Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: ebulakowski on September 15, 2020, 08:54:40 pm

Title: 1952 fender champ 600 repair/resto question
Post by: ebulakowski on September 15, 2020, 08:54:40 pm: Hello forum world!
I recently picked up a 1952 champion 600. Leaky caps, a 2 prong extended with a twist and electrical tape... needless to say it was time for some love.
But here’s where I’m seeking some advice. It’s up and running and I left almost all components stock. But some of the resistors (specifically the bias resistor) have wandered. It’s at about 750ohm instead of 500. So my 6v6 is running at about 55-60%. I’m leaning towards replacing it. I just figured I’d ask the amp worlds opinion since aside from the electros and one cap, it was all stock. Do I run any risk getting that 6v6 to appropriate output? I know this early model has a pretty sMall OT.

I’ve attached a pic of the schematic with drifted values written in. Any thoughts are welcome. Thanks!!!
Title: Re: 1952 fender champ 600 repair/resto question
Post by: tubeswell on September 15, 2020, 09:48:54 pm: If you put a 470R to 500R cathode resistor in for the 6V6, it will run nicely.
Title: Re: 1952 fender champ 600 repair/resto question
Post by: PRR on September 15, 2020, 10:37:23 pm: > about 55-60%

I assume you did not buy a stock 1952 Champ to fill Wembley Stadium (https://www.wembleystadium.com/about/press/stadium-facts-and-features); even if you did, another watt or two won't make the stadium run over. And half power is not half loudness.

However, a composition resistor, rated 1/2W, running at 0.45W, drifted from 500 to 750, is liable to drift to infinity. Use at least a 1W part. I would go 2W. There's a similar resistor in the B+ which is also adrift.
Title: Re: 1952 fender champ 600 repair/resto question
Post by: Latole on September 16, 2020, 02:51:29 am: Replace all 3 filter caps by high quality one like F & T. 10 mfd will do the job
The one in the center leak
Keep all the old parts in a safe place for the nex owner or collector

Filter caps ; Twin 8 mfd cap
https://www.tubesandmore.com/products/capacitor-ft-450v-88-f-axial-lead-electrolytic

single 10mfd cap:
https://www.tubesandmore.com/products/capacitor-ft-500v-type-axial-lead
Title: Re: 1952 fender champ 600 repair/resto question
Post by: ebulakowski on September 16, 2020, 08:51:14 am: Thanks for chiming in. Latole, yes all the cap work has been done already. That was a before pic.

PRR great point, I should save someone else the headache and address the drift issue before it keeps going... and going.... and awww crap!

Thanks guys
Title: Re: 1952 fender champ 600 repair/resto question
Post by: Latole on September 16, 2020, 09:21:43 am: What caps brand did you put ?
Title: Re: 1952 fender champ 600 repair/resto question
Post by: ebulakowski on September 16, 2020, 12:19:53 pm: I had some spragues on hand.

Quote from: Latole on September 16, 2020, 09:21:43 am
What caps brand did you put ?
Title: Re: 1952 fender champ 600 repair/resto question
Post by: Latole on September 16, 2020, 12:22:25 pm: Quote from: ebulakowski on September 16, 2020, 12:19:53 pm
I had some spragues on hand.

Quote from: Latole on September 16, 2020, 09:21:43 am
What caps brand did you put ?

Great, Sprague or F & T are the caps I'ill put a good American made vintage amp !