Restoration Help Yamaha CR-820

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

  1. sajjad amer

    sajjad amer Active Member

    Messages:
    205
    Location:
    Lincolnshire, United Kingdom
    TR610 Collector is 28.5, just disengaged the Mute button, still no output at speakers, I am afraid.
     

     

    Please register to disable this ad.

  2. sajjad amer

    sajjad amer Active Member

    Messages:
    205
    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:
    40,048
    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 Active Member

    Messages:
    205
    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 Active Member

    Messages:
    205
    Location:
    Lincolnshire, United Kingdom
    Which Transistors specifically drive the relay? Should I check them just in case ?
     
  6. avionic

    avionic " Black Knights " Subscriber

    Messages:
    40,048
    Location:
    Fort Dodge, Iowa
    Do you own a set of headphones ?
     

     

    Please register to disable this ad.

  7. avionic

    avionic " Black Knights " Subscriber

    Messages:
    40,048
    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 Active Member

    Messages:
    205
    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:
    40,048
    Location:
    Fort Dodge, Iowa
    junk it.
    That violet cap is bad 9 times out of 10.
     
  10. sajjad amer

    sajjad amer Active Member

    Messages:
    205
    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:
    40,048
    Location:
    Fort Dodge, Iowa
    Check or reflow your balance and volume control solder connections.
     

     

    Please register to disable this ad.

  12. sajjad amer

    sajjad amer Active Member

    Messages:
    205
    Location:
    Lincolnshire, United Kingdom
    I will, do it now and report back
     
  13. avionic

    avionic " Black Knights " Subscriber

    Messages:
    40,048
    Location:
    Fort Dodge, Iowa
    It will alter the delay time,but should work.
     
  14. sajjad amer

    sajjad amer Active Member

    Messages:
    205
    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:
    40,048
    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 Active Member

    Messages:
    205
    Location:
    Lincolnshire, United Kingdom
    ok, will report back with outcome, thank you ever so much for your time, I appreciate it . \regards Sajjad
     

     

    Please register to disable this ad.

  17. ConradH

    ConradH Addicted Member

    Messages:
    7,597
    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:
    40,048
    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 Active Member

    Messages:
    205
    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:
    40,048
    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

Share This Page