[Build] CAPI CA-0252, Vintage 2520 Type Opamp, Official Support Thread

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Dumb question - I'm building up four of these, and I noticed that the 2N5087's have three colored stripes on the backs of them, almost like they've been graded. The markings range from what I interpret to mean 415 to 422. I'm guessing this is gain? Does placement matter on these?
 
Dumb question - I'm building up four of these, and I noticed that the 2N5087's have three colored stripes on the backs of them, almost like they've been graded. The markings range from what I interpret to mean 415 to 422. I'm guessing this is gain? Does placement matter on these?
Placement does not matter on the 2N5087s.
 
Hi Jeff!

If I've messed up one of the 2N 5087 transistors, is it okay to replace it with another (not CAPI provided) 2N5087 TO-92 PNP (iPartsLike WXKNewicG-10654) general purpose transistor? Or they don't match that way?

Sorry for the noob question.

Thanks
Mike
 
Hi Jeff!

If I've messed up one of the 2N 5087 transistors, is it okay to replace it with another (not CAPI provided) 2N5087 TO-92 PNP (iPartsLike WXKNewicG-10654) general purpose transistor? Or they don't match that way?

Sorry for the noob question.

Thanks
Mike
That should be fine.
 
Curious why the ca-0252 use what appear to be carbon film resistors. No complaint, they sound great, but just wanting to understand more. Why were carbon film chosen for the op-amp, whereas the main board uses mostly metal film. Thanks!
 
The OG that I took apart was all carbon film. I don't know if they had a "standard" back then or used what they had on hand or could get at that moment in time. Either way, Joel and I did some experimenting and thought the carbon was sonically closer to the OG than metal film so off we went.
 
Hello, I just finished one and realized, that the terminal pins are ridiculously long, is this correct like this:


Foto 05.01.23, 01 45 05.jpg


Foto 05.01.23, 01 45 17.jpg


I can't push them down any more. Should I clip them?


Thanks and greetings from Vienna, Austria!
 
Hello, I just finished one and realized, that the terminal pins are ridiculously long, is this correct like this:

I can't push them down any more. Should I clip them?

Thanks and greetings from Vienna, Austria!
No need to clip them. They have the same clearance as the modern 2520. That way they can be used in all of the same modules.
 
Thank you! I was concerned because all the older builds look like the opamp is nearer to the board. Gotcha thanks!

Were the rings on the pins soldered to the top of the board, or the bottom? The pins will be even longer than expected if soldered to the bottom. Ask how I know... :)
 
Forgive my ignorance, just trying to cover all bases...is there a reason why the CA-0252 only has 5 pins? The pcb's i've seen seem to have slots for 6 sockets. Again, sorry if i'm missing something here really basic. I know it's not the same DOA as the Gar2520.
Much thanks!
R
 
Forgive my ignorance, just trying to cover all bases...is there a reason why the CA-0252 only has 5 pins? The pcb's i've seen seem to have slots for 6 sockets. Again, sorry if i'm missing something here really basic. I know it's not the same DOA as the Gar2520.
Much thanks!
R
The original 2520 had no internal circuit connection to ground. Many of the more modern amps have added onboard 0.1µF PSU decoupling caps which of course go to ground. Since the original amp did not have these, I did not use them either. Hence, why put in a pin that literally connects to nothing :)
 
Ok, thanks so much! Looking forward to getting started on this. First foray into building in this vein. I've built a couple of tube guitar amps and pedals but nothing like this so everything is research research etc. right now lol
🎤😊
 
The original 2520 had a small piece of thin single sided copper clad board covering the solder connections, which acted as a shield (of sorts) for hum and rf.
This was connected to the 0v pin.
 

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