the other hand, you could take your 500 bucks and buy an amp that sounds better.

[Chuck H]

On the other hand, you could take your 500 bucks and buy an amp that sounds better.

Ah! But like Juan said, you have to maintain your investment to make that happen. Alas... The crustomer is a guitar player.


(As many of us are, obviously. But there's a difference)

[Jazz P Bass]

Sheesh.
Not being much help for the poor guy.
He stated that it 'worked' & now it doesn't.
Randall, what have you tested so far?

[Randall]

This is a tricky one. He got it for about $200 recently. But when he found out it needed 6 power tubes, and 4 or 5 preamp tubes, plus I recommended re-capping it, he paled at the price. He just wanted to get it up and running at the least cost, so since none of the caps had exploded yet, I went that route. I got everything working, except for the distorto circuit. I had him at a very reasonable price with good used tubes, but he then inquired about how much of a pain would it be to get the distorto working? I told him by all accounts it was not a good sounding circuit, and would probably put him over his cost restrictions to delve into it. Plus, it is a act of congress to get the chassis in and out of the cab, and I voted to just let it be.

So, I did not measure anything in that circuit. I didn't see how the darn thing was supposed to work in the first place. I buttoned it back up, it is working except for the distorto circuit, which I doubt anyone ever would use anyway. He got his albatross back working for less than $200, and I have washed my hands of this situation. It is what it is.

I still would like to know how this was designed to work, but if that doesn't happen It's all good. I'm on to the next thing.