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STA15 component layout diagram

Mike P

Mike P

Trade: Pickwell Audio
I'm just about to start some work on an STA15. Does anyone here have a diagram showing the component layout/locations they could share?

Thanks!
 
A new one but it's the same:

DSC_1746-copy.jpg
 
It's a series 3 that I'm working on.

So far I've discovered that R19 and R20 are 390R on both channels and not 470R and that R32 has drifted up to c75K.
 
Now isn't that strange, R32 was the resistor that had wandered the most on my STA15 too, to 74.8K (left) and 76.4K (right). I replaced R19/20 with 470R from the 390R originally fitted.
 
I upped my cathode resistors from 390R back to 470R to reduce strain on the EL34s. Presumably Radford went the other way back in the day when Mullards were freely available.
 
chiily said:
Will, is there a conscious decision why the the film bypass caps aren't fitted on this one? I'm just curious....
Click to expand...

I stopped populating them years ago - these boards are 1:1 copies of the Woodside STA15/25 replacement boards which have provisions for them.

Basically an electrolytic has a far lower ESR than a 33k / 39k anode resistor!

Mike P said:
It's a series 3 that I'm working on.

So far I've discovered that R19 and R20 are 390R on both channels and not 470R and that R32 has drifted up to c75K.
Click to expand...

390R is correct, I just fit 470R to run things a little cooler.
 
Will, how much is a pair of populated replacement STA15 boards? The boards on this amp are quite scorched with a couple of lifting traces.
 
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