Recently Restored SA-9900 working great now blowing fuses

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

  1. Fhamre

    Fhamre Super Member

    I recently did a restoration on a low miler SA-9900. Full recap,including ps caps. Removed all the known failure prone transistors. I ran and tested the unit for many hours. Sold it to a fellow across the country and he reported back how happy he is. The next day he reports that after he hooked up a Project tt pre amp through the AUX terminals and did some tone adjustments. It blew a fuse.
    Apparently it keeps blowing fuses now.Any thoughts?I have never used a tt pre amp through AUX before.
     
  2. markthefixer

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

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    It blows fuses. We have two "it's" here. I could assume you mean the SA-9900 is popping the fuse .

    The "Project tt pre amp" - that's the turntable with it's own preamp? With a line level output?

    Remember what I said in '14 about trimpots in that SA-9900? I hope you put in new idle current trimpots in this one?
     
  3. Fhamre

    Fhamre Super Member

    Yes its the 9900 blowing the fuse. It was working fine until the tt with the phono amp built in was hooked up.I didn't replace the trim pots as they were easy to adjust. I didn't come across your recommendation on those when I did my research. But I will look for that post,now.
     
  4. LesE

    LesE 110284 Subscriber

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    That's terribly unfortunate. I saw your listing and it looks like it's an excellent example of an SA-9900.

    If it was the main 8A fuse that went, I wouldn't have thought that connecting to an AUX port could cause it to blow. Perhaps something like an errant component lead clipping came loose during shipping and settled in a bad location. You may have to get it shipped back to you and then throw it on a DBT to determine what parts were damaged. Hopefully, your buyer has stopped replacing fuses.

    When I did my 9900, I replaced all 8 trimmers including the idle adjustment trimpots that Mark mentioned. The trimmers in the main regulated power supply were totally shot from heat.

    Good luck.

    Les.
     
  5. Fhamre

    Fhamre Super Member

    Well this one was such a low miler everything looked good. It was run for days at my end. He ran it yesterday and today moved it to another location and hooked things up the same way and ran it for awhile but when he started adjusting tone controls she blew.
     
  6. markthefixer

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

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    We won't know until you have it in hand, and then figure out what blew.
     
  7. Fhamre

    Fhamre Super Member

    Well the fellow took it in to a reputable shop and they found at least two outputs shorted. So now the unit will be shipped back to me.
    I know it will likely be a hunt to find what caused them to short. The only info I have is that the short occurred while the phono amp was hooked up and he was adjusting the tone controls when it happened.
    In the meantime I will replace all the outputs when the time comes. Recommendations?
    I have On Semi MJ21193/94 and 95/96 on hand.
    Here is a pic of the driver board after capping and transistor replacement.
    IMG_6910.JPG
     
  8. LesE

    LesE 110284 Subscriber

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    I would try to check every semiconductor and resistor on the power amp assembly. Before powering up on a DBT, I think I would separate the amp and the pre-amp just in case there is some unusual condition at the pre-amp output. If you have a scope, you could look at the pre-amp output while adjusting all of the controls. I think I would also have it on the DBT when reconnecting the amp and pre sections. You could then work the controls again while watching for any flashes of the bulb.

    Les
     
  9. MarZutra

    MarZutra Super Member

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    God I wish you luck. I really do. I had one of these and it turned out to be such a problem child that 3 techs took about a year, or better, working on it. After my last stint at one of the techs and their losing the top front cover plate...and it dying again... I ended up selling it on, with the TX9500ii for parts or repair. I was so pissed off at my 9900, though I am glad it went to a nice fellow who had been looking for a decent one for ages. Mine was - until the last tech got hold of it - was a 9/10 physically...
     
  10. Fhamre

    Fhamre Super Member

    Good advice,Les.
    Sorry about your 9900 issues Mar. I am confident with AK help we will sort this out. In the end it will be probably the guy in the mirrors fault. We shall see.
     
  11. fernarias

    fernarias AK Subscriber Subscriber

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    Did you check the transistor while you were restoring the unit? Especially the output transistor and the driver transistors(checking for gain and leakage is a good idea)?

    Transistors are beginning to fail on the old gear, not just caps. The SA-9500 that I just refurbished had two output transistors that were below spec (gain was 7 for one and 11 for the other and the rest were half the gain they would of had new) so I replaced all the output transistor (actually I replaced all the transistors). Yesterday, while taking picks of a Marantz 170DC, it blue up(I put LEDs and you know). A dual rectifier shorted and took out a few things (not many, well designed circuit). So lately I've been swapping out not just caps but transistor, zeners and rectifiers and it only takes a little extra time and money.

    A friend of mine, that I had recapped a Marantz 2235, decided to see how loud it could go and boom. Luckily I had replacements and it was after this that I got test gear to test transistors.
     
  12. Fhamre

    Fhamre Super Member

    Well the 9900 arrived today. In the finest custom built shipping crate I have come across.
    The main fuse blew due to two shorted outputs.
    So now I will begin to see what else was damaged and with your help hopefully the cause.
    IMG_7164.JPG IMG_7172.JPG
     
    eizner23 likes this.
  13. redk9258

    redk9258 Super Member

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    That is a damn fine looking crate! Kudos to the builder / packer!
     
  14. Fhamre

    Fhamre Super Member

    Well I did a little exploring looking for shorted components on the driver board. Everything looks good and tested good that I checked.
    I happened to find a pair of matching outputs from a Ca-1000 Yammy in my box. So for testing purposes I put them in. I do plan to put in a full set of 95/96's once I am convinced the unit is problem free.
    So I separated the pre from the amp ,hooked it up to my dbt and it powers up fine. I measured for DC on both channels and they are bang on.
    The next step will be to reconnect the pre and see what happens.
    Any suggestions? It was during the adjustment of the tone controls that lead to the short.
     
  15. Fhamre

    Fhamre Super Member

    I hooked up a seperate pre amp to confirm the amp section was functioning correctly and all went well.
    Then I switched the amp to connect the pre and hooked up to the dbt tested the unit.
    All is working well. I also put the tone controls through their paces to try and replicate when the unit shorted. So far it appears to be working fine.
    Hmm.
     
  16. Fhamre

    Fhamre Super Member

    Still trying to determine what caused the pair of outputs to short out.
     
  17. The Fuxtor

    The Fuxtor AK Subscriber Subscriber

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    Never fun when these units have some type of phantom issue thats off the wall.....Keep looking! Do you use an o-scope?
     
  18. slimecity

    slimecity Super Member

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    Are you confident that the buyer didn't cause an "idiot mistake" like shorting out speaker wires?

    Did the outputs only go in one channel?

    I guess you have already checked for any oscillation with a scope? What about some issue like the buyer introducing a new element to the system, like a new TT or cart, which may have started oscillation/feedback issues that then cascaded somehow into transistor failure?
     
    Oldsansui441 likes this.
  19. Fhamre

    Fhamre Super Member

    Yes the out puts blew in one channel.
    Well the owner did have a turntable pre amp hooked up through aux at the time. But he uses it on other units without a problem. He was adjusting the tone controls while on moderate volume when the outputs went.
     
  20. restorer-john

    restorer-john Super Member

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    So did the buyer, or you make that shipping crate? It's very nice. :)

    I have an awesome 600x600x700mm timber crate made for me by the boys in our Sydney furniture factory (back in the day), that I had 3 pieces of Pioneer Urushi Reference gear shipped up 900km to me, then I used it again, by sending the empty crate and packaging 2000km south to Adelaide and then shipping it back 2000km to me, with three Sony ES pieces in it. All it cost me was a carton of Corona for the boys at the Qld freight depot. It was 85kg total with gear in it. Not even a speck of damage on anything when it's wrapped, packed and put in a crate with a screw on lid.
     
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