Issue with Pioneer SX 1280 on AFCI circuit

Discussion in 'Pioneer Audio' started by micaiahm, May 14, 2017.

  1. markthefixer

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

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    Please post the numbers on the transistors q1 and q2.

    bout time we stopped assuming anything.
     
  2. DerekR

    DerekR New Member

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    Pin 3 is low, which makes me think either the PA3004 isn't outputting enough voltage (it's drive circuit is dying) which means Q2 isn't switching in completely, or the base-emitter junction of Q2 is degraded and it's bias voltage is lower than it should be. I would pull Q2 and see if pin 3 gives a solid 0.7V.
     
  3. markthefixer

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

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    The thing is that this 0.3v reading could be a meter artifact, as the circuit drops the relay immediately.
    The only way that 0.3v is believable is if the unit continues with the relay PULLED IN.

    Realistically 0.6 to 0.7v is needed before any current begins to flow in the transistor collector to emitter.
     
  4. DerekR

    DerekR New Member

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    I'd thought he said the relay was pulling in for about 6 seconds; I'd think would be enough settling time for a DMM to take a solid reading. My thought was that if Q2 base-emitter junction was fried, it could have a lower bias voltage and be intermittently switching in and out. I'd be curious if he were to pull Q2 and measure pin 3 if he saw a steady reading or not.

    If it continues to drop in and out, then maybe it would be easier to determine what part of the circuit is causing the protection.
     
  5. micaiahm

    micaiahm AK Subscriber Subscriber

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    As requested:

    Q1 E 12.83V, C 0V, B 12.7V
    Q2 E 0V, C 75.2V, B 0V

    IMG_3138.jpg
     
    Last edited: May 30, 2017
  6. DerekR

    DerekR New Member

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    Not sure if he was looking for voltages or the part numbers marked on the IC body? 2SA733 and 2SC1438 according to the schematics, but who knows if they might have been replaced in the past?
     
  7. micaiahm

    micaiahm AK Subscriber Subscriber

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    That is what they are. 2SA733 and SC1438.
     
  8. markthefixer

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

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    Part Numbers. Those are Original Factory Transistors, go with ksa992 and ksc2690 if you have them.

    A lot of my original assumptions have been ruled invalid by this news.
    The "minty" status of either 1280 was no where near my standards for a minimal recap, no less a remanufacture, which is what I ASSumed was done.

    Plus I swallowed the initial assumptions of the first posts and ran with them UNskeptically.

    The six seconds was the delay between power on and the relay pulling in. AFTER which it would immediately drop out for another 6 seconds.
     
  9. micaiahm

    micaiahm AK Subscriber Subscriber

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    Mark,

    Thank you. As always, I appreciate your expert advice and valuable time. I wish the restoration and repair standards of all technichians were to a level of yours and some of the great guys on this forum. I am in no way to the level of you guys and thats why I thought to take this unit to someone who knew more than i did. But alas it seems I was screwed over by a local repair shop in the Hudson Valley. $800 six weeks ago. The "original" condition of this receiver was such that I purchased it and had it driven by a friend of mine from Michigan to me in NY.

    Your diagnosis now raises other concerns about workmanship, quality and what the heck else is wrong with this thing.

    I would love to have your level of restoration performed on this receiver because I really want to keep it. In fact on both 1280's that I have, but I only have space to keep one. If you have any recommendations I appreciate it.

    I have those transistors and I will change them out.

    Thanks again.
     
  10. micaiahm

    micaiahm AK Subscriber Subscriber

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    So I just finished changing out the Q1 and Q2 transistor. Same issue still exists.
    Q1 E12.83, C 0, B12.7; Q2 E0, C74.6, B0. So the only thing that changed was the voltage measurement of Q2 collector dropped .6V.
    PA 3004 1 12.8, 3 0, 4 0, 5 0, 6 -7.3, 7 .3VA, 8 engaged 2 disengaged 5.4
     
  11. markthefixer

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

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    Ok, some basic checks:
    (I checked the thread first to see if we already did this, because I was getting a strong sense of deja-vu )

    Is C1 (220uf 25v ) new or not?
    1. temporarily ground the collector of Q2, to make sure the relay will pull in and STAY in.
    2. Q1 gets disconnected, see if relay still cycles, leave disconnected for now.
    3. ground pin 4 temporarily, see if cycling stops.
     
  12. micaiahm

    micaiahm AK Subscriber Subscriber

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    Yes, C1 is new 220/50. From the board markings it is installed correctly.
    1. Did this and yes it does stay in.
    2. Did this and yes it still cycles.
    3. With Q1 removed, grounded pin 4 and it still cycles.

    Thanks again Mark for the help with this.
     
  13. petehall347

    petehall347 the brandy coffee man

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    am thinking exact voltages for all pins at pa 3004 need recording again .remembering pin 7 is AC volts .
     
  14. markthefixer

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

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    1. proves the relay drive circuit is capable, including the pull in capacitor.
    2. proves that there is no leakage or over current triggering input.
    3. proves it's NOT the DC voltage sensing input on pin 4.

    First, verify that AT pin 5 ground is zero ohms to the metal chassis.
    Then verify that there is zero ohms from ground to the minus terminal(s) of the timing capacitor(s) C16 & C3.

    Now, to contemplate what the PA3004 needs to operate:
    pin 1 needs a stable +13 volts to operate.
    pin 6 needs a stable -7 volts to operate, so D3 anode should stay at about -13v.
    pin 5 needs to be grounded.

    pin 4 stays grounded for now to simplify things

    there is no pin 2, and pin 3 is an output, with a new transistor. The LAST resort will be to disconnect that transistor.
    Pins 1, 4, 5 & 6 all should have a stable voltage and STAY stable

    That leaves pin 8 which is the timing capacitor. Check the ENTIRE trace connected to pin 8
    and the cap(s) for ANY indications of a short or any interference. To pin 7 especially, as well as D3 anode (that -13v point).

    And pin 7 which is an AC voltage input.
    I have reviewed the pin 7 readings in the thread, and think there needs to be a close examination here. The older posts have a slap-dash feeling.
    so I WANT AC voltage reading ( probably around 100 volts) of the board's pin 12. Then the PA3004's pin 7.
    Then set the meter to read DC, and read pin 7 again.

    On all these readings, watch them through several cycles of the relay, and see if there is any correlation between differences in readings to the cycling.
     
    Last edited: Jun 1, 2017
  15. micaiahm

    micaiahm AK Subscriber Subscriber

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    Now, to contemplate what the PA3004 needs to operate:
    pin 1 needs a stable +13 volts to operate. 12.8VDC
    pin 6 needs a stable -7 volts to operate, so D3 anode should stay at about -13v. -7.3VDC and -13VDC
    pin 5 needs to be grounded.

    pin 4 stays grounded for now to simplify things

    there is no pin 2, and pin 3 is an output, with a new transistor. The LAST resort will be to disconnect that transistor.
    Pins 1, 4, 5 & 6 all should have a stable voltage and STAY stable

    That leaves pin 8 which is the timing capacitor. Check the ENTIRE trace connected to pin 8
    and the cap(s) for ANY indications of a short or any interference. To pin 7 especially, as well as D3 anode (that -13v point). Did this and looks good. Pulled caps and re-installed to verify solder connection. See pic. Checked D3, and re-soldered as well.

    And pin 7 which is an AC voltage input.
    I have reviewed the pin 7 readings in the thread, and think there needs to be a close examination here. The older posts have a slap-dash feeling.

    so I WANT AC voltage reading ( probably around 100 volts) of the board's pin 12. Then the PA3004's pin 7.
    Then set the meter to read DC, and read pin 7 again.

    On all these readings, watch them through several cycles of the relay, and see if there is any correlation between differences in readings to the cycling.[/QUOTE]

    Board Pin 12 56.3VAC steady thru cycles.
    PA3004 Pin 7 .3VAC steady thru cycles.
    PA3004 Pin 7 .03VDC steady thru cycles.

    IMG_3141.jpg
     
  16. petehall347

    petehall347 the brandy coffee man

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    i would think pin 12 is about right .power supply pins 9 and 10 should confirm this . + -76v ...
     
  17. micaiahm

    micaiahm AK Subscriber Subscriber

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    Pin 10 76.4VDC
    Pin 9 -76.2VDC
     
  18. petehall347

    petehall347 the brandy coffee man

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    mark will figure this out . i am useless at voltage dividers .
    ac must be more than expected going off the ac after rectification . so pin 7 pa3004 should be a bit high rather than rather low .
    D3 anode is the odd thing here .
    have you got 2 multi-meters ? just a thought ..
    p.s sorry to butt in here mark . will leave you to it and follow . i am busy doing a 70th birthday at the moment . well its sleep time now ..16 channels to tune in tomorrow .
     
    Last edited: Jun 2, 2017
  19. markthefixer

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

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    resolder the chip except desolder pin 7 and stand up the pin so it is disconnected from the foil.

    Then check operation, pay attention to if the 6 second delay even happens and the relay tries to pull in.
    Remeasure the voltages, and for the divider bridge measure the foil that's isolated from pin 7.
    It looks right now like pin 7 has a problem, pulling too much current from the divider.

    You could check the resistors in the divider bridge.
    R10 is 1.8 meg ohms, R9 is 680k ohms.

    You can also set your meter on AC amps and measure the current being pulled from the divider bridge.
    connect the red dmm probe to the foil connecting r9 and r10, the black probe to pin 7.
     
  20. whoaru99

    whoaru99 Epic Member

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    Just curious....when you try it at home vs. away, is there other stuff connected to the receiver at home but not when trying it away?
     

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