shabtek
Well-known member
custom manufactured transistors!???
[Build] CAPI CA-0252, Vintage 2520 Type Opamp, Official Support Thread
- Thread starter jsteiger
- Start date
Help Support GroupDIY Audio Forum:
Believe it or not, yeah. Were currently waiting on many other customs for our ADM202 and 1731 amps. TIS92, TIS93, 2N3704, 2N4062, 2N5376, 2N5086, 2N3053 and 2N4037. Woohoo!
klem
Well-known member
This question relates to both 0252 and VP28, I'll post wherever you prefer...
I built 16 0252s for 8 VP28s. 15 work great, but the last one, when placed in fader booster position, R17 on the op-amp and PR 2-4 on the VP28 smoked - see pics! Besides replacing these 3 R and checking for shorts anywhere obvious, anything else you recommend replacing or measuring before trying it out again? Diodes? Thanks,
I built 16 0252s for 8 VP28s. 15 work great, but the last one, when placed in fader booster position, R17 on the op-amp and PR 2-4 on the VP28 smoked - see pics! Besides replacing these 3 R and checking for shorts anywhere obvious, anything else you recommend replacing or measuring before trying it out again? Diodes? Thanks,
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woofy
New member
Hey Jeff, where should i start trouble shooting for a ca0252 and gar1731? I built a decent amount of these and they all work but these two. The 0252 is creating lots of hum in both a vp25 and vp28 (pre amps are working as ive slotted and reslotted op amps till i narrowed it down to the ca0252 and gar1731 being the (seperate) problems).
I have checked them over for solder bridges etc and dont see anything. In fact the 0252 is my cleanest work to date, of course its the messed up one lol.
The 0252 in both the vp25 and 28 is giving me a crazy noise floor, and loud pops when i hit the mute button, or almost anything on the pre for that matter.
The 1731 in a vp25 didnt pass audio, or extremely low volume with the pre cranked. Same situation in the 28 fader position.
Thanks!
I have checked them over for solder bridges etc and dont see anything. In fact the 0252 is my cleanest work to date, of course its the messed up one lol.
The 0252 in both the vp25 and 28 is giving me a crazy noise floor, and loud pops when i hit the mute button, or almost anything on the pre for that matter.
The 1731 in a vp25 didnt pass audio, or extremely low volume with the pre cranked. Same situation in the 28 fader position.
Thanks!
I'd suggest triple checking all resistor placements as well as transistors. Short of that trying to hunt thru the circuit is tough. I know you can test transistors in circuit but not sure how to direct you thru that.
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