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CR-2020 Service Bulletin Guidance

Discussion in 'Yamaha' started by Hi Fi Fan, Jul 30, 2018.

  1. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    Hi everyone, new member here.

    I just purchased a working CR-2020. I opened it up yesterday to clean pots, etc. and check to see if the Service Bulletins have been performed. I have modest to average electronic repair skills.

    The power switch was shorted, I rebuilt it and added the jumper as advised in the SB. Works great now.

    I inspected the electrolytic cap board to see if that SB work has been done. There is some scorching on the board so part locations are difficult to read. There are a few components raised up off the board and the soldering for these parts appears non-factory. Can anyone tell from the attached photos whether the subject SB components have already been replaced?

    http://audiokarma.org/forums/index.php?media/img_1787.15983/
    http://audiokarma.org/forums/index.php?media/img_1790.15984/

    The 2 transistors on the power supply board referenced in the SB appear to me to be original based on the part number. I touched up the solder points and am wondering if these transistors should to be replaced as a matter of course or can I just add larger heat sinks? A quick check online suggested that these parts may have been obsoleted.

    http://audiokarma.org/forums/index.php?media/img_1796.15985/

    Thanks is advance.
     
    Last edited: Jul 30, 2018

     

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  2. avionic

    avionic " Black Knights " Subscriber

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    Welcome to AK... Does not look like SB's have been complied with. The resistors in question look OEM to me.
     
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  3. avionic

    avionic " Black Knights " Subscriber

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    Those have been obsolete for a long time... 5-10 years or more..
     
    Last edited: Jul 30, 2018
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  4. avionic

    avionic " Black Knights " Subscriber

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    Last edited: Jul 30, 2018
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  5. avionic

    avionic " Black Knights " Subscriber

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  6. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    Thanks a lot for the help everyone, I appreciate it!!!

    Do any of the capacitors need to be discharged before doing the SBs?

    Thank you!
     
    Last edited: Jul 30, 2018

     

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  7. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    "These are no longer available so either use a TIP41C or 2SD613."

    Awesome, is either TIP41C or 2SD613 preferred?

    Thank you.
     
  8. avionic

    avionic " Black Knights " Subscriber

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    Which ever is easiest to obtain. . The 2SD613 is probably obsolete as well.
     
  9. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    Thank you!
     
  10. avionic

    avionic " Black Knights " Subscriber

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    Probably wouldn't hurt to check the two bigg'ns.
     
  11. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    My thoughts exactly!

    Newbie here, do I just short one pin to ground and then recheck voltage?

    Thank you.
     

     

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  12. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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  13. Oilmaster

    Oilmaster Drillers go deeper Subscriber

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    For your absorption regarding the SB resistors :
    http://audiokarma.org/forums/index....-41vdc-on-outputs.787761/page-3#post-10992603

    KSD526 (available with most suppliers) is a decent sub for TR712/715
    Having adequate cooling for these trannies is typical service topic #2 for this unit.
    Some inspiration here:
    http://audiokarma.org/forums/index....toration-guidance.798122/page-6#post-11128538

    Those purple sleeve capacitor(s) should really be replaced; they age very badly, and cause all kind of issues such as a non-engaging relay.
    Talking about it, the relay would be typically replaced (by Omron MY2-DC12) as well when your donw there.
     
  14. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    Thanks I will check those links out, appreciate the help!
     
  15. avionic

    avionic " Black Knights " Subscriber

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  16. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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  17. avionic

    avionic " Black Knights " Subscriber

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    Last edited: Jul 30, 2018
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  18. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    Thank you, ordering parts today!
     
  19. Oilmaster

    Oilmaster Drillers go deeper Subscriber

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    What really really really surprises me is that your unit is seemingly originally missing fusible resistor FR803 !
    That is where that black wire jumper is on your board.

    IMG_1796mku.jpg

    I think 'originally' as your PCB has not even the resistor value printed on it as it usually does.

    DSC06765mku.jpg

    That is a first off!
    What is the serial number of the unit?
     
  20. Hi Fi Fan

    Hi Fi Fan AK Subscriber Subscriber

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    Thanks a lot. I noticed that too while I was inspecting these boards, "hmm, weird jumper wire here." Is it advisable to add a resistor there? If so, is it a 10ohm 220ma as shown?

    Serial is 02922, see attached.

    Without going nuts as my skills are limited are there any other "should do" parts replacements on these boards for reliability? I found another thread that suggested another 4 capacitors:

    http://audiokarma.org/forums/index.php?threads/yamaha-cr-2020-faulty-no-sound-sb-mods.291232/

    "In addition to the service bulletin repair parts as listed in the first post, i also replaced the two 1000mfd/50 capacitors with 63v/1000mfd capacitors per merrylanders advice and two 1000pf/100v ceramic capacitors behind the SD234 transistors."

    Thank you!
     

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    Last edited: Aug 1, 2018

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