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Vermin
Joined: 11 Sep 2009
Posts: 32
Location: Germany
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| Posted: Fri Sep 25, 2009 6:03 am Post subject: Try to fix an 8500 HDM |
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Hi there.
Befor 3 Weeks i have an HV Leak at the Anodecup after color Filtering the Glycol of my Marquee8500. The HV jumped into the Deflection Yoke Pins of the blue Tube. This HV Leak kills my HDM. H-Fail LED on the CLM. Changing the HDM with a older model of my Marquee 8000 fix the Problem and the Projektor is running.
I've followed some components measured like the HV sensitive Mosfets Q1, Q3, Q5, Q7, Q19. They are working properly.
I ordered a new 8500 HDM from someone in Oakfield. But i try to fix the HDM.
Anyone an idea what could be defect?.
Here you can look the Schematics:
http://www.2lss.de/2dcafe/gallery/displayimage.php?album=17&pos=0
Thankx ...Vermin
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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| Posted: Fri Sep 25, 2009 12:54 pm Post subject: |
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Look at any all of the resistors for any that are open, especially the fusible(safety) resistors on that board.
One other thing you can check since the Mosfets are ok(did you remove them to test?) is if the replacement HDM has the same Daughter board
then swap the daughter boards incase that is what got damaged, then you narrowed it down, swap the boards both ways also incase both the daughter and main board were both damaged. So put the bad boards daughter board onto the good HDM and see if it works, if not its the board, but then also take the good board and put it on the bah main HDM . This way you can see if both or just one board is shot.
Athanasios
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Fri Sep 25, 2009 5:24 pm Post subject: |
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if 34.9 KV really went directly into the yoke then your HDM is done,toast, Kaput.
However I've had leaks at the boot before and it usually arcs to the tube housing. the EMP pulse however kills the 2n7000 FET at location Q113 on the daughter board. Try swapping this and see what happens.
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Vermin
Joined: 11 Sep 2009
Posts: 32
Location: Germany
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| Posted: Sat Sep 26, 2009 8:49 am Post subject: |
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Thanks, Thanks, Thanks
The Projektor is running. I measured all the 2N7000 on the Daugtherboard. One of them is not turned on when loading the Gate.
This is realy the best Forum für CRT Projector in the World wide Web.
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Sat Sep 26, 2009 3:24 pm Post subject: |
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Great, now that it's running it's time to upgrade. Part of being a CRT guy is never leaving well enough alone 
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