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mikelue
Joined: 19 Jul 2012
Posts: 3
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| Posted: Tue Sep 18, 2012 5:28 am Post subject: BARCO DATA800 HV problem (shortetd tube ?) |
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Sorry for my bad English. I'm German and have a Barco DATA 800 with clean tubes on my ceiling since 2005.
Last month my Barco failed with a dead EHT board (R761742). The fuse (F1) was blown and Transistor (Q7) was dead. After replacing transistor and fuse, the Barco fails (F1&Q7) 10 minutes after power on (during this time the picture was ok).
Then, i've replaced the EHT board and the quadrupler (same part numbers from a working spare DATA 800 with bad tubes). First it seems to be ok (except that the brightness/contrast adjust scales don't show), but then it fails again with F1 and Q7 dead after 15 minutes.
Next try was replacing the splitter (R7617447). Now the picture slightly jumps/pulses (brightness and size) and after 3 minutes i've noticed a very hot transistor (Q7). Before the EHT fails again i've switch the projector off.
My last unsuccessful try was replacing the focus board (R761745).
Now i'm totally frustrated.
Can one of the tubes have a failure though they seem ok?
How would I best troubleshoot the problem?
thanks for your help
Mike
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mikelue
Joined: 19 Jul 2012
Posts: 3
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| Posted: Tue Sep 18, 2012 8:36 am Post subject: "check powersuply for dryed solder joints" |
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@arbey
Thank you for the private message. (i can't send a answer because i have less then 5 posts)
I've resoldered most of solder joints (all the critical) in the SMPS. Many of the big capacitors are replaced with new ones (17V problem in the past).
If the SMPS can be the source of the HV problem, i can try the SMPS from my spare Barco.
Regards Mike
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Tue Sep 18, 2012 1:50 pm Post subject: |
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The SMPS won't be the issue. I had a 708 do this once, and it turned out to be a bad focus block that apparently was loading down the quadrupler. I'd change the focus block.
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mikelue
Joined: 19 Jul 2012
Posts: 3
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| Posted: Tue Sep 18, 2012 3:24 pm Post subject: |
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Many thanks for your answer Curt !
Do you mean the focus block mounted on the focus board ?
The complete focus board i have already exchanged. This was my last idea and hope (can overload the Quad).
What's the best way to measure (detect) an EHT overload ? (current flow in the +300V rail ?) I will not kill more EHT-Transistors.
Regards Mike
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