Recently Restored SA-9900 working great now blowing fuses

Discussion in 'Pioneer Audio' started by Fhamre, Jun 19, 2017.

  1. rjsalvi

    rjsalvi Active Member

    Messages:
    233
    You might ask the owner which Pro-ject preamp he was using because they make quite a few of them...then check it out to see if there's any way and end user can muck things up. And in chorus with slimecity, can you be sure it wasn't operator error? Also, did you boot the unit up with a DBT before replacing the possible errant output transistors? Where is the unit plugged in for power? Straight into the wall? a line conditioner? a surge protector? Is there a possible short in the interconnects he was using to plug the TT preamp in?

    Having said all that and judging the end user alone based on the crate you received the unit back in, he appears to be a meticulous individual with an attention to detail. fwiw...
     
  2. Fhamre

    Fhamre Super Member

    Yes there are lots of possibilities. And I have tried to explore them all. I will keep testing it for about a week or so. I have been using my scope to try and see if the tone controls are playing a role but nothing observed at this point.
    Before it goes back I intend to replace all the outputs with OnSemi 95/96's and change the bias trimmers.
     
  3. Fhamre

    Fhamre Super Member

    Still not able to determine if this amp is ready to send back. It seems to be running fine.
     
  4. kevin_09

    kevin_09 New Member

    Messages:
    28
    Location:
    Atlanta GA
    I try to find the 8a 125v fuse, but it was too small compare to the original one. Can I use 8a 250v for it? or which size of fuse can I replace?
     
  5. rjsalvi

    rjsalvi Active Member

    Messages:
    233
    8A @ 250V is fine.
     
  6. Fhamre

    Fhamre Super Member

    Yup!
     
  7. kevin_09

    kevin_09 New Member

    Messages:
    28
    Location:
    Atlanta GA
    but how come when I replaced with 8a 250v, its still blowing :(
     
  8. Fhamre

    Fhamre Super Member

    You likely have shorted outputs. Do not power it up until a competent tech has checked it out!Something is amiss.
     
  9. rjsalvi

    rjsalvi Active Member

    Messages:
    233
    It's not the voltage that's blowing it, it's the current draw (amps). And no, you cannot use a larger amperage fuse because if you have a short, a higher (amp) rated fuse will allow more current to flow where it's not supposed to, and you'll end up burning up more of the circuitry. I don't know your level of expertise, but if you're sure you want to continue the repair, you'll need a DBT (Dim Bulb Tester) and how it's used, a multimeter, and knowledge of how to test individual components (like resistors, transistors, diodes, caps) with the multimeter. The most effective and least costly component you'll need to perform this repair, is time.
     
  10. kevin_09

    kevin_09 New Member

    Messages:
    28
    Location:
    Atlanta GA
    So what I have to do now? should i take it to the repair shop? because I did bought the 8a 125v fuse, but it is smaller than the original one. and it was not fit.
     
  11. rjsalvi

    rjsalvi Active Member

    Messages:
    233
    If you don't feel comfortable performing the repair, taking it to a shop is one option. Another option would be to start a new thread and ask if there are any audio repair specialists close to Atlanta. If any techs respond, you can check their posting history for credibility, or if anyone recommends a tech, PM them and ask if they were satisfied with the work. Or, you can sell the receiver as-is. Best of luck.
     
  12. Fhamre

    Fhamre Super Member

    You own a very nice piece. Well worth investing to have it properly restored. Just repairing it will not keep it running for the long term. There are heat issues on the power supply board and a lot of transistors that should be replaced including I suspect the outputs. That said said all the parts are available and after 40 years it will benefit greatly from a recap/restoration.
    You need to try and find the right person to do the restoration if you are not up to it. The 9900 is not the easiest piece to work on. I am sure this forum can lead to the right person. gl
     

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