Recently acquired sx-1080 is a mess inside/ need a lot of help on this one

Discussion in 'Pioneer Audio' started by Jefferylu98, Sep 28, 2017.

  1. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    hello again all, I recently picked up a 1080 on the cheep that is at least a 9 on the outside and clean as a whistle inside, but it has many issues inside. I believe this has went across somebody's bench at some time. Owner said it don't work and he don't know anything about it. Lol. Here are the issues I found after a good visual inspection.(I have not plugged this unit in either) both amp boards unplugged-rear jumpers missing- right amp board has burnt r15-looks like a newer q5 in same board-missing pa1001a chip on tuner board(ouch) and the protection board has been pulled away from the plastic holders but looks intact. I need to know where to start on this basket case. I may have a downer board from a smaller model for the chip. This one may never sing again. Fingers crossed. Thanks guys for any input
     

     

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  2. tsd71

    tsd71 RIP Tom Petty Subscriber

    Messages:
    2,564
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    DONT PLUG IT IN UNTIL YOU BUILD A DIM BULB TESTER
     
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  3. basil13

    basil13 Active Member

    Messages:
    110
    Location:
    Ontario, Canada
    I would start by checking the output transistors. If they are bad, it may determine if you want to go further since they are unobtainable and requires a major work around to replace them.

    It has been awhile since I checked them but they are unique with four terminals including two collectors (one is the case). I don't remember the layout of the pins but you can perform simple diode tests. Maybe someone will chime in or you can search the web for the layout.

    Fingers crossed, good luck!
     
  4. markthefixer

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

    Messages:
    21,009
    Location:
    Bensenville,Illinois
    The Output Transistor work around isn't that bad. Get the service manual.
    They are NOT the 4 pin transistor cases found on the sx-1980 and sx-1280, but rather clamped down batwing cases with a BCE layout.
    The replacement's cases need different clamp bars. I have documented them somewhere in the forum. I'm looking for it, but a LOT of
    pictures have not survived over the years.


    That PA1001a is the stereo decoder chip and isn't hard to obtain from a plethora of donor models.
    It's the PA1002 that is found only on TOTL models and harder to source.
     
  5. john stumpf

    john stumpf AK Subscriber Subscriber

    Messages:
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    Location:
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    i do hope you find it mark,im trying as we speak to figure out the same thing!
     
  6. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    I have a dim bulb tester already, should I start at the power supply first and work my way thru this thing??
     

     

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  7. john stumpf

    john stumpf AK Subscriber Subscriber

    Messages:
    586
    Location:
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    if it works yes, but its generally considered to be best practice to repair whats wrong with it first. i would check the power supply voltages. but does it pass the dim bulb test? and if it does does come out of protection?
     
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  8. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    Ok, I plugged this baby in to a dbt and I have zero anything, DOA. I checked the fuse in the back of the multi voltage switch and that is good and I checked all the fuses on the psb and thy are good. NOW WHAT??
     
  9. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    Should I leave the amps unplugged for now?
     
  10. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    26,126
    Location:
    uk.. the middle bit
    checking supply voltages is next job .. yes leave amps out of circuit .
     
  11. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    Ok I finally got off the overtime at work and have some time to look at this mess. I have ac power to the main power switch and to pin 13 on the protection board when switched to on, but no power to pin 14 after the relay also pin 12 has 0 power. This thing is dead. Lol. Thanks for any input at this point. I am using a dbt.
     

     

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  12. rcs16

    rcs16 Super Member

    Messages:
    3,633
    Location:
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    Study the schematic, follow the flow, this model has a soft start ckt, current passes through the big 20W R to the transformer primary windings. This is for a very short period of time until the DC reg supplies come up and close the relay which shorts out the big 20W R. if the PS does not come up to proper V to close the relay, this is a fault condition, the big 20W R heats up, there is a safety feature, a thermal fuse attached to the big R that is wired in series, it will open if this fault condition occurs. It could be a fuse for the DC supplies. It could be afaulty PS, if so you have to check these things to fix if this is the issue, the thermal fuse has to be checked/replaced and you have to re-build the PS if that is it, so that the +60VDC ckt works and can power the S/S relay.
     
  13. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    Ok, I think I found an issue, the 20 w cement resistor on the protection board has flew the coop I believe. I pulled it out of circuit and it reads .624m ohms. Should be 3.3k ohms?? I checked the thermal fuse (out of circuit) and it passes current just fine, so I think that is ok. Any ideas for a replacement for cement block resistor? I guess this a start at least. Thanks for any and all help.
     
  14. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    Btw = this model has the multi voltage dial and I can’t find the correct schematics for the psb and protection board. It’s a little different from the standard schematics
     
  15. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    Ok, I have a little update. I installed the 3.3k ohm cement resistor and nothing. I jumpered the thermal fuse under the cement resistor and the relay activated. Yeeha, but then the above mentioned Burt resistors on the right amp board started the the white smoking. They are r-14 and 15 on the right amp board. Btw, q5 looks like a newer one as well as the resistors are not original. Done for the night. I’ll have to look at the schematic tomorrow. Any input would be great as to the next move.. thanks in advance
     
  16. petehall347

    petehall347 the brandy coffee man Subscriber

    Messages:
    26,126
    Location:
    uk.. the middle bit
    r-14 and 15 as you may know are acting as fuses so too much current from short or something
     

     

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  17. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
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    Location:
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    That 20 Watt resistor in the soft start circuit is 3.3 ohms not 3.3K ohms. Also don't leave the thermal fuse bypassed after your trouble-shooting is done, replace it if it is bad. It s a fire hazard if the soft start relay does not close with that thermal fuse bypassed.
     
  18. rcs16

    rcs16 Super Member

    Messages:
    3,633
    Location:
    Baldwin, Ontario, Canada
    The thermal fuse (105C) must be in contact with the 3R3/20W for the circuit to be safe. the new pcb's, have the R sitting on top of the TF, older ones have it touching with high temp/non-combustible material
     
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  19. DUALityOFman

    DUALityOFman Active Member

    Messages:
    176
    Yikes. I am picking up a 1080 tomorrow, but reading this is making me scratch my head. The one I'm buying is working as it should, but it hasn't had a major service/shop. Reading this thread reminds me of that Tom Hanks movie, The Money Pit.
     
  20. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
    155
    Location:
    Port Huron, Michigan
    Merry Xmas everybody. Ok I replaced the the thermal fuse and the cement resistor with the correct one 3.3 ohm. I have the same results as before. R 14/15 start smoking (right amp board). Pulled them out and they tested right at 150 ohms but are burnt also pulled q5 as it was obviously been replaced . Left amp board looks just fine. Somebody has defiantly been on this right amp board playing around. Not sure which way to go with this now. Please help with direction forward. Thanks and have a great holidays.
     
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