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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Wed Jul 22, 2009 9:19 pm Post subject: Strange noise with BG808 |
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Hello,
I noticed a strange noise on some pictures (mainly with large bright backgrounds) when watching movies on my BG808. It comes and goes from one scene to another (depending on the bright background, I think).
A few weeks ago, I calibrated my pj and set the contrast level to 58. Since then, the noise is there. The noise seems to be louder when I increase the contrast level. Around 47, the noise almost disappears. I also noticed that when I hear the noise, the bright background looks very instable with horizontal lines flashing (top of the picture). I tried to locate where the noise came from and it seems to be near the EHT, G2 and SPMS. Any idea what is wrong?
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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: Wed Jul 22, 2009 10:33 pm Post subject: |
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You've nailed the problem, you have some HV arcing somewhere. Most likely it's right in the quadrupler, but it can also be a tiny leak in the main HV or focus cable, HV splitter or one of hte HV leads.
If you let it run, I'll bet in the next month or so, the set will go into HV shutdown mode, and the EHT red light will come on. If so, then the quad is bad. I've seen this a few times before. I'd run it until it dies completely, I've got spare quads.
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Wed Jul 22, 2009 10:46 pm Post subject: |
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My BG500 did that same thing and I think it was that big white transformer in smps. I couldn't hear it with hushbox so never research it more.
Try to hear where it comes with rubber hose.
Maybe transformer/coil varnish have gone bad.
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jkruger
Joined: 24 Oct 2007
Posts: 2435
Location: Carlsbad, CA
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| Posted: Thu Jul 23, 2009 2:49 am Post subject: |
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| Ile wrote: | | Try to hear where it comes with rubber hose. |
Would it be wise to make sure it is a non-conductive rubber hose? 
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Thu Jul 23, 2009 5:01 am Post subject: |
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My BG808 makes a buzz from the SMPS - a transformer I think. It's not the EHT or Quad (I'm learning Barcospeak).
It varies with the picture.
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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Thu Jul 23, 2009 7:52 am Post subject: |
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Mark,
It looks like we have the same problem. Have you noticed that increasing the contrast, increase also the noise?
Curt, Ile
If I manage to find that the sound comes from the SMPS, what should I do? I don't have a hushbox like Ile, so the noise is pretty annoying 
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Thu Jul 23, 2009 8:57 am Post subject: |
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| Corleone88 wrote: | | If I manage to find that the sound comes from the SMPS, what should I do? I don't have a hushbox like Ile, so the noise is pretty annoying |
If it is smps transformer. Check if that white plastic cover can be removed, then you can add new transformer varnish to windings. Other option is to find newer and less used smps, 808s would be best donor, it have bit newer desing R7621705 -> R7621706.
Coils can be hot clued to reduce buzz.
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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Thu Jul 23, 2009 8:52 pm Post subject: |
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Well, I tried to locate the noise and it seems louder near the black metal part with "X radiation warning" written on it.
What is it and can it explain the noise?
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Thu Jul 23, 2009 9:03 pm Post subject: |
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If you can hear the noise then your sound system isn't turned up loud enough. 
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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Fri Jul 24, 2009 3:33 pm Post subject: |
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Thanks for your advice, I'll think about it
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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Sat Jul 25, 2009 6:54 am Post subject: |
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I tried a few things last night : I unplugged one tube and left the other two plugged. I did it for R, G and B. Each time the noise disappeared. But the horizontal black lines flashing on the top of the picture were still there.
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Tom.W
Joined: 09 Mar 2006
Posts: 6635
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| Posted: Sat Jul 25, 2009 7:02 am Post subject: |
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| Corleone88 wrote: | Well, I tried to locate the noise and it seems louder near the black metal part with "X radiation warning" written on it.
What is it and can it explain the noise? |
Like Curt said sounds like a bad quad. That part you are referring to is the EHT module. The high voltage quadrupler is directly underneath it.
Do a little homework !
http://www.curtpalme.com/Barco808_Layout1.shtm
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Sat Jul 25, 2009 8:59 am Post subject: |
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How would contrast and picture information affect to problem if it's HV related?
Could that black flashing line in top be blanking? Adjust top blanking one klick to top...
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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Sat Jul 25, 2009 10:14 am Post subject: |
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No I cannot blank them unless I lost 15cm of the picture on top. It is not just one black line. It looks like multiple blacks lines (looks not stable).
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Jul 25, 2009 2:33 pm Post subject: |
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Is there any way you can snap a pic of those lines?
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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: Sat Jul 25, 2009 2:55 pm Post subject: |
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When you increase brightness and contrast, you put more of a load on the HV section, also if there's a bright scene compared to a dark one. The load causes the quadrupler to arc more internally (assuming that is what the fault is), and you see lines, or shaking or noise in the picture. I'll bet eventually the EHT will shut down.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Sat Jul 25, 2009 3:00 pm Post subject: |
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| Curt Palme wrote: | | When you increase brightness and contrast, you put more of a load on the HV section, also if there's a bright scene compared to a dark one. The load causes the quadrupler to arc more internally (assuming that is what the fault is), and you see lines, or shaking or noise in the picture. I'll bet eventually the EHT will shut down. |
Exactly why I wanted to see what type on lines.... 
They are called fireing lines....
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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Thu Aug 06, 2009 10:07 am Post subject: |
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Hi,
I am back because I got a BD801s with some spare parts for my BG808.
I have these following boards in my BD801s: quad R761743, splitter R7617447 and EHT R7617427. If I assume that my 808 quad is faulty, can I swap my R7622091 with a R761743? My 808 has also the splitter R7617447 and EHT R7617427.
When you change the quad, except shutting down the pj, what else do I need to do?
Thanks.
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Decibel
Joined: 31 May 2007
Posts: 904
Location: Roma - Italia
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| Posted: Thu Aug 06, 2009 11:20 am Post subject: |
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| Corleone88 wrote: | | can I swap my R7622091 with a R761743? |
Yes but these quads have different mounting holes.
You must make an adapter.
Tested and working in a BG808, I swap both quads with success.
| Corleone88 wrote: |
My 808 has also the splitter R7617447 and EHT R7617427. |
Correct.
_________________
Domenico (Barco fan!)
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Corleone88
Joined: 09 Dec 2006
Posts: 474
Location: France
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| Posted: Wed Aug 12, 2009 7:50 am Post subject: |
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Ok, so to be sure not to kill myself , I can put these set of boards on my BG808 without any problem :
quad R761743, splitter R7617447 and EHT R7617427 ?
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