Repairing a Noah Schumacher-hacked up Sansui 9090

Discussion in 'Exclusively Sansui' started by EastPoint, Feb 9, 2019.

  1. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    Hi folks. I have a Sansui 9090 I am working on. The previous owner bought it from Noah Schumacher (of Hallo-Fi and Jahrgang Audio fame) as fully restored. It worked for a while then stopped working. He brought it back to Noah, who charged him to restore it again, but instead took 7 months to repair it. When the guy got it back it had a bunch of different lights and bent pots and he suspects that it's actually a different unit. Seriously.

    Anyway, it worked for a while and then stopped working again. So, now I have it.

    The 9090:
    Comes out of protection fine.
    Amp section works fine with the jumpers pulled.
    With the jumpers in, comes out of protection, but no sound and the FM tuning meters will not move at all. I am guessing no power to preamp/tuner sections.

    Here's what I have noticed as far as hackery goes:
    Rear AC fuseholder disconnected completely--no fuse in it and wires are cut. Unit still runs, wires appear to have been rerouted. This seems unsafe, right?
    Rear voltage selector was set at 100v, which seems bad. I changed it to 120v.
    The board with the relay has some badly damaged traces that were jumped.
    Relay and main caps are original, despite this being "restored" twice.

    I checked voltages coming out of the power transformer into the power supply and they appear to be good. I am guessing that prolonged operation set at 100v probably fried something in the power supply. Anything I should look at first?

    IMG_8685.JPG IMG_8693.JPG IMG_8694.JPG IMG_8697.JPG IMG_8698.JPG IMG_8700.JPG
     
    Last edited: Feb 9, 2019
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  2. Robisme

    Robisme Sansui Enthusiast Subscriber

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    What's the voltage on the tuner power supply?

    You can test it at the small post in front of the big transistor. The two white resistors are known to desolder themselves.

    Rob
     
  3. lbcgav

    lbcgav AK Subscriber Subscriber

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    Wow! I heard about this guy...sounds like he pulled the wool over a lot of people. I hope you can get it working.
     
  4. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    Sorry, thought I had attached pictures. They are there now. @Robisme, I'm assuming you're talking about that little board to the left of the tuner board. I see a big heat-sinked transistor and two big white resistors, but I don't see a small post there.

    IMG_8686.JPG
     
  5. DougBrewster

    DougBrewster AK Subscriber Subscriber

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    The small post is more like a pimple protruding through the surface of the board..,
     
  6. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    I still don’t see a post but I checked a bunch of connections on that little board and I’m getting zero volts everywhere except TR02 has 3.5v on the E side.

    TR01 has zero volts on all three pins.
     

     

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  7. ic-racer

    ic-racer Super Member

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    Hope you get it running. I don't own any Sansui or have any of the schematics so, just I'm following along to see what else you find that he botched.
     
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  8. Tom B

    Tom B AK Subscriber Subscriber

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    sounds like you are missing the 36V.. That 36v is used by many of the boards (Equalizer, Tome Amp, control am, and mic amp)
    Check F01 and F02 on the main power supply board 2546. The 36v is developed on that board, and then feeds to the equalizer board, and is routed from there to the small Regulator board used for the tuner (board 2431), and the other boards . There are 3 molex connectors plugged into the equalizer boar. Just make sure they are in correctly, in that one of them gets the 36v in from the power supply, and then feeds the 36v to the other boards.
     
  9. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    F01 and F02 both have 38 VAC on them. The fuses are good.

    I see four molex connectors on the EQ board. They all appear to be in fine.

    image.jpg
     
  10. Tom B

    Tom B AK Subscriber Subscriber

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    make sure you have the 36v on both sides of the fuses.

    Power supply board should have 36v on pin 15, and that same 36v should be on pin 34 of the equalizer board. (voltage in) Then the 36 v should be on pin 51 going out to the small requlator board to the left of the tuner board (pin 3) . The 36v then passes through the 2 white power resistors, and gets to the collector of the regulator transistor at about 18v dc. The metal heatsink should read 18v.
     
  11. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    I do have 36V on both sides of the fuses. Just a sec, I'll check the other stuff.
     

     

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  12. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    The heat sink has zero volts. The Eq board has around 0.75 vac on pin 34. Pin 51 has zero volts. Pin 15 has zero volts.
     
  13. Tom B

    Tom B AK Subscriber Subscriber

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    Once you get past the fuses, we are typically looking at DC. Make sure you have around 52v dc on the collector of TR02 on the main power supply board. You should have this. If not, the dual rectifier D01 is bad, or you have broken foil on the board underneath. 52V on the collector of TR02 (metal tab on top is the collector, or touch the screw holding the transistor to the heat sink if there is one.) means the rectifiers are good. Then if no 36v on pin 15 is probably an open transistor TR02. I would suggest though to check with an ohm meter pin 15 to ground with the power off, unit unplugged. If you have a short at pin 15, it can be any of those DC filter caps on the tone board, control amp, equalizer board etc. Hopefully not and its just a bad 2SD313. Another way to tell if TR02 is open is to check the voltage across the base and emitter connections (the far left and far right pins, in that the center pin is the collector. If there is more than 0.6v across B to E, then it is open. When testing look for another place to test B to E rather than at the transistor where the spacing is too close and there is danger that you can short 2 pins. Follow where the B and Emitter ctch runs go and find a place where it is safe to put you voltmeter leads. It is also possible that TR01, and or TR03 could be bad as well.
    Make sure as well that pin 18 is connected to ground, and look at the underside of that power supply board and make sure there aren't any broken connections or cracks in that board.
     
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  14. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    So I actually tried replacing the two KSC2383 transistors on the power supply board and it came back to life. Now I just have to retire the AC fuseholder back into the circuit.
     
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  15. Tom B

    Tom B AK Subscriber Subscriber

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    GREAT NEWS!!!
    I assume those 2 transistors you replaced were the TR01 and TR03 transistors on the main power supply board.

    If you are having issues with the dual LED (Flashing red when it first comes on, and then Green after timeout) check the wiring on the protect board. It looks like a wire for "15" is not actually soldered in, but that there is a black wire tack soldered to that circuit trace.
     
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  16. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    The dual LED works fine, actually. I just need to do some cosmetic stuff and it should be good to go.
     

     

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  17. Tom B

    Tom B AK Subscriber Subscriber

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    Sounds good. Now that you got it working on the cheap, you need to treat yourself to one of those killer Prime Rib plates at Wards House of Prime. ( I used to spend time there in Milwaukee a few years ago on a consulting gig, while I was still working. I worked in a place on Michigan St right off the river. In fact one of my standby favorites was the "Swinging Door". They had great sandwiches.
     
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  18. EastPoint

    EastPoint Factory Code No. 4200 Subscriber

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    Thanks Tom. I've got a few local favorites as well. Quick question: I need a replacement relay for this thing, since apparently Noah didn't feel the need to replace it as part of his "restoration." Do you know what the Mouser number is for the relay? I thought it would be the same as the 9090DB relay, which I have here, but apparently it's not.

    [edit]: nevermind, I found it, it's the Omron MY4-02-DC24
     
  19. Tom B

    Tom B AK Subscriber Subscriber

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    correct its the 4 pole double throw pc board mount relay.
    The 9090DB uses a 3 pole double throw relay, where 2 poles are used for the speakers, and the 3rd pole is used for the led switching from flashing red to Green
     
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