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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
    I was wondering if anybody could help me or point me in the right direction of the culprit which has killed full power supply in this tape deck.
    This is the 2nd unit ive had this happen.
    When you switch off the unit the capstan motors still run but at a reduced speed and also the rear tape lights are dim.
    There is a few resistor fuses on this board R700 R702 R703
    Can anybody help so i can restore full power to tge main board.

    Many Thanks
    Darryl.
     
  2. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Hello Darryl and welcome to EP.

    Sorry that no one has responded before now. Do you have a schematic?

    Chris
     
  3. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Hi chris yes i do.
    Ive done this to 2 machines now and i know i can fix it just knowing where the culprit is
    Just got the capstans running and tape window back light lit half power
     
  4. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Please post them.

    Chris
     
  5. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Hope this may help
     

    Attached Files:

  6. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Sorry, not with my old eyes. Even when I enlarge them they're just a blur.

    Perhaps a skilled member with younger eyes will chime in here.

    Chris
     
  7. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Questionable skill and no younger eyes here.
    It'd help if maybe you could make a larger pic of the power supply section schematic?
    Also, unless you see some heat damage with your referenced resistors, I'd be looking more at the capacitors
    as posing a potential problem here.
     
    CDRIVE likes this.
  8. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    Sounds like good advice from someone with questionable skills. I think you've graduated to skilled level. :)

    Chris
     
  9. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Maybe after another 46 years on the workbench, I'll move-up another peg to semi-skilled.
     
  10. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

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    May 8, 2012
    With any luck we'll get a larger photo with the area in question circled. With 46 years to play with I think the chances are good. :p

    Chris
     
  11. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir Darryl . . . . . . .

    Of your page 1 photo submitted . . . . 4th schematic page down.

    I was reading the schematic fine from A18---26 down to M18---26 and
    then you had just chopped off N-O-P 18 thru 26 where the vital info was
    located.

    Looking within the relevant portion that I can see . . . .
    As per any R700----702----703---- fuses? they would have to be low value
    fusible resistors and the R700 . . .etc series that I do see
    are being up in the 1K regions . . .therefore they are not being fusibles.
    There ARE F701 and F702 . . .1.6 A fuses.
    Do you have your + and - 7.5 vdc supplies and the + 5vdc supply ?


    Can you hit me with a conversation/message feature on this site to
    exchange E-mail addee's and I can extract and process the relevant
    schematic info to post ?

    73's de Edd
     
    Last edited: Sep 28, 2016
    Darryl likes this.
  12. shrtrnd

    shrtrnd

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    Jan 15, 2010
    Nuts. 73's de Edd must have a microfiche reader to have seen that.
     
  13. Darryl

    Darryl

    15
    1
    Sep 13, 2016
     
  14. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Hi Ed sorry for the late reply as ive just restumbled on this lost webpage again lol still trying to find the problem which i still have.
    i will try and get better picks.

    my email is [email protected]
     

    Attached Files:

  15. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    latest update is that this deck now has no power lol its lifeless and i need it to work again any help appreciated.
    i have found my copy of the service manual with circuit diagram.
     
  16. 73's de Edd

    73's de Edd

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    Aug 21, 2015
    Sir Daryl . . . . .

    Referencing to the simplified schematic at the very top, first . . . . . considering that you do not have a blown R704 fusible resistor . . . . . what supply voltages do you now have ? Finding those supply points on full schematic 2.
    OR confirm if you have AC output voltages at the transformer SECONDARY windings.

    Aside . . . .

    Ω test . . . . . testing Ω Ω Ω . . . . . . 1...Ω 2...Ω 3 . . .Ω ...testing.

    REFERENCE SCHEMATIC SNIPPET OF POWER SUPPLY . . . .

    [​IMG]

    73's de Edd
    .....
     
    Richard9025 likes this.
  17. Darryl

    Darryl

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    Sep 13, 2016
    What is the purpose of R700 and R703 and what component would kill power to the entire board
     
  18. 73's de Edd

    73's de Edd

    2,678
    1,085
    Aug 21, 2015
    Sir Daryl . . . . .

    WHERE? . . . . .you . . . .g o o o o o o o o o o o o o o ?

    latest update is that this deck now has no power lol its lifeless and i need it to work again any help appreciated.

    If that is the case, then take ohmmeter and test across the AC cords plug to see if you are reading tens of ohms resistance of the transformers primary winding.

    IF SO . . . . . . . . .


    Those are being fusible resistors that will that blow open circuit, in case of excessive .overload.
    R704 at the top is a given, in its wired installation.
    The lower R700 or R703's options are being incorporated in accordance to different -11,-12 or -13 board versions

    Starting all over again . . . . .

    Why don't you start by using a DVM and connect its black ground lead to the central ground buss that crosses the unit .
    THEN power up and check with DC metering to see if you find the bottom left corners MINUS 28 VDC supply being present.
    Then move up to check for the presence of the +5 and +11 VDC supplies..
    Then, move to the extreme right of the board and check for presence of the +7.5 VDC supply at the top left corner and then check the bottom right corner to see if the MINUS 7.5 VDC is present..

    Clue us in on what supply is missing . . . and we can then proceed.
    Sort of expecting your +5 and / or / + 11VDC to be missing.
    If that is the case . . .switch metering to AC mode and check for the presence of the ~15 VAC across power transformer terminals #11-13. Then stay on one lead and move one probe to #12 to see if it is reading ~ 1/2 the previous voltage being read.


    73's de Edd
    .....
     
    Last edited: Oct 19, 2018
    Richard9025 likes this.
  19. Darryl

    Darryl

    15
    1
    Sep 13, 2016
    Well ed im here working on it now.
    What actually happened i was changing ths left deck with a spare due to motor twitching even though timing marks are all correct but a couple of strands shorted on the 4 wires to motor but i did see a small flume of smoke from around those 3 pesky resistors
    Now if i put dtm on dc volts black lead on start of D701 and red lead at end of R704 i get a voltage of 2.65V.

    If i test either side of R703 i get 9.42V.
    But no voltage on R700 and R703 these 2 are in series i guess
     
  20. Darryl

    Darryl

    15
    1
    Sep 13, 2016
     
    73's de Edd likes this.
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