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CR-2020 Repair Advice

Discussion in 'Yamaha' started by sajjad amer, Mar 29, 2018.

  1. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Service bulletins are to replace 2 each 22 Ω/3.25 watt and 2 each 33Ω/3.25 watt. As well as rewire the convience AC plug. And replace the power supply pass transistors. I've done all three mods many many times.
     

     

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  2. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
     
  3. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Those two were not part of the service bulletin.

    And personally I would not have used 5 watt resistors for the service bulletin. There is very limited space where the 22Ω & 33Ω ( service bulletin) reside and the 22 Ω's are suppose to be fusible as well.
    http://sportsbil.com/yamaha/cr-2020-servbull1.pdf
    http://sportsbil.com/yamaha/cr-2020-servbull2.pdf
    http://sportsbil.com/yamaha/cr-2020-servbull3.pdf
     
    Last edited: Apr 6, 2018
    sajjad amer likes this.
  4. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
  5. Goldie99

    Goldie99 Well-Known Member

    Messages:
    771
    Location:
    The original Boston, UK
    Sorry avionic - I most certainly didn't mean to question your experience in any way, quite the opposite - I was simply confused by the earlier reference to 22R max 1/2W (post #3), I took that to refer to what was needed for FR801 & FR802, not what was being replaced.... and subsequently 'lost the plot'.... good job there's a Dr. in the house :)
     
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  6. sajjad amer

    sajjad amer Active Member

    Messages:
    255
    Location:
    Lincolnshire, United Kingdom
    I have finally got the protection circuit board recapped. Good news is relay is clicking, but still there is no sound. The relay is clicking immediately when I flick the switch, it is not clicking like it should. I have checked capacitors twice, they are in right polarity. Where have I gone wrong can you please guide me? Thanks
     

     

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  7. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Look over your solder connections for solder bridging. The relay driver transistor may be shorted E-C.(TR702)
     
    Last edited: Apr 7, 2018
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  8. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Check your coupler switch position on the rear panel as well as your speaker selector switch on the front panel.
     
  9. sajjad amer

    sajjad amer Active Member

    Messages:
    255
    Location:
    Lincolnshire, United Kingdom
    spot on, cleared the solder bridge and now back to square 1, lights are back on, signal quality meter has gone back to zero, but no relay click and no sound.
     
  10. sajjad amer

    sajjad amer Active Member

    Messages:
    255
    Location:
    Lincolnshire, United Kingdom
    Coupler switch is set to on, speaker selector switch is set to A and wires are plugged into A.
     
  11. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Need to check the output of each amplifier for the presents of DC voltage.
     

     

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  12. sajjad amer

    sajjad amer Active Member

    Messages:
    255
    Location:
    Lincolnshire, United Kingdom
    I have checked and readings are as follows
    Speaker selector switch to A-- and measuring voltages on speaker A terminals L+R = 0 volts
    However
    When I put the probes on speaker B or C it reads -28 mV
    And
    When I select speaker selector switch to B or C the reading goes back to zero
     
  13. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Can't use the speaker terminals if the relay is not clicking. Have to measure the output on each amplifier board before the protect relay.
     
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  14. sajjad amer

    sajjad amer Active Member

    Messages:
    255
    Location:
    Lincolnshire, United Kingdom
    image.jpg Do I need to measure it at orange and blue wire ?
     
  15. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Top edge of each board has a lug marked O and E. O is output and E is ground. Measure the voltage across these two teminals.

    Do not short these two terminals together or you will destroy your output transistors.
     
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  16. sajjad amer

    sajjad amer Active Member

    Messages:
    255
    Location:
    Lincolnshire, United Kingdom
    Left Board measures 6.66mV and Right Board is 8.81mv
     

     

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  17. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Thats a good sign. .So that means the problem is in the protect circuit or the protect circuits power supply. Not enough DC at the output to trigger the protect circuit.
     
    zaibatsu and sajjad amer like this.
  18. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    Need to check TR702 and TR706 out of circuit prefered.
     
  19. sajjad amer

    sajjad amer Active Member

    Messages:
    255
    Location:
    Lincolnshire, United Kingdom
    @avionic you are the man. In the following thread you mentioned capacitor was installed incorrectly and I had the same issue.
    http://audiokarma.org/forums/index.php?threads/yamaha-cr-2020-help.663359/page-2
    Now when I switch on the receiver relay clicks after 10 or so seconds (quite long time). BUT still no sound.
    I removed each and every transistor off the relay board and checked with transistor checker, they all check fine. I have also Re soldered the whole board. IMG_0920.JPG IMG_0920.JPG IMG_0919.JPG IMG_0920.JPG IMG_0919.JPG IMG_0918.JPG IMG_0923.JPG IMG_0923.JPG IMG_0927.JPG IMG_0931.JPG IMG_0920.JPG IMG_0919.JPG IMG_0918.JPG IMG_0923.JPG IMG_0923.JPG IMG_0927.JPG IMG_0931.JPG I get no reading neither between TP1 and 0 nor 0 and E on both amplifier boards.
     
  20. avionic

    avionic " Black Knights " Subscriber

    Messages:
    42,768
    Location:
    Fort Dodge, Iowa
    What position is the coupler switch on the rear panel in ? Speaker select switch in the proper position?
    Mute switch disabled ?
     
    Last edited: Apr 15, 2018

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