Noob repair help - SX-980

Discussion in 'Pioneer Audio' started by soulscratch, Aug 10, 2017.

  1. soulscratch

    soulscratch New Member

    Messages:
    18
    Hey guys!

    I've had multiple people tell me to head your way for help and advice, so here I am!

    Yesterday, I stumbled across a local ad for an SX-980 for $100 in working condition. I thought it was too good to be true but I think the guy just didn't know what he was selling. Externally, it's in fantastic condition. Very minor wear. Internally, however, is a bit different. After I got it home, it became clear that the previous owner was a smoker (we met at a parking lot so I didn't notice it then, not that it would have changed my mind). It's pretty grimy in there and I'd like to figure out if I can fix that. I also noticed that the 2200 μF cap on the power supply board (correct me if I'm wrong) is starting to bulge and I figured it's best to be safe and fix that before I power this thing on. I'm a pretty DIY person and I'd like to try to take a crack at this, but electronics are my least knowledgeable subject and due to the value of the unit and scarcity of some of the parts, that has me worried. I do have a nice Hakko soldering station and multimeter so I think I have what I need to get started - I'm just worried about my skill level and lack of knowledge, but I'm willing to learn.

    With that said, I have a few questions:

    1) Removing the board and replacing that capacitor should be pretty straight forward, correct? I can test the other caps while I'm in there. Is there a specific cap I should look for to replace this one with? As long as it's not too expensive, I'm willing to spend the money on it.

    2) The internals are pretty filthy and I'd like to clean it up. I know a lot of the old arcade cabinet guys go through and wash up the circuit boards. What are my options here? Also, should disassembling and reassembling be pretty straight forward?

    3) Two of the indicator lights are out (Aux and AM from what I'm told). I noticed some LED replacement kits on eBay. Worth it?

    4) Is there anything else I should be doing while I'm in here? Upgrades, repairs, replacements, or testing?

    I apologize for the long post. I'm hoping to have some knowledge dumped on me, so let me have it! Also, I'm going to have some seriously noobish questions, so just be prepared.

    And a few pics to make this post worthy of your time:

    Here she is in all her vintage glory:

    [​IMG]

    Power supply board with the bad cap:

    [​IMG]

    A lot of grime:

    [​IMG]

    [​IMG]

    Thanks in advance for any help and input!
     
  2. markthefixer

    markthefixer On Hiatus, dealing with Dad's estate full time Subscriber

    Messages:
    20,587
    Location:
    Bensenville,Illinois
    Those "bulging" caps in the picture are not really bulging, the appearance insert is being bowed by the shrink wrap label pinching it. Yes, they put the labels on the caps with shrink tubing. After years and heat they shrink enough to cause the doming of appearance inserts - otherwise bare aluminum would be visible, like in a lot of modern caps. Granted the caps should be replaced, but for other reasons.

    Also in your LAST picture, the STV-4H thermal bias diode is in the lower right corner - mounted by a screw to the heat sink.
    DANGER!! The leads LOVE to break off flush to the body of the diode, so be very careful about moving the wires when cleaning - do NOT bend the last 1/2 of an inch of those wires where they enter the diode!!
    Best practice is to loosen the screw and tuck the diode safely away while not bending the wires anywhere near the diode body.
    The STV-4H has no ready replacement (unlike the STV-3H which a supply was found that hasn't yet been exhausted) and I have had some success in repairing them - BUT the best case is to NOT break them!!
     
  3. soulscratch

    soulscratch New Member

    Messages:
    18
    Wow, that's great! I was actually poking at the top of the 63v caps because I was thinking that maybe they were starting to bulge, but the plastic on the top was flexible and moving up and down. I think you are right about that cap on the power supply board. That's awesome.

    As far as the diodes, I wish I could say I knew what you are talking about but I have no idea. I can snap better pictures in the morning and maybe you could draw a circle for me?

    Also, any advice for cleaning everything out?
     
  4. soulscratch

    soulscratch New Member

    Messages:
    18
    Oh, I think I see what you are talking about. The blurry black screw head in the bottom right, facing up. Are you saying I should loosen the screw and carefully rotate the diode 90 degrees ccw?
     
  5. soulscratch

    soulscratch New Member

    Messages:
    18
    Ok, now I'm scared to death to touch this thing. If I just don't get near it and leave it alone, will I be safe?

    [​IMG]
     
  6. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
    4,113
    Location:
    Las Vegas Nevada
    It is a little crusty in there. Blow it out with some compressed air. Be careful of the diodes Mark had mentioned.
    There is a Sticky on cleaning the receivers. Check out the Solid State forum for the thread.
     
  7. soulscratch

    soulscratch New Member

    Messages:
    18
    You have a link by chance? I did a search on the Solid State forum but nothing official popped up that I could see and I'd love to take a look.
     
  8. zebulon1

    zebulon1 Cleaned up the shop and half finished sets. Subscriber

    Messages:
    4,113
    Location:
    Las Vegas Nevada
  9. Awesomeaudio

    Awesomeaudio AK Subscriber Subscriber

    Messages:
    953
    Location:
    Sydney, Australia
    Looks like photo bucket is wreaking havoc in that DIY thread too.
    Time for a world wide boycott of P.B.
    Soulscratch.
    Don't be afraid to tackle this thing.
    You seem capable enough.
    Just follow the instructions from the guys and you'll be fine.
    You have a nice unit. Congratulations.
     
  10. mquinn25

    mquinn25 New Member

    Messages:
    20
    soulscratch...I was scared to death to mess with my SX-3900, but I am really glad I did. I am no expert electronics technician. I rebuilt the power supply, cleaned the pots and switches and replaced all the lamps and cleaned. I even bought a re-wrap tool on Amazon to re-wrap the wires. I would HIGHLY recommend Dave (dwojo) for bulbs. He will know exactly what you need, and it will make it look really nice! As far as caps go...you will not be able to test them in-line without a meter designed to do that, meaning if you are using a regular multimeter you would have to take them out to test them properly. My opinion is if they are not bulging or leaking and the board seems ok leave them alone (others will disagree), and if I have to take a board out to replace a cap, I replace them all on that board. I had enough issues with my PS board that I replaced all caps and power transistors due to extreme heat and failure of the board. This is a BEAUTIFUL receiver! Go slow...be careful...take pictures, sort parts...you will be fine. :)

    Let us know how it works out!

    Mike
     
  11. mquinn25

    mquinn25 New Member

    Messages:
    20
    ...and I agree with Mark...your caps look fine in those pics. I love that Receiver!
     

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