PSU not starting

Discussion in 'VuPlus Duo Hardware troubles and Repair support.' started by tomeek.p, Aug 17, 2018.

  1. tomeek.p

    tomeek.p Member

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    I have problem with PSU. I replaced the F101 fuse because the time is broken. On IC1 on the leg of the Vcc I had a short to ground, IC1 replaced the short circuit gave way. But I still have a short to ground on the Q4 transistor.

    The f101 fuse continues to burn.
     
  2. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    In the evening I'm be able to take a look of it because right now I'm not on my work location.
    But I have take some looks on my clone Psu pics and could not find the Q4 location, maybe you have it about the original Psu?
     
  3. tomeek.p

    tomeek.p Member

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    Yes, this is orginal psu.
    IMG_20180817_161640.jpg
    IMG_20180817_161705.jpg
    IMG_20180817_161740.jpg
     
  4. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Ah, okay in that case I will examine it today, in the evening.
     
  5. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Okay, the ohm values Q4, ground taken from the C1 cap ground side..
    pin 1 = 11.6 ohms
    pin 2 uploading 5.05M to higher due the D5 and caps c5 etc., if it's shorted, check the IC2
    pin 3 ground due the sr1

    f101 fuse continues to burn..
    Replace/check the brd1 bridge rectifier and D1, but also if the IC2 has issues, the fuse will burn.
    Check also the C4 and D4, D5, remove them to see if the short circuit resolves.
     
  6. tomeek.p

    tomeek.p Member

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    Diodes and cap is ok. The diodes had a value of about 520. Remove the IC2 and the short circuit to the ground disappeared.

    @EDIT
    There are no short circuits, but the IC2 fuse has broken again. I found a tight Q2 tracker. Pins 3 and 2 have a short circuit, that is base and collector.
     
    Last edited: Aug 18, 2018
  7. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Q2
    Pin 1 to 2, 128.8 ohm
    Pin 1 to 3, 127.0 ohm
    Pin 2 to 3, 3.9 ohm.
    When measured it between the ground hot side and pin 2 and 3, M ohm down, up to 136.0 kohm

    Be aware that even if the measurement of brd1 bridge rectifier may fine, it can still be leaking when it's powered.
    Better is to replace it, just to be sure.
     
  8. tomeek.p

    tomeek.p Member

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    Q2
    Pin 1 to 2, 160.1 ohm
    Pin 1 to 3, 161.9 ohm
    Pin 2 to 3, 2.3 ohm.

    When measured it between the ground hot side and pin 2 and 3, M ohm down, up to 2.6 kohm
     
  9. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    Okay, that seems to me fine.
    In any case, since the c5 has some white glue on it on your picture, check these, it should be 46.8 between it.

    Snap7.jpg
     
  10. tomeek.p

    tomeek.p Member

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    Ok I find broken element SR1. R13 - 970 kohm and D4 (looks strange)- 970 kohm 560points. In SR3 have 0 ohm.

    IMG_20180827_103140.jpg

    Thermister TH1 also is broken.
    C5 46,4
     
    Last edited: Aug 27, 2018
  11. Johnny B.

    Johnny B. Technical Support Staff Member Moderator

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    As far as I measure it then the sr1 in a zero ohm resistor, th1 gives 50 ohm, r13 100k, and thus the d4 should give also this value.
    measured d4 between a hotzone ground spot to the d4 loads up to 1.6m ohm to higher.
    SR3 not found.