Hello people! I recently restored a 4.6 pre (recap, deox, cleaning, etc.). Everything was fine, sounding excellent, when the oscilloscope probe’s crocodile broke away from ground and touched one of the power supply transistors, causing a spark. From then on it turns on, but only works in Straightwire mode. The power supply works properly. I can’t find the schematics and/or service manual. Do any of you have it? He would forever be in my prayers.
Hi Mephysto,
I managed to get my hands on what looks like the hand drawn schematics from a PS audio employee several years ago. I also have a copy of the 5.0 manual which was an almost identical preamp.
If you’re interested in seeing what I have, just let me know.
What did you end up using for caps (brand?)?
I recently completed a full restoration on my PS Audio 4.6. It’s totally worth saving.
I have the Schematics from HiFi Engine that I cleaned up for the amplifier stages, but sadly the power supply isn’t documented. Let me know if you want these.
It may sound extreme, but you may just want to swap out all of the transistors as one or more of these likely took the hit. Ace Electronics (ace4parts dot com) in Houston has a large supply of NOS Motorola MPS8099 and MPS8599s.
I just went through and swapped all of these out on mine and found that a lot of them were out of spec, and one had an hFE of 2 - resulting in a bad channel. All fixed and possibly better than new I think!
Hey LJR3000 - I’d love to get a copy to cross reference with what I have. And Paul, if you’re listening - do you guys have a copy of the service manual in the archive? That would be an amazing resource! 