Pioneer Sx1010 Repair - Diodes

Discussion in 'Pioneer Audio' started by 70smidfiguy, Dec 16, 2018.

  1. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Hello,

    Im working a Pioneer SX 1010 where the relay circuit is not working.

    The power supply board looks pretty rough so I'm replacing some sketchy components.

    Most I have except the W320 Zeners.

    I have have some 1N4757A' in stock, would they work as a sub?

    Thanks.
     

     

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  2. tsd71

    tsd71 RIP Tom Petty

    Messages:
    2,617
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    I would use................WZ-320= 512-1N5257B 33v zener

    1N4757 is a 51v zener
     
  3. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    I'm wondering if I have an incorrect copy of the service manual.

    Im getting 35V across 15 on the power supply board where it says it should be 24V.

    All other voltage ok, + or - 1V or so.

    GBC-FASHADSKTP 2018-12-17 10.47.06 PM .jpg
     
  4. markthefixer

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

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    IF pin 15 was having the rated current pulled through it (28 mA) then it would be at 24v.
    There are multiple circuits pulling from pin 15, the equalizer amp and the control amp.
     
  5. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    These are the power supply board voltages I currently have:

    15 ..... 34v
    14 ..... 57.2v
    13 ..... 36.3v
    11 ......-23.4v
    10 ......-53.7v
    9 ........-12.4v
    8 ........12.96v
     
  6. markthefixer

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

    Messages:
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    Location:
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    Those power supply regulated voltages are OK.

    pin 15 MAY be a symptom, the 24v is not pulling enough current - i.e. something ain't running.
    pin 15 runs the phono preamp and control amp. Neither would easily inspire the protect TO protect (by not pulling in the relay)..

    Need you to measure and post the bare metal chassis ground referenced voltages you find on these pins:

    AWM-062 protection board
    pin 1 audio input, good would be dc millivolts, bad can go up to over 30v
    pin 2 -13.6v dc
    pin 3 audio input, good would be dc millivolts, bad can go up to over 30v
    pin 4 ground zero ohms to bare metal chassis
    pin 5 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v
    pin 6 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v
    pin 7 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v
    pin 8 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v
    pin 9 +36.5v dc with relay open, 10v with relay pulled in
    pin 10 +36.5v dc
    pin 11 +36.5v dc
    pin 12 7.5v AC <<<<<<<<<<<<<<< SWITCH YOUR METER OVER TO READ AC VOLTAGES!!!!!!!!!

    Then if you find pin 12 HAS the 7/5v AC on it, then you need to read the DC voltage found on the junction point of C5 (minus terminal) R34 and R25 : it should be -5.1 volts and it is crucial.
     
    Last edited: Dec 19, 2018

     

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  7. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    AWM-062 protection board
    pin 1 audio input, good would be dc millivolts, bad can go up to over 30v (-36.5v)
    pin 2 -13.6v dc (-12.32V)
    pin 3 audio input, good would be dc millivolts, bad can go up to over 30v (-34.8v)
    pin 4 ground zero ohms to bare metal chassis (0)
    pin 5 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v (-36.7v)
    pin 6 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v (-36.7v)
    pin 7 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v (-35V)
    pin 8 audio over-current protection input, good would be dc millivolts, bad can go up to over 30v (-35v)
    pin 9 +36.5v dc with relay open, 10v with relay pulled in (36.7v)
    pin 10 +36.5v dc (36.7v)
    pin 11 +36.5v dc (36.7v)
    pin 12 7.5v AC <<<<<<<<<<<<<<< SWITCH YOUR METER OVER TO READ AC VOLTAGES!!!!!!!!! (7.54vAC)
     
  8. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Sorry, probably should mention that output transistors are/were NOT installed while the above readings were done
     
  9. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    The junction of C5 (-) to R24 and R25 are (-3.88v)
     
  10. markthefixer

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

    Messages:
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    Well, I think it is dawning upon you that the amplifiers are intimately concerned with the protection and MUST be in tip top shape before attempting to power up the amplifier circuits.

    There is a method to connect in some temporary resistors to test the DC balance of the amplifier circuits and their readiness to be connected to output transistors SAFELY!!!!

    There are two threads where this method is discussed and used, both are technically involved.

    The SX-1010 power amp circuit's driver transistor stages are set up in a way (non-interconnected) that allow tremendously BAD fault voltage excursions for the output transistor base drives.
    This requires additional effort to make things safer (for the equipment) while troubleshooting - to avoid additional damage.
     
  11. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    All Output transistors re-installed. DBT failing.

    'You can check the diodes by removing them but that could be a pain in the rear. It still could have a short in the amplifier board. Remove pins 15 and 16 on the fuse board and re-lift the resistors on the PS board R11 and R12"

    I saw this in another thread. When I pulled 15 &16 from the fuse board, the DBT dimmed and all the display lights came on.

    Thoughts?
     

     

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  12. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    A shorted output.
    An output in the wrong position.
    An output installed so that the collector is shorted to the heatsink.
     
  13. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Thanks and Interesting.

    The sockets for the output transistors are very poor (plastic starting to crack, forks pop up).

    Will also try and source replacements :(

    Can you see any issue with me running your resistor test off the amp boards to confirm issue with output transistors? (Found that in an old thread)

    Remove the output tr's and tape off then connect large resistors to amp board for load. Test on DBT.

    Cheers
     
  14. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    I also have a couple of questions if you don't mind?

    1. What is "EchoWars 6 way diode test" (on each output transistor before installation)?
    2. Please advise on where to set the trimmer values on the driver boards when they have been replaced. (Also the output tr's are new as well)

    CMSI-HQ-RD01 12-21-2018 10.59.09 AM.jpg

    Thank you again for all of your help!
     
  15. markthefixer

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

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    http://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

    Pay close attention to post #11 in that thread and it's explicit examples of the six readings to be taken.

    now, for the replacement trim pots:

    For the sx-1010, the replacement DC offset adjust VR1 (2,200 ohms) at the EDGE of the PC board (the big red "1") should be set in the middle of it's range (which can be up to 25 turns!!), and then adjusted for 0.000v at pin 19 (and / or pin 20 right next to it on the SAME copper pad)

    For the sx-1010, the replacement idle current set VR2 (470 ohms) found in the CENTER of the PC board (the big red "2") should be set to a reading ACROSS the pot IN CIRCUIT of zero ohms. I say it this way because the terms clockwise and counter clockwise are woefully imprecise and can be affected by many many factors INCLUDING the internal wiring of the replacement pot and how it is installed.
    IF the setting of VR2 is the WRONG direction, maximum resistance could direct the circuit to provide an excessive (possibly even damaging) amount of current.

    As for installing the output transistors, NOT YET. Don't jump ahead - that's a cardinal sin. Be SURE the drive voltages for the bases of the output transistors are correct, and the amps are DC balanced. That means you should see about +0.6v at the pin 10 and -0.6v at the pin 13 with 0.000v at the pin 19 (or the pin 20)
     
    Last edited: Dec 21, 2018
    rcs16 likes this.
  16. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    On it, thank you!
     

     

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  17. 70smidfiguy

    70smidfiguy Active Member

    Messages:
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    Location:
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    "As for installing the output transistors, NOT YET. Don't jump ahead - that's a cardinal sin. Be SURE the drive voltages for the bases of the output transistors are correct, and the amps are DC balanced. That means you should see about +0.6v at the pin 10 and -0.6v at the pin 13 with 0.000v at the pin 19 (or the pin 20)"

    For clarity, for me to test the drive voltages and consequently the driver boards in their entirety, should I take the output transistors out, tape off the sockets and cables and add 250ohm 5-10W resistors for a dummy load, all on the DBT?

    Thanks
     
  18. markthefixer

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

    Messages:
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    Location:
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    yes

    In order to close the feedback loop and be sure that the amplifier IS running correctly.
     
  19. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Hi,

    Something seems wrong with my setup or reading as I'm getting around -29V on pin 19 to ground on DBT.
    See pics below, with the resistors in place the DBT does dim. (See bulb on left)

    20181227_233804.jpg 20181227_233908.jpg
     
  20. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Checked off DBT and both driver boards show -43.7v on pin19. Bulb Dims!
     

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