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SX-980 Tuner issues after having fixed a PS issue. It's a long story...

Discussion in 'Pioneer Audio' started by Ricktptman, Jun 14, 2018.

  1. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Hi everybody,
    This receiver was probably the second or third SX-x(x)80 vintage receiver I bought and restored. It developed a Power Supply issue at some point (This was in 2003 or thereabouts and UPS seemed to live to destroy vintage receivers, this was one of them) so I put it in my "someday" stack of things to do. Someday's here. When I fixed the Power Supply problem, a fuse blew elsewhere (this was about eight years ago) and I lost functionality in the following: 1. The source "light bar". (FM,AM,AUX,Phono1,Phono2), 2. The Stereo carrier portion of the FM signal. (Not the light, the carrier. It doesn't appear to be the alignment.) 3. The ability to align the Center Tune meter. (The center tune meter adjustment doesn't work.) 4. (New) I forgot to include that the FM only passes signal with the Muting OFF. I've replaced all the fuses, but I haven't DeOxit-ed it, yet, though. Other than that, everything's lovely. I've got at least one very nice sample of every SX- xx80 series and this one is the next thing (and the least "very nice" but it's still "pretty nice/okay") on my bucket list so I'd like to check it off. Any help from the repair wizards here would be much appreciated. TIA...
     
    Last edited: Jun 15, 2018

     

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  2. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    All the issues relate to the 24 volt supply. Fuse 1A. Feeds, Tuner, protection and lights.
    You got something twisted in the circuit. Q5 and Q6, diode D6 and D7.
    DBT?
     
  3. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Thanks, I'll check it.
     
  4. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Deoxit didn't help, but I didn't expect it to. I'm checking the Transistors and Diodes now. I'll post back. DBT=Defect Based Testing? Yeah, pretty much. Before I measure, I like to poke and prod. Sometimes it saves a boatload of trouble.
     
  5. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Not sure what your voltages are but with the lights out it must be missing.
    The tuner runs on 13v's and anymore can fry the PA chips. Better check it.
    The DBT can help warn of a short once you made any repairs. I highly recommend having or building one.
     
  6. mattsd

    mattsd AK Subscriber Subscriber

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  7. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Thanks for that. I think if I'd had one before, this could've been avoided. I'll take a look at it.
     
  8. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    I removed the transistors and put them in a tester and they checked PNP/good. But this RS DMM read all over the place in terms of value. But they did appear to be functioning. I put them back and the Transistors seemed to check out in the circuit. I replaced a Diode (I'd bought some in the way back and left the envelope with the receiver) but they don't look like the originals. Update: They weren't correct and were shipped as subs for the Diodes for which I'd asked. (That'll teach me...it was at least 10 years ago) I had some extra 10E2's from a parts 780 and when I dropped that in, the FM MPX Muting engaged setting started to pass signal and (I had to change the bulb) FM Stereo Indicator light are once again live and working fine. With that fixed it allowed me to realign the Center Tune meter. So...that leaves the four Source lights...I've searched for other threads, but now that it's the ONLY thing keeping me from (where'd I put 'em?) reinstalling the knobs, switch covers and taking a victory lap, any help would still be very much appreciated. Thanks again, Matt and Zebulon1.
     
  9. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Look at the scat. R18 drops the 13 volts down to 7.5v for the four indicator/function lamps it taps off of Pin 18 of the PS.
    Be careful this time :cool: and check for voltage there. Maybe R18 is toast?

    zxxx.PNG
     
  10. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Thanks, I didn't cause the initial problems though, UPS's dropping it did, lol. But I think the second problem may have been a transistor that was squashed flat and it's possible two legs momentarily touched. I straightened/double checked all that stuff out when I went through it this time. (Experience helps!) It was when I was first starting out and I hated doing anything to PS's. I'm still not crazy about it, but I'm more careful now. I used it for a number of years before the second problem developed and I thought I'd get back to it before now. So the details are a little less sharp than before. I removed the blown diode and taped the (wrong, thanks Pioneer parts) diodes to the polybag I keep all my non-daily driver gear sealed up in. It wasn't until I looked closely that I realized it was missing the blown one. That's when I started taking a close look at the Pioneer Parts diodes and started looking for those salvaged E10-2's. I saw the other thread about that 1/2 watt 120 ohm Resistor. I've got a few ordered. I'll post back and thanks to everyone for their help!
     
  11. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    You've done a great job describing the issues and now you have another Pioneer back up and running. It's a waste to have them taking up space and not giving back.
    If it wasn't already positioned off the board, raise it up a wee bit and let get some air. It makes a big difference.
     
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  12. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    Will do, Zebulon1. AK is such an invaluable resource for these types of things. I'll post the results when they arrive. Hopefully, the resistor will resolve the problem. Thanks again to everybody who responded as well as those who've posted about these (and similar issues) in other threads. Every time the re-subscription prompt comes around, I hit the button. Best to everyone...
     
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  13. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    IMG_20180618_175802545_LI.jpg IMG_20180618_175834549.jpg
     

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  14. Ricktptman

    Ricktptman There are two kinds of Music: Good & Bad-Ellington Subscriber

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    You can see the UPS-ification of the walnut cabinet on the right-hand side. It's stronger now than it probably was when it was new, thanks to some Elmer's Wood Glue. But I couldn't quite get the split to disappear at the top. But the rest of it's pretty sweet. Only a few small dings here and there. Time to listen to something good, like maybe some Roulette Era Maynard... ; - )
     

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