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Discussion in 'Electronic Repair' started by GregS, Apr 28, 2008.

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  1. GregS

    GregS Guest

    Working on a DLP projector, no light. I don't measure any voltage
    going to a lamp socket with lamp disconected. I looked for both AC and DC.
    Looks like there is a ahole board for the supply with OSRAM parts.
    Anything else to check ?

  2. James Sweet

    James Sweet Guest

    You could find the signal line that triggers the lamp driver to turn the
    lamp on and make sure it's changing states when the lamp should light.

    Be *very* careful probing the lamp sockets on these, a properly working
    driver will supply pulses of several kilovolts to ignite the arc in the
    lamp. You can easily fry your meter, or worse.

    The drivers are essentially switchmode power supplies configured to supply a
    constant current rather than a constant voltage. Standard SMPS
    troubleshooting applies, taking into account the greater than usual high
    voltage hazard.
  3. GregS

    GregS Guest

    I used an old analog meter. There is a LED lamp on indicatior on the top of
    the unit, and it does go on. Evn if I just had a bad lamp, I would imagine there would
    still be a clicking or visable arc around the lamp. $435 for a new lamp, wow.

  4. Jamie

    Jamie Guest

    Ha, Sounds like you have an RCA 61 inch? , that is what my DLP is. and
    it cost that much for a replacement lamp assembly..
    Your problem sounds like a ballast/driver problem.
  5. GregS

    GregS Guest

    Viewsonic, and I have to come up with a power cord.

  6. GregS

    GregS Guest

    I took the thing apart. One of the worst assemblies I have ever seen.
    Seems I can't find much info on Osram stuff. It looks like the whole
    power supply is by Osram. There is a block on the board which runs the lamp,
    designed specifically for that lamp. There is some detail in the wiring on the block
    but its not entirely obvious. The block runs on AC but I was going to plug it
    into AC, but the frequency is likely to be higher than 60 HZ.

  7. jango2

    jango2 Guest

    I posted a reply here and it vapourised. Then it wouldnt let me add a
    lengthy reply to another post, what is usenet up to?
    Find out from the customer if he saw a lamp timer warning before this
    happened. If so u need to find the lamp timer reset sequence of key
    presses at power up (from the op manual). Do NOT send the set back
    with the old lamp after resetting timer, it will implode liberating
    noxious gasses.
  8. GregS

    GregS Guest

    I was guessing the lamp "on" was OK since the lamp LED came on.

  9. jango2

    jango2 Guest

    Oops , sorry, my bad.Have you checked the thermal cut off on the lamp
  10. GregS

    GregS Guest

    No, but I looked for lamp voltage with an old meter.

  11. jango2

    jango2 Guest

    DC avlbl in ballast?
  12. GregS

    GregS Guest

    The Osram block is driven by AC. I have not measured anything yet on the power board.
    There looks to be an AC generator which feeds the output block.

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