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CR-620 Woes

Discussion in 'Yamaha' started by goldswimmerb, Nov 6, 2018.

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  1. petehall347

    petehall347 the brandy coffee man Subscriber

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    i like freeze spray to find them . it can get expensive though . that stuff aint cheap here .
     

     

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  2. goldswimmerb

    goldswimmerb Member

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    For freeze spray could I not just turn a can of compressed air upside down (you know the flourocarbon or whatever that is freezing)?
     
  3. avionic

    avionic " Black Knights " Subscriber

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  4. petehall347

    petehall347 the brandy coffee man Subscriber

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    i have used canned air upside down . it works but not as good as real freeze spray .
     
  5. goldswimmerb

    goldswimmerb Member

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    92
    I'll probably do that when we feel like opening it again. Right now, since the relay is switching again and the popping is intermittent at most now we'll probably wind up using it until that transistor gives up or the solder joint goes cold again
     
  6. petehall347

    petehall347 the brandy coffee man Subscriber

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    good luck with it ..
    p.s from my experience if it is a transistor or solder joint it wont fix itself . it will come back worse next time .
     

     

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  7. goldswimmerb

    goldswimmerb Member

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    The goal is to have it either die completely again honestly since I tend to work best when it's completely dead :p
     
  8. avionic

    avionic " Black Knights " Subscriber

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    :lurk:
     
  9. goldswimmerb

    goldswimmerb Member

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    Okay, so we're back at it, he finally had enough. We're getting 40v at the coil before the relay, I tested TR 703 And now we're seeing like E 10.5v B 50v C .4v
     
  10. avionic

    avionic " Black Knights " Subscriber

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    What is the base voltage of ..
    TR723 and 725 (output transistors) (For left channel)
    If its the right channel then...
    TR724 and 726 (output transistors)
     
    Last edited: Nov 8, 2018
  11. avionic

    avionic " Black Knights " Subscriber

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    Which channel? Which coil? L701 or L702?
     

     

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  12. ConradH

    ConradH Addicted Member

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    IMHO, all CR-620s have a capacitor problem unless otherwise proven. The (capacitor) problem is on the power board. The tuner board generally seems much better, save for two transistors. The first thing I'd do is change TR671 and 672. They're prone to noise and problems. Next, the relay circuit on this unit is remarkably confusing. Trying to understand it will cause brain failure. Just change out C809 in particular, and then C810-816. If that fixes it, replace the other caps on the power board at your leisure. If it doesn't, you need to get in there with a scope to see what's going on. BTW, when I'm too cheap to buy freeze mist, a bit of alcohol on a Q-Tip can often find bad small signal transistors by cooling them. Touch it to the tops. Just don't get alcohol on the board or it will short out.
     
    Last edited: Nov 8, 2018
  13. avionic

    avionic " Black Knights " Subscriber

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    Sure just start throwing parts at it.Maybe you will get lucky.Maybe....
     
  14. avionic

    avionic " Black Knights " Subscriber

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    If the problem was the PS it would effect both channels..
     
  15. goldswimmerb

    goldswimmerb Member

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    I believe 701, the same as earlier
     
  16. avionic

    avionic " Black Knights " Subscriber

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    Need to know what the base voltages are.
     

     

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  17. goldswimmerb

    goldswimmerb Member

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    So my board doesn't have labelling for those 4 transistors, however both of the of the 2SB531 are showing C- -37.2 B- -37.2 E- -38.1v
     
  18. avionic

    avionic " Black Knights " Subscriber

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    They are both located on the heatsink one is a 2SB531(TR725) and the other is a 2SD371(TR723)
     
  19. avionic

    avionic " Black Knights " Subscriber

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    If thats the case then both channels are f#k up. And you would have rail voltage( -38.1v)on both L701 and 702.
     
  20. goldswimmerb

    goldswimmerb Member

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    92
    Hmmm 701 shows 38v and 702 is a few mV still not really sure what's going on on, unless I'm an idiot and measuring wrong.
     

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