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uhx
Joined: 22 Aug 2009
Posts: 10
Location: Germany
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| Posted: Sun Nov 22, 2009 11:10 pm Post subject: Barco 801s HV problems |
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Hi All,
unfortunately only a few power-on hours after getting my Barco 801s back to life (green tube was shortened) there seems to be again a problem with the high voltage. The picture suddenly began to dizzle, got blurred and finally collapsed. At the same time we could hear a sizzling from inside the projector. After a few minutes we again turned the projector on, and had a normal picture, but only for about 30 seconds - then same game as before...
As there was obviously something wrong I opened the projector to see, if some LED was lit. While I'm not sure about this, I thing a saw a blue/violet glow inside the blue tube when turning on the projector - just like in one of these plasma lamps or a fine beam tube. Again there was a sizzling and only a few seconds after powering on HV dissapeared with a pop and the Hold down LED on the EHT board was lit.
In a third step I pulled out the blue tube from the HV splitter and the focus board (when the green tube was shortened, this brought back a picture), but still the hold down LED is lit after a few seconds. Even when pulling out all three tubes and the HV input on the focus board, the hold down LED goes on.
Does anyone have an idea about was could be wrong or suggestions for what I could check additionally?
Thanks,
Ulli
P.S.: I don't know if this is important, but I mention it anyway: After changing the green tube, I noticed that all three green LEDs on the video output board (the ones labeled "LED must be off") where lit, but ignored it, because I had a good picture.
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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: Mon Nov 23, 2009 2:56 am Post subject: |
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IT sounds like your blue tube is shorted. When pulling the HV lead from the blue tube, you also need to pull the focus lead off the focus block going to the blue tube. THe focus lead will load down the HV, and it will go into shutdown.
Pull the HV lead and the focus lead and see if the red and green tubes work.
Note that a tube shorting in an 801 is very rare indeed, let alone two within a few hours. Is the image shooting off the side of the tube face? THat can cause tube implosion.
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uhx
Joined: 22 Aug 2009
Posts: 10
Location: Germany
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| Posted: Mon Nov 23, 2009 9:24 am Post subject: |
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Current status is, that I pulled off all three tubes, the main HV supply as well as the focus cable. But holddown is nevertheless lit.
I had an oversized picture before the green tube was shortened. Could it be that this also damaged the blue one and it shortened a few poweron hours later?
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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: Mon Nov 23, 2009 3:15 pm Post subject: |
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Either the EHT board or the quadrupler or even the HV splitter is defective. An oversized pix means the HV is too low. It's hard to say how exactly it blew, but you do have HV problems now.
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uhx
Joined: 22 Aug 2009
Posts: 10
Location: Germany
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| Posted: Mon Nov 23, 2009 4:59 pm Post subject: |
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| Curt Palme wrote: | | An oversized pix means the HV is too low. |
Oh, by oversized I meant, that the projector ran with a picture, that was shooting off the side of the tube face, for a few hours. This was due to wrong adjustment and not due to an error of the projector. After replacing the green tube I readjusted everything, without overshooting.
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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: Mon Nov 23, 2009 5:10 pm Post subject: |
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Oh I see. That was probably enough to weaken the blue tube, and it ended up failing. 
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