Sony PS-X6

[Sam Cogley]

3.82 ohms is close enough to 3.9. I suspect Q101 and/or Q102 are blown. The model of those transistors should be in the parts list. It will be something like 2SC_____ or C______.

Considering the issues you're having with this power supply, and the fact that at least some semiconductors appear to be lunched, I would probably replace Q101-Q105 and D101-D105. It's a small number of parts, and you'll know that they're all fresh and not subjected to any power spikes or other abuse.

 

[Grotus]

3.82 ohms is close enough to 3.9. I suspect Q101 and/or Q102 are blown. The model of those transistors should be in the parts list. It will be something like 2SC_____ or C______.

Considering the issues you're having with this power supply, and the fact that at least some semiconductors appear to be lunched, I would probably replace Q101-Q105 and D101-D105. It's a small number of parts, and you'll know that they're all fresh and not subjected to any power spikes or other abuse.

Thanks, Sam, I'll start to put an order together. Dave's been guiding me so far, so I'll ask his opinion, as well, no offense intended.

 

[Grotus]

Yep, that's the procedure.

Cheers,

David

David,

You on board with Sam's advice to replace Q101-105 and D101-105?

Thanks,

G

 

[dshoaf]

Yes, you can swap all of those devices but would do it one at a time with testing in between. The logic, here, is that you can introduce more problems 'shot gunning' the power supply than you fix if there isn't some diligence applied in the process.

I'd suggest swapping the electrolytic caps first. They age faster and are almost 40 years old now. Again, do one at a time with testing in between.

Cheers,

David

 

[Sam Cogley]

Thanks, Sam, I'll start to put an order together. Dave's been guiding me so far, so I'll ask his opinion, as well, no offense intended.

No offense at all. I've been watching this thread, as I've dealt with similar issues in several direct-drive turntables. It's possible for only one transistor or diode to fail, but usually in power supplies like this, my experience is that if something shocked the system hard enough to start blowing power supply semiconductors, they're all suspect. Judging by the voltages you're reporting, where they're out of spec, and how much they're out of spec, it looks like either or both transistors in the pairs Q101/Q102 and Q104/Q105 aren't conducting properly, or have shorted junctions. You have reasonable, if slightly low, voltages after the rectifiers. As soon as you get to any test points past the paired regulators, things go haywire.

As far as the caps are concerned, I would have probably changed them out before I started testing anything. DD turntables are notoriously finicky about caps that are even slightly out of spec. Even caps that test good on a meter can be dysfunctional enough to cause problems. I've worked on a Sony PS-X70, X50, and 4300; Dual 721; Technics SP-10Mk.II, and SL-QD33, and a JVC QL-L1. Of those, every one had issues ranging from mildly odd behavior to full-on dysfunction before a recap of the power supply, save the 721, and it has a bit of a speed drift issue. I just haven't torn into it yet.

 

[Grotus]

Yes, you can swap all of those devices but would do it one at a time with testing in between. The logic, here, is that you can introduce more problems 'shot gunning' the power supply than you fix if there isn't some diligence applied in the process.

I'd suggest swapping the electrolytic caps first. They age faster and are almost 40 years old now. Again, do one at a time with testing in between.

Cheers,

David

Gents,

Took your advice, and replaced the electrolytic caps only (C102-C105), did it one at a time per David's counsel, and tested after every change. Even managed to shock the hell out of myself once!

As for the results, all measurements stayed the same. So it's on to changing out Q101-105 and D101-105. One at a time, of course, with testing after every change.

I'll post results when I have them.

Thanks,

G

 

[Sam Cogley]

I would get a cheap multimeter that includes a transistor test function and test each transistor as you pull it. Whatever is damaged will show up pretty quickly.

Something like these:
http://www.harborfreight.com/7-function-digital-multimeter-90899.html
http://www.harborfreight.com/11-function-digital-multimeter-with-audible-continuity-61593.html

 

[Grotus]

I would get a cheap multimeter that includes a transistor test function and test each transistor as you pull it. Whatever is damaged will show up pretty quickly.

Something like these:
http://www.harborfreight.com/7-function-digital-multimeter-90899.html
http://www.harborfreight.com/11-function-digital-multimeter-with-audible-continuity-61593.html

A standard multi-meter doesn't have that test setting?

 

[Sam Cogley]

A standard multi-meter doesn't have that test setting?

Most of them can test diodes, which you can use to do a transistor test by switching leads around. Having a plug-in transistor test is handy and fast.

 

[Grotus]

Most of them can test diodes, which you can use to do a transistor test by switching leads around. Having a plug-in transistor test is handy and fast.

Been a while, but update time. I replaced those transistors, and now the unit is totally dead. Power light won't even come on.

All voltages have stayed the same. I guess I should go ahead and replace the diodes now?