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Frankenstein Pioneer SX 737

Discussion in 'Pioneer Audio' started by rossm, Oct 7, 2018.

  1. cuda440

    cuda440 AK Subscriber Subscriber

    Messages:
    181
    Location:
    San Jose, CA
    I've never experienced a failure myself, but I understand they do fail and it's often with a "pop". Smoke may be involved.
     

     

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  2. rossm

    rossm AK Subscriber Subscriber

    Messages:
    273
    You guys were right! I was able to straighten the bent switch shafts
    A3E9F1D6-D1F7-4F5E-9CDA-EF395407AD31.jpeg

    Didn’t have as much luck with the front, was able to clamp it straight but it returned to it’s bent state once I removed the clamp
    73702EF5-26E4-4A3A-8FF2-39C94523C6EC.jpeg
    6E60E46B-32E4-4813-BB08-DBEF73528E34.jpeg
    449032DF-9091-494F-9136-7247C9DEDE81.jpeg

    Also with the exception of of 6 caps I have recapped all of of the electrolytic caps. Will have to wait on the next mouser order. Should I look at replacing the titanium caps also ?
    I have been powering up between boards and everything still works B6895987-9A83-402A-8777-BCF1C92EC8BE.jpeg 7E89C07F-ECE7-44F9-964B-20C6C7A8887D.jpeg
     
  3. EngineerNate

    EngineerNate AK Subscriber Subscriber

    Messages:
    3,137
    Tantalums of that era have a tendency to fail spectacularly, sometimes short circuit.

    That faceplate is probably done. You'd have to pull it out past straight and let it spring back to straight to get it to stay. It's unlikely you'd be able to do that without damaging it further.
     
  4. rossm

    rossm AK Subscriber Subscriber

    Messages:
    273
    Hi
    Are the little blue caps on the control amp assembly c1 c2 c23 c24 tantalum ? Or electrolytic?
    They have a plus side marked.
    I replaced the ones on the amp board c1, c2 with electrolytic
    Thanks
     
  5. ivandezande

    ivandezande Super Member

    Messages:
    1,703
    Location:
    Twin Cities
    The small blue, drop shaped ones are all tantalum. Get rid of em'
    Electrolytic's are 99% cylindrical.
     
  6. john stumpf

    john stumpf AK Subscriber Subscriber

    Messages:
    660
    Location:
    philippines
    as far as the face plate goes you wont be able t straighten that very well as the top edge and the face form a right angle which is strong but the force necessary to bend it in the first place caused the face to STRETCH. trying to bend it straight again forces the face to COMPRESS which it wont do unless it buckles.either way it will look like hell but it was worth a try.it. sure is a shame what people do to these things
     

     

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  7. Watthour

    Watthour Electron Rancher - JS3600

    You will likely have to bend the upper rail of the faceplate past center since it will tend to spring back once the pressure is released. It is less likely that the material is stretched, and more probable that the stiles (left and right) of the faceplate have been pulled inward, making the task a bit more challenging.

    Gauging the scale of the photos, it appears that there is about 3/8" of spring back, so the fixture may have to be arranged to take the upper rail about 3/8" past straight to allow for the spring back. I'd try 1/4" first to see how close to straight you can make it, then increase the bend if necessary.
     
  8. Eastham

    Eastham More Class-A than ever!

    Messages:
    2,195
    Location:
    North West UK
    I think you should leave the front panel bent with the broken glass, looks kinda cool to be honest.
     
    0Hz likes this.
  9. eiraved

    eiraved Plane Whisperer Subscriber

    Messages:
    2,251
    Location:
    Antelope Valley, CA
    There's one chance at straightening that top edge of the face, and that is the bent part would need to be taken "past center" with some heat applied to the bend. The plastic piece would have to be removed first obviously, then jury-rig something which would spread from the inside of the glass frame to take that bent edge past center. Spread the frame while applying heat to the bend using a mild torch, being careful not to get too hot and discolor the metal. Yes it's risky, but what have you got to lose?
     
  10. rossm

    rossm AK Subscriber Subscriber

    Messages:
    273
    Halloween is almost here and I am almost done !
    All electrolytic caps wither the exception of 1 on the tuner board has been replaced and every thing is working good.
    As suggested I got rid rid of the tantalum caps, did a little research and found out they are indeed electrolytic caps. They use tantalum as the dielectic where’s the others use aluminum. Always something to learn
    B00CCC81-A435-4646-B280-DF0021C3A9E3.jpeg 00B9A872-EA6B-44C0-B75B-7FCAA816B7E9.jpeg C6273DC1-1526-406A-A695-9A7FDA835A72.jpeg
    Some of the small caps on the tuner board were off by over 50%
    I have also replaced the grease on the main transistor heat sinks. Still need to replace variable resistors on the amplifier board. Not looking forward to putting the tuner dial string back on.
     
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  11. Watthour

    Watthour Electron Rancher - JS3600

    Looks like good progress!
     

     

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  12. rossm

    rossm AK Subscriber Subscriber

    Messages:
    273
    Well I missed my October 31 date, but it’s done now !
    B8024ACB-35E6-462A-BE56-E1E101F03F2E.jpeg 0F6E764B-EDCD-408D-A574-18B14DE40939.jpeg 303BC5F4-3221-4821-8511-E210389F3E05.jpeg

    All electrolytics except for the 2 main ones replaced

    I was really proud of myself getting the dial cord rewound correctly, hopefully the rest will be easier
    559E1B1D-9CAD-4225-A52F-44E434627C16.jpeg

    At some point I will have to make a walnut case for it, as both of the cases were pretty bad. A couple of nicks in the top of front panel but looks pretty clean to me. Sounds pretty nice as well !! Not bad for some thing that was headed for the scrap yard.

    F6ED7F92-5B95-42DF-8026-A29CB18DBB66.jpeg 8C486AAC-5BCA-47C3-93F4-FF0196C1C805.jpeg
    Thanks for help and following along
     
  13. redk9258

    redk9258 AK Subscriber Subscriber

    Messages:
    1,573
    Location:
    Illinois, close to St. Louis.
    So, is this the same aluminum face that was bent?
     
  14. Eastham

    Eastham More Class-A than ever!

    Messages:
    2,195
    Location:
    North West UK
    You should replace those silver can 2SC1451's on the power amp board, they're known for going bad, infact one of the 1451's in my SA-7500 went bad recently best replace them with a pair of KSC3503's, did this in my SX-737 aswell as preventative maintenance.
     
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  15. rossm

    rossm AK Subscriber Subscriber

    Messages:
    273
    No I wished I could have fixed it, but it’s just too bad
     
  16. rossm

    rossm AK Subscriber Subscriber

    Messages:
    273
    Yea, but it sounds so sweet now, I hate to make any more changes
     

     

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  17. Eastham

    Eastham More Class-A than ever!

    Messages:
    2,195
    Location:
    North West UK
    Changing transistors won't affect the sound. If anything it'll sound better. I did a full restoration on my SA-7500 and I can say for certain it was for the better, especially replacing the filter caps, bass was much punchier and less boomey.
     
  18. eiraved

    eiraved Plane Whisperer Subscriber

    Messages:
    2,251
    Location:
    Antelope Valley, CA
    Too bad you closed her up. With the age of this receiver, you should replace those cans also. As @Eastham indicated, you should hear an improvement in the lower frequencies once replaced. I have a bunch of extras that may be a match, if you want to change them out.
     
    Eastham likes this.
  19. Eastham

    Eastham More Class-A than ever!

    Messages:
    2,195
    Location:
    North West UK
    Not only that but quiter passages in songs are clearer too, I was listening to Pink Floyd The Wall and noticed how easier it was to understand the background vocals and insturments, like the voices from the TV's and the children in The Happiest Days Of Our Lives. Like it became less distorted and clearer. With headphones it sound identical to having my headphones plugged directly into my DAC.
     
  20. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

    Messages:
    4,613
    Location:
    Milwaukee, WI
    The 1451s are poison. You should 100% replace them.
     
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