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  1. creeve

    Another MA5100 one channel less wattage above 1k

    Yes, in a primitive sort of way. Since the right channel is fine I simply used the switch to sum to mono and also stereo reverse with no change. So that should have essentially thrown everything that was feeding the right channel over to the left leaving only the power amp to blame. Please...
  2. creeve

    Another MA5100 one channel less wattage above 1k

    Good evening all, While I am waiting to sort out getting some replacement to-66 driver transistors for my MA5100 I would like to bounce this one off some of the seasoned mac techs. Before my screwdriver accident that took out the drivers I was bench testing the amp after recapping the power...
  3. creeve

    MA5100 driver transistor subs - slip of a screwdriver = disaster

    well I just installed the drivers into the good channel. Although they are not shorted and passed a basic dmm test, they must have been injured because that channel becomes extremely unstable with them installed. DC offset swings from 4mv to over 200mv up and down erratically. power supply...
  4. creeve

    MA5100 driver transistor subs - slip of a screwdriver = disaster

    Well I am happy to report they all pass the 4 way dmm check. I am shocked considering I arced the screwdriver right through the base of one of them. They are apparently more robust than the outputs. I will install them on the good channel and see what happens. I would rather test with those...
  5. creeve

    MA5100 driver transistor subs - slip of a screwdriver = disaster

    BTW I am not afraid to convert to newer package style either. Despite my stupidity that caused this mess I am capable of such a conversion if such a thing is possible.
  6. creeve

    MA5100 driver transistor subs - slip of a screwdriver = disaster

    I will test them, so you would trust them if they pass a simple dmm diode test in all directions? I will report back later with the results. I thought I read a post somewhere in all of this that said mac no longer had subs for these either. I think in one of your older posts you were testing...
  7. creeve

    MA5100 driver transistor subs - slip of a screwdriver = disaster

    So I am an idiot, I am in the process of restoring this new piece in my collection and was scraping a solder blob off the chassis near the mounting nut for q27 aka q216 in the SM. Still had not discharged all the caps and shorted the base to ground, sparks flew and now I have shorted outputs on...
  8. creeve

    Pioneer pa1002a vs p1002 (non a version)

    Thanks.....I compared the voltages and they are similar but not all identical. Prob would work like you said but as it turns out I got lucky. When I opened up the tx8500ii it had the “a” module even though the schematic said it was the non “a”. The sx-980 now lives again. Now I’m left with an...
  9. creeve

    Pioneer pa1002a vs p1002 (non a version)

    Does anyone know if they are interchangeable. I have an sx-980 with a bad pa002a chip and may be able to get a donor to-8500ii tuner that has the non a version chip. They appear to do the same job but there has to be some difference I would think. Thanks much.
  10. creeve

    SX 980 protection circuit concern

    Yeah definitely went way past that. I will check the resistors. Only other thing I can think of is maybe because there was no load connected but that really doesn’t make sense either.
  11. creeve

    SX 980 protection circuit concern

    About 3.1v it trips. Just does not seem right.
  12. creeve

    SX 980 protection circuit concern

    Happy Memorial Day All! I have an sx 980 that I’m in the process of bringing back from the dead. It’s was a real basket case. Anyway after I rebuilt the amp boards with new caps and trim pots I fired it up and it had over 2 volts of dc offset on one of the channels BUT it came out of protect. I...
  13. creeve

    Pioneer sx-980 with a bad pa1002a chip :(

    Thanks so much. I think I got it. One question though, if I remove R59,61 then I don’t have to remove R60,73 correct?
  14. creeve

    Pioneer sx-980 with a bad pa1002a chip :(

    Nope thought the same thing yesterday. Not even the same pinout. Gonna try Rcs16 suggestion and see how it goes. At least then it will be usable until a chip or donor unit pops up.
  15. creeve

    Pioneer sx-980 with a bad pa1002a chip :(

    Sadly these appear to be unobtainium also. Actually called a supplier today that I found online and their website said they had a few.....guess what, it was a computer error as they have none.
  16. creeve

    Pioneer sx-980 with a bad pa1002a chip :(

    Sorry, I guess what I meant was can you walk me through what needs to be done? I just don’t want to make this thing any worse. Thanks for your help.
  17. creeve

    Pioneer sx-980 with a bad pa1002a chip :(

    So if I went a route like this I would lose muting functionality I assume, which is no big deal. Do you have a schematic? I am not very well versed in tuners beyond basic troubleshooting.
  18. creeve

    Pioneer sx-980 with a bad pa1002a chip :(

    Pete..all voltages are good, plus the left half of the chip is functioning fine. Was really hoping it was just a dirty switch but not so lucky.
  19. creeve

    Pioneer sx-980 with a bad pa1002a chip :(

    So as the title says I have an unfortunate problem. The pa1002a chip on the tuner has good signal going in but nothing coming out of pin 5, thus no right channel in FM stereo. This receiver had one foot in the grave when I got it and I’m not gonna give up on it yet. I have read some threads on...
  20. creeve

    Basket case sx-980 rehab. Dead right channel in FM

    Ok what would have to be done there? I would be up for modding the circuit so I can use it as long as it can be undone if I ever find the correct chip which looks unobtainium right now.
  21. creeve

    Basket case sx-980 rehab. Dead right channel in FM

    Anyone know If an NTE788 would work?
  22. creeve

    Basket case sx-980 rehab. Dead right channel in FM

    Well I have figured it out. The pa1002 audio amp is bad. No output off pin 5. Now to find a source for one.
  23. creeve

    Basket case sx-980 rehab. Dead right channel in FM

    Thanks Watthour. Yes I have signal at both of those points. I also checked the two 0.56 caps feeding the pa1002 and I have signal there also.
  24. creeve

    Basket case sx-980 treble and bass pots

    Thanks....will leave them be then. Believe me I have bigger problems with this beast to deal with.
  25. creeve

    Basket case sx-980 rehab. Dead right channel in FM

    That’s what I checked already. Pin 19 has audio, pin 21 is a no go. That’s why I need to start further probing back. Any safer areas you can think of? I think there are some bad caps on the board for sure, because even the good left channel take a bit to “warm up” before I get full volume...
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