mosfets
Active Member
I bought a circa 1978 Nikko Beta II preamp from the internet. The local seller said he was the original owner(he would have been under 10 years old when it was new). The cord was cut and extended, butcher job. Someone took it apart and put it back together with the facial grommet missing from the subsonic filter button(how does one do such a thing?). The seller said he pulled it out of storage some time ago and had it running in his system. He said it worked well but that was a while ago so he would not guarantee performance. Somebody was inside, those funny fingerprints on the metal work and the PCB tell me so. The phono section is completely destroyed and now I need a plan of attack to repair that portion. Hopefully I can get to it, this is a hobby.
2SA872s were replaced with matched KSA992s Q501, 502, 503, 504, 507, 508, 509 and Q10 are now all Hfe 400 and Vbe 652mV-ish(consult the service manual available online). I also dropped in some non-inductive audio grade PRP 1% resistors. The capacitors came from Digikey and Parts Connexion and the PRP resistors came from Parts Connexion. It sounds nice but I am curious to put it on a THD bench test for some numbers on paper. I'll get to that eventually. I ordered new grommets for the face from China. I think I might be able to make them work but time will tell.
Cheers.
2SA872s were replaced with matched KSA992s Q501, 502, 503, 504, 507, 508, 509 and Q10 are now all Hfe 400 and Vbe 652mV-ish(consult the service manual available online). I also dropped in some non-inductive audio grade PRP 1% resistors. The capacitors came from Digikey and Parts Connexion and the PRP resistors came from Parts Connexion. It sounds nice but I am curious to put it on a THD bench test for some numbers on paper. I'll get to that eventually. I ordered new grommets for the face from China. I think I might be able to make them work but time will tell.
Cheers.
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