Restoration Help Yamaha CR-820

Discussion in 'Yamaha' started by sajjad amer, Feb 8, 2018.

  1. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    TR610 Collector is 28.5, just disengaged the Mute button, still no output at speakers, I am afraid.
     
  2. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    ok, I am expecting delivery from digikey and will report back , everything else so far has passed your inspection ?
     
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    I was kinda hoping it was a missing the 30 volt ( 28.5v) power supply voltage.:idea:
     
  4. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    Took out the cap from circuit and measured
    ESR =10,
    V Loss, 6.8,
    C=17.40
     
  5. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    Which Transistors specifically drive the relay? Should I check them just in case ?
     
  6. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    Do you own a set of headphones ?
     
  7. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    Just check the solder connection on TR805. I you wish..TR804 and 805 are the drive transistors. The pass transistor TR805 normally runs very warm and over time fatigues the solder connections.
     
  8. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    yes, just checked with headphones as well, static when inserting the jack in A and B. Nil else. Has Rec Out Selector any bearing on the sound output, I have kept both selectors on Aux, and using laptop sound card as source at AUX.
     
  9. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    junk it.
    That violet cap is bad 9 times out of 10.
     
  10. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    ok, will replace the cap and report back. I have 47uf, 50v in my kit, can I use it momentarily to check if every thing works? I have reflowed the solder on TR805
     
  11. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    Check or reflow your balance and volume control solder connections.
     
  12. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    I will, do it now and report back
     
  13. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    It will alter the delay time,but should work.
     
  14. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    Replaced the cap as suggested, now the relay does not click at all, despite multiple on/off cycles
     
  15. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    I guess it won't work then...Have to wait til you get the proper cap.
     
  16. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    ok, will report back with outcome, thank you ever so much for your time, I appreciate it . \regards Sajjad
     
  17. ConradH

    ConradH Addicted Member

    Messages:
    7,395
    Location:
    Canandaigua, NY
    Or, the protection is working correctly. More times than I care to admit, when I've thought a protection circuit might be messed up, it was doing it's job and protecting me from something else that was wrong.
     
  18. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    Also find R725 and R726.. One end of each of those two resistors should have + 28-30vdc and the other end should be .68 vdc ..
     
  19. sajjad amer

    sajjad amer Member

    Messages:
    55
    Location:
    Lincolnshire, United Kingdom
    The relay circuit is actually doing its job. @ConardH you are right.
    When the radio is properly tuned in, upon switching it on, I hear FM radio for a sec and then relay clicks and silence !!!
    If Radio is not tuned in I hear a Loud Thud and Silence !!
    @avionic
    R725 - one end is 28.3 other end is 0.62
    R726 - one end is 28.3 other end is 0.73
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
    38,105
    Location:
    Fort Dodge, Iowa
    OK...find R802 and R803 ( 47 KΩ ) in the protect circuit. Check for DC voltage on both ends of each resistor. Should be close to zero volts ( + or - 50 mv or less) on either end.

    The voltage your looking at is the DC offset of each amplifier circuit.
     
    Last edited: Feb 10, 2018

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