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. markthefixer

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

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    NOT YET, the transistors pete posted about will probably not fit flat between the heat sink "fins"
    I was trying to show WHY NOT.

    You need to measure how much flat mounting space is OUTSIDE of the screws.
    It looks to me that the TO-247 transistor case will fit between the screws,
    I showed the RM60 case because it was used in the SX-3900, where I have successfully swapped the TO-247 transistors (from mouser or digikey) in.

    Here's what I did:

    original transistors (RM60) on an SX-3900 / D7000 with Phoenix socket replacement
    d7000_transistor_phoenix_socket.JPG


    TO-247 replacement transistors on the SX-3900 / SX-D7000 with Phoenix socket replacement
    Notice the aluminum hold down bar with 24.4mm screw spacing holding down the replacement transistors.
    aluminum.jpg
     
    Last edited: Feb 10, 2018

     

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  2. rcs16

    rcs16 Super Member

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    TO-264 is 20mm wide
    TO-3P is 15.6mm wide
    TO-247 is 16 mm wide, I think these are the one to use, Onsemi MJW3281A/MJW1302A (200W/230V/15A)
    make up that hold down plate(s) that Mark shows. Probably have to use longer screws, not sure what size it is (5mm?). new mica or sil pad, thermal compound (if using mica), do not over torque, check for continuity between the flange(collector) and HS (ground). See if they bias up to spec.
    test(diode test) out all the bjts/R's in the power amp. could check out DCV from the PS too.
     
  3. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    Port Huron, Michigan
    Hello all, I finally got off the overtime at work and get back to this monster. YAAAAAA
     
  4. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    Location:
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    I have a solid 1/4 inch (7mm) of flat clearance from the outside edge of the bolt holes. I have 3/4 inch (20mm) of clearence in between the bolt holes.
     
  5. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    Location:
    Port Huron, Michigan
    Hello All, I tried to locate the parts TO-247 that RSC16 recommended, Mouser says both are obsolete?? Does anybody have any recommendations for some replacements?? Sounds like I will be needing some mica pads also? The originals were mounted directly to the heat sink with thermal compound. Any help and recommendations would be very helpful. I am totally lost with this rework task. Thanks for any and all help with this one..
     
  6. merlynski

    merlynski Curmudgeon Electronicist Subscriber

    Messages:
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    Location:
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    Onsemi MJW3281AG and MJW1302AG ( note G at the end ) both show as active on Onsemi site, without G show as obsolete.
    Mouser shows 674 of MJW3281AG and 229 of MJW1302AG in stock as of 3/21/18.
    Mouser PN# 863-MJW3281AG and 863-MJW1302AG

    You must use thermal compound, even if you don't need/use a mica insulator.

    EDIT: more info
     
    Last edited: Mar 21, 2018

     

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  7. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    I have one prototype clamp done with the new mjw1302ac. I have the original plastic insulator in there ( no heat grease yet) let me know what what you think??? Looks like it will work to me, but I don't know crap. Lol. Please comment IMG_0003.JPG
     
  8. petehall347

    petehall347 the brandy coffee man Subscriber

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    uk.. the middle bit
    looks good to me .
     
  9. rcs16

    rcs16 Super Member

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    Just be careful with that insulator, do not torque the screws with no thermal paste, they can crack and cause shorts of the live tab to the heatsink which will be at ground potential.
    Also not over torque the screws once paste is applied. Always double check after assembly.
     
  10. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

    Messages:
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    Location:
    Port Huron, Michigan
    Thanks for the replies fellas, I will finish the hold down brackets and install on heatsink and reinstall in chassis. I will need some guidence for start up procedure. Should I replace the trimmers on the amp boards, if so with what model numbers?? I have 652-3296p-1-204lf. And. 652-3386h-1-101lf. Mouser part numbers. Have 2 each
     
  11. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    IMG_0005.JPG IMG_0004.JPG Afternoon all, I finished one side of heat sink. I have to finish drilling the last four aluminum clamps tonight. Here is a pic of my progress. It looks like there is no heat grease on there, but there is, I just took the time to clean up the excess with q tips. I think it came out fairly good. Comment if you like. Have a good night all.
     

     

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  12. rcs16

    rcs16 Super Member

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    looks good, measure ohms between clamp plate screws and bjt leads
    what did you use for insulators?
     
  13. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    Location:
    Port Huron, Michigan
    I measured OHMs on all 4 trans to ground. I have no readings on any of them. So, I assume they are installed correctly? I cleaned up and reused the factory isolators. Any idea or direction for the replacement of the trimmers on the amp boards?? I have some and I listed the part numbers in a couple of posts above. I think it would be a good idea to get these replaced while apart?? (Can’t hurt) thanks again for all the help
     
  14. basil13

    basil13 Active Member

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  15. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    Location:
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    image.jpg Ok, I have an update. I finished fabbing the clamps and have everything back together. I have not plugged in the amp boards yet. I was able to get the center voltage on both amps to 0 volts, the idle current is unadjustable on both amps. Do the amp boards have to be plugged in to get this to adjust 30mv with VR1??? I am not going further with this till I hear back from someone as I have too much time in this basket case. Lol. Thanks for the compliment basil13, I made the clamps out of some scrap aluminum I had in the garage.
     
  16. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Nice neat work, it's looking good.
    You need all the plugs connected on the amp boards for them to operate and adjust the Idles. You have the regulated in front and the unregulated in back, powering the outputs.
    Connect all the plugs on one amp board and use the DBT to power up.
    Check the DC Balance and check the idle trimmer response by starting it at full CCW and adjust CW watching the readings that they move smoothly and to the trimmer movement.
    If all is well. Adjust the idle trimmer back to min mV's and apply full house/line power, setting the idle to the final 30mV reading.
    Then move to the other channel and repeat.
    If the idle doesn't adjust or can't make the required setting, recheck your work looking for missed solder connections.
     

     

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  17. Jefferylu98

    Jefferylu98 AK Subscriber Subscriber

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    I CANT BELEIVEIT!!!!!!!! This thing actually is singing nicely now. I didn't think this thing would ever work again,but here it is back in service, thanks to all your help,THANKS SO MUCH. I'm speechless LOL. Gonna let it run for a bit and listen to some tunes while I clean up my bench.
     
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  18. zebulon1

    zebulon1 Getting behind on work. I need help? Subscriber

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    Great!
    Good thread, good work.
     
  19. rcs16

    rcs16 Super Member

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    Location:
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    Great to hear of success for this re-build.
    I am not sure of the trimpot part numbers. The value look okay, 100 ohm for bias and 20K for offset. See if they fit and allow easy adjustment.
    3296p-1-204lf. And. 652-3386h-1-101lf
    If the original pot cleaning makes them operate okay, I'd leave them in.
    Check idle/offset after it warms up to op temp (runs for a while), see how much it changes when it gets hot. should be set when at op temp.
     

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