Another Pionner sx 1250 repair

Discussion in 'Pioneer Audio' started by Joe Stem, Mar 9, 2017.

  1. Joe Stem

    Joe Stem Member

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    was having a hard time getting the Strap desoldered but i got it... it toook two days of patience but i got it without damaging the traces... found a replacement on Ebay for $17.00 but im on hold until it gets here. the rectifier checked at ~450 on the DMM for both diode posts
     

     

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  2. rcs16

    rcs16 AK Subscriber Subscriber

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    Pretty hefty price for a dual diode, there were other cost effect solutions such as using 1/2 of a bridge diode or dual diodes in a TO-220 and adding a small heatsink. The dual diode approach could have made a much higher performance rectifier using fast recovery diodes, which product much less switching noise.
     
  3. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    It is but it will continue in an original configuration. No modification required. An easy replacement. No fuss no Muss. I can't think of any more phases.
    That's worth the extra cost.
     
  4. Joe Stem

    Joe Stem Member

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    i thought about replacing the whole board for 60 then i don't have to solder anything BUT that defeats the purpose of doing REAL reapair work
     
  5. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    The eBay seller has the listing for two pieces. He also sells the inverse S5151's. I wonder if he would, or why doesn't sell the Rectifier as a pair?
    It might be to late to see if he would sell a set instead or two of the same diode.
     
  6. Joe Stem

    Joe Stem Member

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    Im gonna ask that Question... im having some Paypal issues at the moment... i was wondering the same thing why not sell as a pair,,,
     

     

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  7. Joe Stem

    Joe Stem Member

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    All though if you re do both boards you would need 2 of each so maybe thats his thoughts... who knows
     
  8. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    Not all sets use two sets.
    Good luck.
     
  9. Joe Stem

    Joe Stem Member

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    Ok... Update... I got paypal Straightened out and got the part ordered... i ordered 2 S5151R Diodes for $17.50 will be here on or before Apr. 3. Will be back then to continue the repairs...
     
  10. Joe Stem

    Joe Stem Member

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    Ok everyone I'm back... Got my New S5151 diodes... installed one in the spot on board 106... @zebulon1 where do we go from here...
     
  11. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    Put it back together leaving the amps disconnected.
    Power up on the DBT and measure the voltages at the terminals on the large caps.
    The only issue might be the AC voltage from the transformer but I think you checked that.
    I should work but be on your toes.
     
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  12. Joe Stem

    Joe Stem Member

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    will report back in a bit
     
  13. Joe Stem

    Joe Stem Member

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    @zebulon1 After re installing the diode, i powered up on DBT and 1 cap still gets Hot... the new cap in the same position as the one that blew...

    here are the voltage readings
    with unit standing on its rear
    looking at caps terminals
    Top Left - +47.3VDC
    Bottom Left - +43.6VDC
    Top Right (Hot Cap) - -40.4VDC
    Bottom Right - +43.5

    Also tested voltages on board 106
    Pin 1 - -39.2
    Pin2 - +39.2
    Pin3 - GND
    Pin 4 - +0.4
    Pin 5 - +0.4
    Pin 6 - +49.0
    Pin 7 - +13.0
    Pin 8 - +13.1
    Pin 9 - +4.6
    Pin 10 - +23
    Pin 11 - 50.2
    Pin 12 - GND
    Pin 13 - -50.9
    Pin 14 - -23.2
    Pin 15 - -52.7
     
  14. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    Joe,
    This predicament is some fault of mine.
    The diode you replaced is located on the Stabilizer board (AWR-106) correct?
    I didn't want to get the 1250 I ave here out but this deal made it happen.
    That circuit is a simple one. It powers the outputs. That's all it does.
    Well the one thing I couldn't remember is how the wiring is connected.
    The point I'm trying to get to:
    There must be an output shorted on that right side.
    Did you look at the right amp board for any visual clues? A damaged driver stage could of caused the failed output.
    The four outputs should be checked.
    Sorry for the runaround.
    Were on the right track.
     
  15. Joe Stem

    Joe Stem Member

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    yes the cap that is getting hot is connected directly to an output transistor, would that be the one... the amp boards look fine visually... are my voltages checking correctly now? i noticed some pretty sizeable differences in the before and after readings
     
  16. Joe Stem

    Joe Stem Member

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    how do i perform the checks on the outputs?
     

     

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  17. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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  18. Joe Stem

    Joe Stem Member

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    @zebulon1 would it be wise to just replace all output Transistors... and have the part Numbers changed from what is in the manual is 2sd555-r and 2sb600-r is that correct
     
  19. zebulon1

    zebulon1 Building a new bench. Finally! Subscriber

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    I wanted to mention to check the wiring harness around the heatsink when removing the outputs.
    The replacement outputs are the On-Semi which are supper nice but you should consider replacing the left side to match the channels.
    MJ21196/95's
     
  20. tsd71

    tsd71 RIP Tom Petty

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