Question about Mitsubishi VS-50705 50" Rear Projection Television

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VZ7 chassis problem began with rolling picture and now protection kills power on process

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

    Hi, there, I should have specified more clearly: 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 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 unless you can provide one....perhaps trade?

    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. set clicks on, Horiz. Output energizes, flyback energizes, 1/2 second later K903 clicks off and set goes back to "off"


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  • Master
  • 927 Answers

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:
a. Option menu; press MENU 1270
b. Service menu; press MENU 1257.

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

Posted on Jul 30, 2008

  • MICHAEL MULLINS Jul 31, 2008

    Good Day, NT-Services;
    If tries to turn and no error codes? Check IC700 pin 20 (AV off) for 0 VOLTS DC. If high, check for leaky D980 Part # 264P045040 on the main PCB.

    But I would suspect the caps previously mentioned and the vertical output IC. Try the caps and the IC first. ( CHECK THE CAPS AROUND THE 9 VOLT REGULATOR)

    Good Luck, big IRISH.









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