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
    I bought CR820 from ebay. It powered up, relay clicked but there was no sound at all to start with.

    I Replaced most of capacitors which looked swollen, De-oxidised the fuses, contacts on controls, opened up and cleaned relay. Checked all 4 transistors on side , they are fine, cleaned and re-seated them.

    After all this work when I switch it on, its dead. I have checked that there is 240v at primary but I can not measure any voltage at secondary, or should I say I do not know how to.

    There are 2 red + black wire and 2 orange + blue wire. I have measured AC Voltage between red & Black, Orange & Blue but it just reads zero. All these wires are wound to a metal contact on board not soldered. Should I remove the wires before measuring?

    Can anyone please guide me how to proceed next? Should I just purchase a new transformer?
     

     

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  2. RT Fan

    RT Fan AK Subscriber Subscriber

    Messages:
    3,008
    Location:
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    Welcome to AK, I have an 820 and think it is worth saving. Here is a link to HIFI Engine from which you can download the schematics and service manual. I am sure soemone will be along shortly to help with your question. Good luck and welcome aboard.
    https://www.hifiengine.com/manual_library/yamaha/cr-820.shtml
     
  3. avionic

    avionic " Black Knights " Subscriber

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    Location:
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    @sajjad amer

    Update your progress and I'll help you here.
     
  4. avionic

    avionic " Black Knights " Subscriber

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    Check both speaker A and B -- make sure you have the correct speaker button selected.
     
  5. sajjad amer

    sajjad amer Active Member

    Messages:
    205
    Location:
    Lincolnshire, United Kingdom
    Update so far, I managed to restore power it was a broken wire on main power board. Relay clicks intermittently. 7/10 times it does not click, if i keep pressing the power button I do hear a click. But again no sound at speaker terminals. I have measured voltages at orange coloured coils, one coil measures 0 volt and other 19 v. I have removed 4 transistors on side and checked, all 4 check perfect.
    I have double checked and correct channel is selected. Please help how to investigate it next , thank you
     
  6. avionic

    avionic " Black Knights " Subscriber

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    Does your FM meter and LED's appear to be functioning correctly ? While trying to tune in a station ?
     

     

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  7. sajjad amer

    sajjad amer Active Member

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    yes, FM, AM lights come on, when I move the tuning dial signal meters move and even stereo light comes on as well
     
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  8. avionic

    avionic " Black Knights " Subscriber

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    40,048
    Location:
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    May still have and power supply issue.
     
  9. avionic

    avionic " Black Knights " Subscriber

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    Stand-by.............................
     
  10. avionic

    avionic " Black Knights " Subscriber

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    Need to see if your pre-amplier circuits are getting the correct supply power.
     
  11. sajjad amer

    sajjad amer Active Member

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    205
    Location:
    Lincolnshire, United Kingdom
    Happy to do measurements as per your instructions, please advise.
     

     

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  12. avionic

    avionic " Black Knights " Subscriber

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    Measure the collector voltage of TR609 and TR610. We are looking for the same 30 vdc (ballpark) at both collectors.
     
  13. avionic

    avionic " Black Knights " Subscriber

    Messages:
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    Location:
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    Also measure the collector voltages of all of the output transistors
    These transistors.
     
  14. sajjad amer

    sajjad amer Active Member

    Messages:
    205
    Location:
    Lincolnshire, United Kingdom
    Its 43v at out put transistors and 28v at TR609, I cannot find TR610, still looking
     
  15. avionic

    avionic " Black Knights " Subscriber

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    Are all of your incandescent lamps illuminate ? Did you replace C804 ? (33µf/16vdc) Probably a violet colored cap with reddish print...
     
  16. avionic

    avionic " Black Knights " Subscriber

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    + and - 43vdc ?

    Collectors of TR609 and 610 should be the same polarity.
     

     

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  17. sajjad amer

    sajjad amer Active Member

    Messages:
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    Location:
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    None of the lamps glow, I am waiting delivery of new lamps. I did not replace the 33uf 16v cap as I did not have it in stock at time of recap.
     
  18. sajjad amer

    sajjad amer Active Member

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    Location:
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    from front to back
    -43, +43, -43, +43
     
  19. avionic

    avionic " Black Knights " Subscriber

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    Location:
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    Is your audio muting button disengaged ?
     
  20. avionic

    avionic " Black Knights " Subscriber

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    Location:
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    Its probably whats messing up your protect relay intermittent issue. Replace with a Nichicon PW or equivalent low impedance cap.
     

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