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Revox
Joined: 13 Feb 2008
Posts: 158
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| Posted: Thu Oct 29, 2009 12:49 am Post subject: 8500 sporadic "puff" - HDM falure |
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Hi, at the last film session the following happens:
I heard a quite "puff" out of the Marquee and the HDM Falure LED flashed for a short time. Picture was set of for a short time.
This falure happens one time per our.
I resoldired the HDM already (had some problems with the contacts of the daughter board). But this was not the problem.
I wonder where the puff comes from, no smell, nothing! Mabe a HV leak?
Are these Problems "well" known?
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Thu Oct 29, 2009 1:38 am Post subject: |
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never heard a puff before? Can you be more specific? Is it like a snap, like maybe high voltage discharge/leak?
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Nashou66
Joined: 12 Jan 2007
Posts: 16171
Location: West Seneca NY
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Revox
Joined: 13 Feb 2008
Posts: 158
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| Posted: Thu Oct 29, 2009 7:54 am Post subject: |
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Ok, i know how a 37kV sounds like, and a teslacoil. Both sounds are very agressive!
My sound is with less high frequency parts. Let me say blunt! Like a Cab is exploding. But there is no smell!
What do you men with check? The problem is that the falure occurs not very often, so i think when i check the transistors around C533 they will be ok?
Yesterday night i isolated the HDF-Coil pin's and the Anode Cup again (but not very good, because i would't disassemble the whole PJ.
Do you know the sound of the protection circuit? Maybe, what i hear is the protection circuit and not the Bug?
A view day's ago i had problems with the
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draganm
Joined: 08 Mar 2006
Posts: 8990
Location: Colorado
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| Posted: Thu Oct 29, 2009 5:51 pm Post subject: |
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this is a tough one to really diagnose. the MArquee protection circuits simply shut down the high voltage, I have never heard of it making noise.
Check the 3 belly fans, make sure they are all working. If one is dead, then maybe the HDM is shutting off thermally and what your hearing is a relay? 
The HDM switches from running the coils in parallel to in series depending the sweep frequency. try running the machine at 480P low frequncy and see if the problem goes away?
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Revox
Joined: 13 Feb 2008
Posts: 158
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| Posted: Thu Oct 29, 2009 8:10 pm Post subject: |
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The pj runs 6hours today and nothing happend. Maybe the isolation action was the right decision!
But i think the failure will happen again in the next movie.
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