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Help wanted with a Sony PS-33 (direct drive turntable)

Discussion in 'Repairing Electronics' started by john1, Jun 7, 2017.

  1. john1

    john1 Active Member

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    Hi,

    I'm trying to fix a direct drive tuntable unit, 45 and 33 rpm.
    Its a Sony unit, PS-T33. Any help or advice would be welcome.

    The speed control unit runs at 13 to 14 volts,
    the motor appears to have windings in a square arrangement.

    It has a speed sensor round the inner edge of the turntable,
    which i guess is compared to the mains frequency,
    but i dont really know.

    The turntable doesnt rotate, even if you help it manually.

    I have downloaded the manual, which includes a schematic
    but no explanation of how it operates.

    Any help appreciated, John :)
     
  2. crutschow

    crutschow Well-Known Member Most Helpful Member

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    Have you checked for power at the appropriate points?

    For example here's the power input as taken from the schematic:

    Look for about 10Vac voltage at the transformer outputs and +12.5Vdc and -13.5Vdc at the bridge outputs.

    If you have that then just keep looking down the chain to see if all the other voltages look okay.

    upload_2017-6-7_21-24-35.png
     
  3. GromTag

    GromTag Active Member

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    Not familiar with these models, Sanyo was the last I've been through and that was models from the 80's - early 90's, and some had strobo to control fine tuning of the selected motor speed. Still have a turn top for one.... somewhere.

    If not an geared motor assembly then the turn top shaft may have frozen via lack of oil. The documentation shows the motor to be a magnetic type servo, the shaft can seize at the motor bearing at the square motor base plate if the record turn top disc itself is not in contact with the base (top deck) of the rest of the table (dragging) it can act quite like a brake boot when in contact. The PDF for documentation is 9.43Mb. So a link is provided if needed.

    A link to the documentation is https://freeservicemanuals.info/en/servicemanuals/viewmanual/Sony/PST33/

    The Type a PS-T33 is the acquirement of the datasheet. Year models under similar production model number may differ even with same number of PS-T33, use caution. Link to data provided if not known, and as you seem to have the components apart this could help with part identification and reassemble.

    The PDF Zoom feature would be required to view the info in a readable sense. If a PDF viewer is available for the above overall.
     
  4. dave

    Dave New Member

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  5. KeepItSimpleStupid

    KeepItSimpleStupid Well-Known Member Most Helpful Member

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    It appears to be a complex beast. You do have a block diagram. As suggested, make sure the power supplies are working first. The neon light, the LEDS.

    Then I'd concentrate on Ic-2 pin 5 and pin #6 and the C-E voltage across Q8. You don't want Q8 to be turned on.

    What I don't like is the voltage ratings of C9 and C10. I think all sorts of failures are possible because of the lack of any clamping on the line voltage.

    Your turntable has the strobe for the user to measure the speed, but the absolute speed is governed by the adjustments.

    I worked on two pieces of instrumentation that have interesting case histories:

    1) A thermocouple scanner that was used near a high power IR temperature controlled heater. The schematic showed the voltage regulator was unpopulated on the board. I chose the clamping fix.

    2) A multi-channel analyzer which kept blowing $1000.00 USD boards. When i told the manufacturer that they had no surge suppression in their $5000 unit, they claimed they specify 120 VAC 60 Hz. Surges don't meet that requirement.

    A piece of audio equipment was a repair return in a shop and I eventually got it to fix for the shop. An audio IC was tun too close to the maximum voltage so it kept popping.
     
  6. john1

    john1 Active Member

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    Hi,

    Yes, i know its been a while, but i'm still working on this thing
    just a case of as and when.

    Crutschow
    ---------
    I will be double checking those voltages you mentioned, which i
    had looked at before i had seen a diagram.

    GromTag
    -------
    No its not geared, its direct drive, the motor spindle is the
    turntable spindle, and its not jammed or frozen, you can help it
    turn by hand when its supposed to, but it doesnt even try to run.
    Yet sometimes it gives a little jerk when its switched on,
    so at least one of the windings is responding a bit.
    Haven't got that link to work yet, still trying.

    KeepItSimpleStupid
    ------------------
    Yes it does seem overly complicated for a record turntable,
    i will check out those connections on IC-2, and Q8.

    I had not noticed how close C9 and C10 were up to the limit,
    I will check them out too, and maybe up them to a bit of a
    higher working voltage. I agree with you they should be a
    little higher rated.

    My regards to you all, and i will try to get this sorted.
    Cheers, John. MotorSupplyCirc.jpg
     

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