Yamaha CR 620

Discussion in 'Yamaha' started by Fridge, Oct 31, 2017.

  1. Fridge

    Fridge New Member

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    Recapping and cleaning up an old Cr 620. All good, just noticed that 2 transistors on Main Circuit Board are Getting very hot. Signs of slight board burn around the heat sink. TR802, 803. CHecked Diodes and are good. Idle current is good as well. Is it normal for these transistors to get very hot? If not what ideas on what may be the trouble spots? By the way with new caps and cleaning this unit sounds very good. Thanks
     
  2. avionic

    avionic " Black Knights " Subscriber

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    Yes. Thats why they have heatsinks.;)
     
  3. Fridge

    Fridge New Member

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    19
    Location:
    North Carolina
    Thank you. .
     
    Last edited: Oct 31, 2017
  4. Fridge

    Fridge New Member

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    19
    Location:
    North Carolina
    Hey avionic, I also am cleaning up a CR 440. It sounds great too, but I can't seem to get any reception on the tuner. It is very week and sounds like some sort of short going on in this section...any suggestions to help with this issue? BTW, I can sut my stove off and cook eggs and onions on that heat sink:rockon:
     
  5. avionic

    avionic " Black Knights " Subscriber

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    If you have a service manual check your bias/idle current adjustment.
     
  6. avionic

    avionic " Black Knights " Subscriber

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    Are you using any sort of antenna ?
     
  7. Fridge

    Fridge New Member

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    Location:
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    I used a Dipole antenna, made no difference at all. The signal meter barely moves. Idle current is set to spec on service manual. All other inputs work and sound good?
     
  8. avionic

    avionic " Black Knights " Subscriber

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    What impedance are your speakers ?
     
  9. avionic

    avionic " Black Knights " Subscriber

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    Hows your superheterodyne alignment skills ?
     
  10. Fridge

    Fridge New Member

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    I have it hooked up to a pair of Minimus as my bench speakers..about the alignment, there is a first time for everythin. I am not afraid to give it a shot!
     
  11. avionic

    avionic " Black Knights " Subscriber

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    I'm betting you don't have the test gear to do the alignment properly. ie FM signal generator , oscilloscope , frequency counter or distortion analyzer.
     
  12. Fridge

    Fridge New Member

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    Location:
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    I would not take that bet! Ha. I thought about getting that stuff, then after a short thought, I thought not, due to I would not have a clue what to do with it. That gear is expensive even used stuff on auctions gets pricey. I don't think the unit is worth sending off.
     
  13. Fridge

    Fridge New Member

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    19
    Location:
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    Well, I dropped my screwdriver on the front end board and bam! I have perfect reception! Sadly it is after I poked around the trim pots and now I have a hum in the tuner section as I increase volume and I knocked the dial gear loose and broke the string! 1 step forward 3 back...its ok I will just keep playing..avionic
     
  14. avionic

    avionic " Black Knights " Subscriber

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    The service manual usually has a dial string diagram.
     
  15. avionic

    avionic " Black Knights " Subscriber

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  16. Fridge

    Fridge New Member

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    thanks for the link,,,,more fun to have!
     
  17. Fridge

    Fridge New Member

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    Location:
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    must have been a solder bridge or something similar that I loosened when I dropped the screwdriver. I was about to get PO'd and tear the unit up for parts.
     
  18. avionic

    avionic " Black Knights " Subscriber

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    Fun..Right.. Not my favorite thing to do.
     

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