Question about Mitsubishi VS-50705 50" Rear Projection Television

1 Answer

Have no service manual--but suspect convergence output amps--now power issue

The problem began with a rolling picture broken by several horizontal bars for half an hour and then the roll would cease and as long as the unit was left on, the picture would remain steady. Suspect vertical control circuit and convergence output amplifier STK's. No bad solder joints or broken trace are apparent. wiggle and tap tests yield no changes. Signal from pin 7 on IC802 is ringing with all sorts of overlapping signals. This had me believing the problem was a bad solder joint or crack in the trace...possibly bad amp. I wanted to test using manual circuit adjustment however the unit would not permit entry in to Service Adjustment Mode despite setting Direct key entry mode to "On". Since beginning to troubleshoot the signal and main boards, the unit suddenly ceased to complete powering on. Have STBY 12V on board and the fuses are intact....130V and 18V + HV is present for an instant and it would seem a protection circuit kills the process before it can complete.

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  • Noel Rusnell
    Noel Rusnell Jul 30, 2008

    will try that and post back here...i suspected a protection circuit...but will try convergence yokes. You wouldn't happen to have SAMS for the VS 50705 VZ7 chassis? I have service manual for VS 50707 VZ8 chassis...trade?

  • Noel Rusnell
    Noel Rusnell Jul 31, 2008

    unplugging yokes at DY makes no difference. I should have specified more clearly: During the process of troubleshooting the main board, line fuse blew and then after replacing the fuse, the unit exhibited the symptoms mentioned from here on: Self diag codes do not
    come up currently due to power not completely coming on Prior to
    failure to power "On" the self-diag code came up as 12--normal no
    errors and >>
    a. Option menu; press MENU 1270

    b. Service menu; press MENU 1257.
    <the menus prior to the latest issue of complete power "On" failure, and
    i was at that time able to set Direct key entry mode to "On" but the
    REW, Play, FWD, etc keys failed to bring up service mode settings.

    The
    most pressing issue currently is the failure to completely Power "On".
    Upon resolving this, I then need to address the rolling vertical
    blanking issue. I also do not have the service manual for this
    unit...only VS50507, VZ8 chassis, so I am winging this one.

    Unit will power on only long
    enough (500µs) upon pressing power button either with remote or on
    front panel to give 18V, 130V and then K903 de-energizes and kills HV
    and 16V, etc. before any diag codes can display. here's the sequence: set clicks on, Horiz.
    Output energizes, flyback energizes, 1/2 second later K903 clicks off
    and set goes back to "off" more on checks, bypassing Q971 will force the on/off relay K903 to energize and remain energized. SW12 and SW130 result, but nothing else comes on...no crt, audio, tuner, etc.

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  • Mitsubishi Master
  • 8,617 Answers

Its most likely the convergence ICs that are shutting the set down. Have you tried unplugging the convergence yokes to see if the set will then power up?

Posted on Jul 30, 2008

  • Sonny Berry
    Sonny Berry Jul 30, 2008

    No I sure dont have the manual for that model. Sorry

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PO Box 442
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360-642-4993
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VZ7 chassis problem began with rolling picture and now protection kills power on process


Good Day, NT-Services;

You may a vertical problem but I think it's not the vertical output amp. The problem should be in the voltages feed the vertical circuit. I have had cocern many times, so try this first:
1. VERTICAL ROLLING, VERTICAL BLANKING BAR LOCKING IN THE MIDDLE OF THE PICTURE, ALSO MAY HAVE HORIZONTAL PULLING OR TEARING. CHECK C2C52 10 UFD @ 50 V OFF THE BASE OF Q2C51 ON THE SIGNAL PCB. 2. CHECK C2P05 100 UFD 16 V OFF PIN 3 OF IC2P01 AND IC2P01 PART # 270P466020 (9-VOLT REGULATOR). BOTH ARE ON THE SIGNAL PCB.

Replace these caps no matter how they check.

2. Shuts down; may be intermittent, self-diagnosis ERROR 23 or 24. Check solder connections at connector "DY" on the yokes. Or/and check C411 2200 UFD 35V AND C412 10UFD 50V, both located on the main PCB.

3. Service adjustment codes:
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b. Service menu; press MENU 1257.

I hope this was helpful. Good day, big IRISH.

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