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Sony TC-WR770/870

Discussion in 'Troubleshooting and Repair' started by Darryl, Sep 13, 2016.

  1. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Are you on fb messenger maybe link up by video

    I have -7.5v and +7.5v tested that with black test lead on chassis and found my 7.5v links and they are ok


    I forgot to say ed thanks for your continued support with this issue i do check on here now and then
     
    Last edited by a moderator: Oct 30, 2018
  2. Robisan

    Robisan

    1
    0
    Oct 30, 2018
    Hi all, just having the same problem with my TC-WR870 gone completely dead apart from a momentary flash of the light units behind the tape decks when turning it on. Have hunted thru all the capacitors [hoping that's all it was] but they are all looking ok. Checked the power transformer and all outputs are in spec, chased all the way to the main board plug to confirm the tranny tranfer board and the cables were ok. Done the usual uninformed process of tapping anything I can tap without causing a short or electrocuting myself all to no effect. Nothing works: no display, no opening of the cassette doors, no funny smells so nothing's fried, So, Daryl, I wonder if you managed to solve your issue and can provide a hint or two as a result? I really want to fix this machine: it's one of a kind genuine built in Japan and absolutely immaculate...
     
  3. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Still working on it but if you email me at [email protected] and i will email you a service manual.
    But your right these units are rare now
     
  4. Darryl

    Darryl

    15
    1
    Sep 13, 2016
     

    Attached Files:

  5. Darryl

    Darryl

    15
    1
    Sep 13, 2016
     
  6. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Im tempted to remove R700, R703 and R704 and replace with new as the problem lies with one of these.
    I blew unit number 2 last week as 1 strand of wire shorted on the back of left hand capstan motor and a small plume of smoke came from around these 3 fusible resistors
     
  7. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Have a look at these photos
     
  8. 73's de Edd

    73's de Edd

    2,573
    1,053
    Aug 21, 2015
    Sir Darryl . . . . .

    Your problem should be that your shorting out of the motor, caused R700 . . . which is a 0.1 ohm 1/4 w film resistor . . . being used as a fusible resistor . . . . to open up, and is now leaving the ground leg of the D702 full wave bridge rectifier to be floating above ground.

    Therefore . . . . . no 11VDC is getting to your motor circuitry to run it.

    Wire in / clip in, a voltmeter across C704 to be able to read the emitter of Q702 regulator transistor .
    Then power up and then take the new resistor and just make a 1-2 second, brushing against connection to see if an expected 11 VDC shows up . . . OR . . . if an unregulated 20VDC shows up.

    If 11VDC appears you are in business to wire in the new R700 and fully try out the deck.

    IF . . .20VDC . . . .expect Q702 or Q 703 to having crunched Collector to Emitter . . . and needing replacement.

    Thaaaaaaaaaasit . . . . .

    73's de Edd
    ......................


    The next time when I go to the ATM, and just after the money comes out, I'm going to
    jump up and down, then flail my arms wildly about flashing the money and finally, shout out, for all to hear.

    "I won!" "I won!" . . . its the 3rd time this week ! ! ! "


    . . . . . . Copywight 2018 . . . . . by Elmer Fudd. . . . . . All wights wesewved. !.
     
    Richard9025 and Darryl like this.
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