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RCA 64" Projection TV

Discussion in 'Electronic Repair' started by Chris F., Dec 11, 2005.

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  1. Chris F.

    Chris F. Guest

    I hate servicing projection sets, but agreed to this one simply because
    business is so slow these days. Right away it's obvious I will need some
    help:
    When I first tried the set, pushing power causes the set to cycle on and off
    very rapidly (for as long as power is held down). I went through the power
    supply and tried replacing some caps; now, pushing power starts the set for
    a half second and it shuts right down - and will not try to start again
    until the set is unplugged for a minute. Testing has ruled out HV shutdown.
    The first thing I intend to replace is the EEPROM. While I wait for that
    to be ordered, can you give me any other advice? The customer said the set
    would also go to a black-and-white picture once in a while, and turning it
    off for a few minutes would correct the problem (at least for a few more
    minutes). So I suspect there may be other problems waiting to be found, once
    the set is brought back to running condition. Or is that perhaps a fault of
    the EEPROM as well??
     
  2. James Sweet

    James Sweet Guest


    Does the EEPROM commonly fail on these? I don't think I've ever come
    across a bad EEPROM in a TV, not to say it doesn't happen, but it
    certainly wouldn't be my first suspect unless it's a known issue.
     
  3. Guest

    With the exception of the tuner ground causing failure of the eeprom
    data on the direct view ctc177 series, I have never seen an eeprom
    failure in an RPTV set.

    There is little real technical information in the OP to garner any kind
    of help.
    It might be best for the OP to post information like a trained,
    equipped, and qualified technician would.
     
  4. Sky

    Sky Guest

    Unhook the high voltage splitter input from the flyback, & if the unit comes
    on with filiaments, you have it. If this fails to get it going, the flyback
    may be
    bad, especially if nothing else is bad. The red wire next to the flyback can
    also make it look like the flyback itself is bad. Look for CRT coolant leaks
    ....many problems with these with leaks, & a lot more. Is it "squealing"
    while
    it's trying to start? You have a short, if so. Check the horizontal output,
    pincushion correction circuit, & convergence power supply. Hope this
    helps. EEPROM highly unlikely at fault, unless someone was at the unit,
    or if the tuner was really bad...solder connections, & left to long. Sky.
     
  5. Chris F.

    Chris F. Guest

    I neglected to mention the chassis # - it is a CTC-169PT
    No evidence of coolant leakes at all, and I've tried to power it with the
    yokes & flyback lead disconnected. As I said before, I ruled out HV shutdown
    by disconnecting that lead to the TA8680 IC.
    I've replaced many bad EEPROMS on the CTC-175 series....
    One other thing worth noting; with a VOM connected across the B+ supply, I
    noticed something odd; when the set is plugged in, instead of going directly
    to 150 volts or so, it goes to about 100 and slowly ramps up to 150 within
    3 - 5 seconds. Maybe this is normal, I'm not sure.
     
  6. Guest

    150 volts is too high.
    Do a google groups search for all the pertitent ctc169 information.
    15V run diode problem, all the power supply capacitors, standby power
    supply voltages etc.

    Set will still go into protect shutdown if the hv splitter is bad due
    to the power supply load. Pull the hv lead out of the hv splitter and
    check inside for carbon problems, typical additional failure after the
    smps was running too high as it is right now.

    You also cannot run the ctc169 with the yoke leads disconnected, that
    too will cause immediate shutdown.
     
  7. Chris F.

    Chris F. Guest

    Set fixed - I replaced the three NTE 588 diodes in the switching power
    supply and everything seems great. Funny though, since the diodes checked OK
    on a DMM. Oh well now I know that for next time.
    Thanks to all for the advice.
     
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