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Barco 808s powers up, and then dies.

Discussion in 'Projectors, Screens & Video Processors' started by bpasco, Aug 9, 2004.

  1. bpasco

    bpasco
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    My greatly beloved Barco 808s had a new, ah, feature. After about 15 minutes of use, the screen goes black. If turned off, the picture will come back for a couple of minutes, but then goes black again. Perhaps it is overheating? Hopefully this is something a reasonably resourceful person can fix, since I don't really relish the idea of demounting it from the celing and hauling it out of the basement to the repair shop. Any ideas are greatly appreciated.
     
  2. secstate

    secstate
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    Are you comfortable opening the projector while on the ceiling? There are a couple of troublshooting LEDs that may help locate the problem. If you are comfortable post here and I will tell you what to look for. Also I know of a decent Barco tech in Silver Spring (I saw your location as DC) and I can give you his name/number and email address if you PM me. I recently moved to Central VA from DC in the last year.
     
  3. bpasco

    bpasco
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    With apologies for the delay - I took a week of vacation - I'd very much like any insight you can give into what I should look for to diagnose this problem. I installed and set this thing up, and while self educated in this make up in entheusiasm what I lack in actual technical know-how. So I'm more than comfortable opening the box up to do a little diagnosis. If you can coax me through it, I'm a willing pupil. Should the problem require a little more than I can provide, I also welcome your passing on the name of the tech you recommend. Again, many thanks for the help.
     
  4. Roland @ B4

    Roland @ B4
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    Brant
    I suspect a component of your EHT circuit is failing. It could also be the power supply.

    When the picture fails do the fans continue to run?

    when the PJ fails, you open up the projector cover and the rear metal lid. you will see a row of Green LEDs are they all on?
    Also while you are there above the fan on the same side of the LEDs is a black card with white writing there are two holes in the card can you see a red LED?
     
  5. bpasco

    bpasco
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    Roland:

    Thanks for weighing in.

    When the CRTs go dark, the fans continue to run and the chassis seems to be powered up.

    The power supply, the R7625061SM Power Supply2+G2 board, has all the green LEDs on. There is also a red LED in the row which is off. I presume this is as it should be.

    I note, however, that the other component you discuss, which my documentation pegs as the R7617427EHT Generator, has no LEDs on I can see until the picture goes dark. At that time, I can see a single red LED on through the holes you mentioned.

    Someone else suggested elsewhere that it could have something to do with Coincidence on the Controller board. Thoughts on that?

    Again, thanks very much for your help.
     
  6. Roland @ B4

    Roland @ B4
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    £1 says your Quadrupler has failed. these are not repairable but you may be able to get a used one.
     
  7. bpasco

    bpasco
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    Roland:

    Thanks for your insight. While I have your attention, permit me to further demonstrate my helplessness by asking for some clarification. My parts list does not specifically list a "quadrupler." The only part on the parts sheet with "quad" in it is "R762745 Quad Decoder+Comb filter." Is that what you mean? If that is not it, can you help me identify the component at issue?

    Additionally, I presume that a red LED on one of the boards is a fault indicator. (Pls. correct me if I'm wrong here.) What is the relationship between a fault showing up in the EHT Generator and a failure of the quadurpler?

    I appreciate your willingness to advise we the less technically astute of the world.
     
  8. JMPremier

    JMPremier
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    the quadrupler is the "eht transformer" that supplies the 37kv, it has the thick red wire coming out of it
     
  9. bpasco

    bpasco
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    Thanks, I'll crack the case and look... but I'm at a loss as to the formal name of the part which I may need to order. The Barco document I have which lists the various components of the 808s lists three compnents with the term "EHT": R7617427EHT Generator; R762718 EHT Splitter; and R7617447EHT Splitter. None of these seem to be particularly relevant. A text search on "quadrupler" is equally uneventful, nor does a search for "transformer" turn up anything. I may need a more detailed document, but this one purports to identify all the boards in the box. Perhaps this should as much as anything serve as a request to the host of this site to permit uploading of referance documents so that a common term of referance can be established? I'm grateful to you for your willingness to help, and apologize for my own inteptitude here, but would greatly appreciate your assistance in identifying in a way which would facilitate my placing an order the precise component it is suspected that I need to replace.
     
  10. JMPremier

    JMPremier
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    there are 2 main components that have the thick red eht leads connected
    the quadrupler is the one that has two red leads one thicker than the other
    the splitter has four red leads one from the quadrupler going in and 3 coming out one to each tube
    you will also see a small sticker on each component with the barco part number 76xxxx
    as for which part has failed roland is the all seeing all knowing guru ;)
     
  11. bpasco

    bpasco
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    For the record, I put the question to a tech at Barco and got the below response. I hope it is helpful to anyone in a similar situation.

    -------------------

    If you are getting a red LED on the EHT Generator, this indicates an "EHT Hold down". This indicates an EHT failure of some kind. It could be the Quadrupler, the EHT board, the Splitter(unlikely), or a failing crt. Visibly inspect the Quad for any bulges or pregnant spots. This would indicate a bad quad. To check the CRTs, disconnect the CRTs high voltage lead to/from the Splitter, and disconnect its Endstage or RGB Output Amplifier also. Do this for 1 crt at a time, and if the HV or EHT stays up without that crt, then that crt is bad. Be careful that the unit is never powered up without the quad plugged into the Splitter input. Before and After the unit has shut down into EHT hold down, measure the feedback on the Splitter. There is a small coaxial cable that is soldered to the Splitters small sub board. There is a Divide by 1000 circuit on this, and so instead of reading 34,700V DC, we should read about 33 - 35V DC. This is measured at the solder point of this coaxial cables center conductor. If it reads below 33V at startup, the quad is probably at fault. If the quad is not pregnant, it is probably good, but this is not for sure, just likely. If the quad looks okay, and the crts prove not to be the cause, then I would look at the EHT Generator.

    Hope this helps. Good luck,
     

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