Barco Streaking Survey - Page 10 - AVS Forum
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post #271 of 276 Old 07-04-2007, 10:30 AM
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Quote:
Originally Posted by techman707 View Post

I find that very interesting. This thread has gone on for a long time with people posting all different observations referring to their BG808's streaking problems, many with different results. The few BG808's that I have had or sold either didn't have any visible streaking, or it wasn't objectionable when properly adjusted (meaning I could only see slight streaking with the brightness turned up too high).

I found that interesting, because I have seen it in every Barco that use 7621735 or 7621736 75MHz amps with properly adjusted brightness. Streaking is pretty faint and can be seen only in total darkness, but it have bothered me in every one...

That crappy designed ABL can also cause kind of small flickering in high contrast scenes. That is something I have seen also in BG808s with 120 MHz amps...

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Originally Posted by techman707 View Post

Just in general video terms, "streaking" is tested using a high contrast test pattern that has a black background with a white box. Just from experience, it can usually be traced to the HVPS, which could be just a poor design. The problem is that it can't respond to the transition with enough power or fast enough at the rise point, which on a scope shows a slightly rounded peak instead of a sharp corner. However, bear in mind that in reality, nothing is perfect.

That is same streaking I'm talking about and I doubt that it have nothing to do with SMPS, because BG808s use same SMPS that BD808s but without streaking.
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post #272 of 276 Old 07-04-2007, 10:40 AM
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Quote:
Originally Posted by Ile View Post

I found that interesting, because I have seen it in every Barco that use 7621735 or 7621736 75MHz amps with properly adjusted brightness.

That is same streaking I'm talking about and I doubt that it have nothing to do with SMPS, because BG808s use same SMPS that BD808s but without streaking.

I hear what you're saying, but there have been so many different streaking descriptions from people, from none at all to unwatchable. I just find it strange that if all three tubes have identical streaking that all three RGB amps could be equally degraded.

However, since you say that the streaking has been on EVERY BG808 you have ever seen (and I assume you have seen brand new ones), maybe the AMPS were just wrong for the design to begin with. Yet, I find it equally hard to believe that Barco was sending out newly manufactured projectors that had streaking out of the box. But then again, I've never had or seen an out of the box BG808.

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post #273 of 276 Old 07-04-2007, 10:52 AM
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Quote:
Originally Posted by techman707 View Post

However, since you say that the streaking has been on EVERY BG808 you have ever seen (and I assume you have seen brand new ones), maybe the AMPS were just wrong for the design to begin with. Yet, I find it equally hard to believe that Barco was sending out newly manufactured projectors that had streaking out of the box. But then again, I've never had or seen an out of the box BG808.

I haven't seen brand new 808, but I still believe that problem have been there out of the box. Actually I remember that Barco was actually admitted it to one of their rep. I believe it was not big issue for commercial customers, because most of those units was sold to presentation use where it can't be seen.
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post #274 of 276 Old 07-04-2007, 03:40 PM
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post #275 of 276 Old 08-21-2007, 09:12 AM - Thread Starter
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Hi Guys I havn't been on for a while , good to see this thread is still kicking. My 1209 has got to go, anyone want to take it down ? Just PM me .

Regards John.
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post #276 of 276 Old 08-24-2007, 05:31 PM
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I have a mod that corrects the streaking in the 808 if its the leaking cap issue.

Some of the most common problems come from the VPH06 chip.

They can fail 1/2 way causing focus issues and also streaking.

IT depends on the build number. Some of the early ones had much more problems. There is a small number at the bottom to tell you the production number that is when it was produced at the factory. This does not always line up to the year of the unit because sometimes they were shipped or stored at different years.

Greg

Gregory C. Eisemann Senior Electrical Engineer, Satcom Engineer, Opnet Engineer, Network Engineering, Satellite Engineering
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