Pioneer Sx1010 Repair - Diodes

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

  1. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Regarding component replacements, my reference is the thread in AK but below is exactly what I used.

    AWH-032A:

    TR's:

    Q1=KSA992
    Q2=KSA992
    Q3=KSA992
    Q4=2SA1220
    Q5=KSC3503
    Q6=KSC3503
    Q7=KSC2690
    Q8=KSA1220
    Q9=KSA940
    Q10=KSC2703
    Q11=KSC1845
    Q12=KSA992

    DIODES:

    D7=1N4004
    D3=1N4004
    D1=1N4148
    D8=1N4004
    D4=1N4004
    D2=1N4148

    R29=.5ohm 5w Wirewound
    R30=.5ohm 5w Wirewound
    R31=.5ohm 5w Wirewound
    R32=.5ohm 5w Wirewound

    TRIMMERS:

    BOURNS 3386 H501
    BOURNS 3296 P202

    All electrolytic caps were replaced with same or higher voltage - same capacitance.

    Not replaced:
    Mylar/Ceramic capacitors
    Resistors (other than emitter resistors)
    ST-V3H Varistors
     

     

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  2. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Last thing, went back and check PS voltages again, only change was PIN 15 has dropped to about 27V, others are the same.
     
  3. markthefixer

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

    Messages:
    21,181
    Location:
    Bensenville,Illinois
    pin 15 voltage is dependent upon pin 15 current draw i.e. the "load"
    pin 15's load is the equalizer amp and the control amp. 28 mA

    There is another check to do, measure between pins 10 and ground, pin 13 and ground and from pin 10 TO pin 13 .
    Three readings for each channel, at minimum resistance of VR2 and three readings for each channel at MAXIMUM resistance of VR2.
    This is safe because there are no output transistors connected. That will tell us several things.

    Each amplifier channel is most likely "railed". The usual reason is an unrecoverable fault within the feedback loop.
    Since BOTH channels are independent except for the power supply, which HAS checked out ok, it has to be a common error.

    MY first step:
    recheck all transistor installations - perhaps post pictures so that fresh eyes can examine the installations.
     
  4. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Left ch

    10 - ground = -45v
    13 - ground = -48v
    10-13 = -2.6v

    Right ch

    Had a resistor burn for the 1st time R23 on the right ch 032 board !
     
  5. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Pictures:

    (Including burnt resistor)
     

    Attached Files:

  6. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    For the next guy, this is the way I received the receiver when I bought it!:
     

    Attached Files:

     

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  7. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    As a reminder, both channels still have the T-03 connectors and cables still soldered to the output boards with no transistors installed and the cables protected from shorting.

    Further, the pins 10 & 13 have 2 x 250ohm 10W resistors connected to pin 19.

    20190107_195409.jpg
     
  8. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Update: I removed both awh-032a from the receiver, completely as I wanted to redo all my checks and wiring to them.

    With both of them completely removed, the protection circuit clicked in. (Finally)

    I'm wondering if it is prudent to put one board in at a time and check or whether I need both in?

    Also noticed from other threads that I probably need a higher wattage bulb for my DBT as currently is a 60w bulb!
     
  9. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

    Messages:
    5,056
    Location:
    Las Vegas Nevada
    Double check the TO-126 transistors on the amp boards. They are very easy to put in wrong. The slim construction allows for the center leg to be bent forward instead of back.
     
  10. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Thanks for the response!!!!

    I have (honestly) triple checked these boards for orientation of tr's/diodes/caps.
    I have also compared against other pics in other threads and they look perfect.
    redid all solder pads, check continuity on all point to point connections.
    Compared to other pics I've seen, these boards look great. I have no pads lifting, no required jumpers.

    The only strange thing was that the high DC Offset was the same on both channels.

    So this should limit somewhat the permutations of the issues.

    The only parts not replaced on both boards are:

    The metal film resistors (tested)
    The carbon resistors (tested)
    The STV-3H varistors (not tested)

    The only other thing could be a chose the wrong replacement components but if so, so did a lot of other people because the replacements are all from these threads!

    I think what i will do next is put one board back in. Use the resistors across 10-13,19 and try the DBT test again. If dims, ill try and measure/adjust the DC offset again.

    Keep you informed.!
     
  11. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Ok, so after installing the R channel board again, installing the resistors across 10-13 to 19, DBT dims completely. I get a reading of about 12mv - 0mv from grnd to pin 19.

    I will try and install the L channel board now.
     

     

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  12. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    So far so good.
     
  13. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    DBT dims all the way.

    So with both boards in I get -28v on Pin 19 on R channel and 12V on pin 19 on the L channel. Adjusting VR1 has no effect on either Offset.

    Sigh!
     
  14. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
  15. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    I did put the old trimmers back in.
     
  16. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
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    I disconnected the L board again (shown as R above) Pin 19 dropped to 12mv-0mv (pops back and forth). Coincidentally VR1 does not change anything!
     

     

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  17. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Ok, I have checked/measured every setting possible and have this down to the two power amplifier boards.

    1. I have a component tester.
    2. I have checked the orientation of the tr's against boards themselves. (Several times!)

    What I did not realize was the variations of this board across 1010 revisions.

    Mine are LUGA (Written near emitter resistors) and AWH-032 A (written near the bottom of the board)

    I'm wondering if my component subs are correct.

    TR's:

    Q1=KSA992
    Q2=KSA992
    Q3=KSA992
    Q4=KSA1220
    Q5=KSC3503
    Q6=KSC3503
    Q7=KSC2690
    Q8=KSA1220
    Q9=KSA940
    Q10=KSC2703
    Q11=KSC1845
    Q12=KSA992

    DIODES:

    D7=1N4004
    D3=1N4004
    D1=1N4148
    D8=1N4004
    D4=1N4004
    D2=1N4148

    R29=.5ohm 5w Wirewound
    R30=.5ohm 5w Wirewound
    R31=.5ohm 5w Wirewound
    R32=.5ohm 5w Wirewound

    TRIMMERS:

    BOURNS 3386 H501
    BOURNS 3296 P202

    All electrolytic caps were replaced with same or higher voltage - same capacitance.

    Not replaced:
    Mylar/Ceramic capacitors
    Resistors (other than emitter resistors)
    ST-V3H Varistors

    The only other variable would be that I have used A992 from different vendors, are there variations on these?

    Thoughts? (I'm stuck, unless I try putting the old components back in)
     
  18. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
  19. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    Just an update:

    Rechecked all boards and found that I had used 2 x 1N4004 where they should have been 1N4148. Cleaned and tested all components.

    Reconnecting replacement output tr's and sockets to power amps boards tonight and will test on DBT.

    Fingers crossed.
     
  20. 70smidfiguy

    70smidfiguy Active Member

    Messages:
    122
    Location:
    British Columbia
    So after hooking everything up and turning on connected to DBT, bulb bright (Did not dim)

    Measuring:

    Amp Left Board:

    Pin 10 = 12.4v
    Pin 13 = -12.4v

    Amp Right Board:

    Pin 10 = 12.4v
    Pin 13 = -12.4v

    Black to Chassis

    Thoughts?
     

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