CR-1000 humming from both channels

Discussion in 'Yamaha' started by sssboa, Mar 17, 2017.

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  1. sssboa

    sssboa Active Member

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    357
    Hi

    I opened my CR-1000, measured some voltages, replaced 4 caps on preamplifier (Filter Amp) from 10uF63v to 10uF35v. Had to resolder a few cables on the filter amp as well. I turned the receiver on and I have humming on both channels, irrespective of volume setting, doesn't change with volume at all.
    I measured voltage again and now I have 62V from power supply to the filter amp (through tone amp). Before it was 52V.
    I never touched the power supply. How is it possible that changing caps on filter amp (preamplifier) and resoldering some wires that snapped off in the process caused different voltage from power supply?
    When I decouple preamp the humming gets like 5 times less loud but still is there.

    If you remember after doing similar maintenance on preamp of my other CR-1000 (also changing some caps on the small preamp boards) I lost completely one channel, still haven't solved it either. That's why I opened the other Yammy, to compare the voltages, that were the same btw ( also for the lost channel) until the humming issue started. So the not humming Yammy (but without one channel) still has 52v from power supply to filter amp, the humming one 62v.
    Strange, before, I did full recap with pre-emptive :) change of many transistors in one go on CR-1000 and I never had a major problem like now doing small things :(
     
    Last edited: Mar 17, 2017
  2. sssboa

    sssboa Active Member

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    357
    Before someone asks I just measured fusistors on power board and all are spot on.
     
  3. avionic

    avionic " Black Knights" Subscriber

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    Your not having very good luck with CR-1000's
     
  4. Nashou66

    Nashou66 AK Subscriber Subscriber

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    Why did you go down in Voltage from 63 volt caps to 35 volt? Better get the right voltage capacitors in there before you break something else.

    nashou
     
  5. sssboa

    sssboa Active Member

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    357
    35v are original as per schematics on this board: 2x 10uF35v and 2x 100uF10v. Those 10uF63v had exceptionally bad ESR, around 1.2ohm vs 0.30 ohm for 35v, I use GP caps.
     
  6. avionic

    avionic " Black Knights" Subscriber

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    Did they look OEM like the others ?
     
  7. avionic

    avionic " Black Knights" Subscriber

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    Schematic diagrams are frequently " wrong "...
     
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  8. avionic

    avionic " Black Knights" Subscriber

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    Always go with what was installed.. Unless its obvious as hell. That they are not OEM.
     
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  9. mbz

    mbz Well-Known Member

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    808
    Location:
    Melbourne, Victoria
    I'm not familiar with the CR-1000 layout so I'll probably stuff
    up here.

    Firstly the filter amp caps.
    10uf/35V (c605,6??).
    The working voltage at this point is ABOUT 27V for a nominal +B=50V.
    So the cap 35V rating should be OK. However under fault conditions
    (TR601) the cap may see the full +B. So I like the 63V rating.

    10uf/35V (C609, 610). This is probably a similiar scenario, under
    normal operation the 35V rating is fine however under fault conditions
    it is significantly exceeded, however I don't see it.

    Also I don't see the 10uf/35V cap as the source of either the hum or
    abnormal +B=62V.

    I would agree with others that if the original caps looked OEM then I
    would stick with those ratings, it's too expensive to update the
    service manual. Both the CA-800 and CA-1000 SM's have 10uf/35V caps
    in these position, but that means squat. My note taking at this time
    was poor, I replaced them with 10uf/50V probably because they were
    at hand.

    +B=62V.
    TR801,802 are candidates, to test. I assume you checked FR801,3.
    You could check the -50V supply on the Power/Relay Board (-50V or -62V?)

    Hum both channels.
    My basic understanding is that if the noise/hum does not increase with
    volume then it occurs after the volume control so candidates are tone
    and filter boards.

    If the CR-1000 is anything like the CA-800/1000 then the filter board
    is a real PITA. You may have stressed some of the connections. Suggest
    checking the +B and E connections on the filter board, also reflow the
    solder. As always, it could be a dry solder joint that has been disturbed
    by the cap replacement. This applies to all boards handled to replace
    the filter board caps.
     
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  10. sssboa

    sssboa Active Member

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    357
    Update: one is dead now. I am gonna send them to a repair shop nev
    Hi Thx for this.
    I replaced the transistors on power supply you mention some time ago to modern equivalences. I measured all FRs, they are ok.
    I am a noob tho. All is new to me.
    I measure the voltages by touching black probe of multimeter to the case and the red one to the point I want to measure. Is it a right way?

    BTW, just ordered "electronics for dummies", hope won't be too advanced for me :)
     
    Last edited: Mar 18, 2017
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  11. avionic

    avionic " Black Knights" Subscriber

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    Does the service manuals parts list state 35
    Yes thats correct.
     
  12. sssboa

    sssboa Active Member

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    357
    Service manual states 35v. I swapped the caps back to 63v but no change.
     
    Last edited: Mar 18, 2017
  13. sssboa

    sssboa Active Member

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    357
    -50v is -62v, 33 is 40 if I remember well. Consistent difference by around 10v.
     
  14. mbz

    mbz Well-Known Member

    Messages:
    808
    Location:
    Melbourne, Victoria
    Both +ve and -ve supplies are too hot. Does the CR have a voltage selector? Is it
    correctly set? What is the voltage stamped/pronted on the back? Maybe measure
    the AC voltage between the 2 yellow wires on the relay board.
     
  15. sssboa

    sssboa Active Member

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    357
    It has been set to 240v forever.
     
  16. mbz

    mbz Well-Known Member

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    808
    Location:
    Melbourne, Victoria
    What country are you in, Aust? and is the supply 240V?
    Are you saying there is a switch and it is set to 240V?
    Sorry, just need to be clear.
     
  17. sssboa

    sssboa Active Member

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    357
    UK, 240v in the wall
    Not Austria :)
     
  18. sssboa

    sssboa Active Member

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    357
    Another novice question.
    Is everything that goes out of the transformer and into the boards, DC? Especually the 2 red wires that go through fuses on top of the upper deck and then down into the power supply pcb.
     
  19. mbz

    mbz Well-Known Member

    Messages:
    808
    Location:
    Melbourne, Victoria
    Can you measure the AC voltage on the 2 yellow wires? Is it possible to do the same
    on your other unit for comparison? Need to track down why the supply voltages are too high.
     
  20. mbz

    mbz Well-Known Member

    Messages:
    808
    Location:
    Melbourne, Victoria
    Everything that comes out of the transformer is AC, red wires included.
    The AC is "converted" to DC by the rectifier/diode bridge, eg D801,2 and D806, 7 ...
     

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