Just thought I would add a note, I bailed out , I bought a BG1209. Before the EHT gave me trouble, and I sent it to Curt for a repair, I watched a few segments in my DVDs that gave me lots of streaking. The results? .......... NO STREAKING!!!! non at all, it was great., and thats with a very rough setup (no g2 or astig yet) . So I wouldn't say this was a cure but it worked for me. :)


Regards

So the solution is to buy a Barco 1209? Brilliant! Why didn't I think of that? ;)

-Mike

A Barco 1209 solves everything.
I have no streaking issues with my Barco Vision 1609 and Data 800.

It's well known that whole 12** series (16** is same) is streakfree, same with 500/800 and Cine series...

I'm having the same problem with my BD808S from 1997 (8500h).

After reading thus thread i removed the ABL jumpers and when the machine is warmed up the streaks are gone.

Only problem is my barco was isf calibrated, when i remove the jumpers the calibration is gone.Removing jumpers change G2 level, that might having effect to not see problem.

If it's not there after recalibration I'm very suprised.

This exact point was raised before (some time back) and to my knowledge has never been fully answered. May well be that modding the ABL simply masks the problem but I wonder if somewhere in amongst all the boards inside a Barco there isn't a small cap or something that no-one has ever found thats causing all the heartache
PaulI'm pretty sure it's not el-cap, because I have changed every one. :)

I don't believe removing ABL can anyhow mask that problem, it's more likely that this kind ABL system generates streaking with certain circumstances.

Have anybody else found out that removing abl jumper elevate G2 quite much?

I'm just guessing here, but that have happened to both of my streaking 801s. Maybe G2 have been too high when rgb amps+ABL have been calibrated in factory. If that is correct, then ABL system have to elevate cutoff voltage very much to blank the beam. Maybe ABL doesn't work correctly if it have to compensate cutoff voltage very much all the time. Maybe I check that some day.

Removing jumpers change G2 level, that might having effect to not see problem.

If it's not there after recalibration I'm very suprised.


I can't calibrate it myself, don't have the equipment. So it is quite expensive to let someone else come and do it. And then see that the problem maybe still there.

Removing the complete ABL circuit is to tricky for me at the moment.
Because it's not easy do undo the changes when i doesn't solve the problem

I've also changed most every el-cap with no effect on streaking...I did not do the SMPS (mine had good quality caps in it) nor did I do the EHT board.

I agree with Ile's general comment...the best chance of eliminating or minimizing streaking may be to go through the Barco manual and make sure that your isf'r checks every adjustable voltage and setting for every board. This should include the mechanical setup on the geometry. A good mechanical setup can go a long way towards enhancing picture quality. My streaking is minimal but still there.

Ile-have you ever checked/adjusted the Chroma Rejection circuit on the Quad Decoder to see if that has any effect on streaking? I was about to check just that very thing but my oscilloscope quite working.........

Don't know if its related but........

Ile-have you ever checked/adjusted the Chroma Rejection circuit on the Quad Decoder to see if that has any effect on streaking? I was about to check just that very thing but my oscilloscope quite working.........

Don't know if its related but........Haven't bothered, because RGB inputs doesn't go through Chroma Rejection circuit. Decoder is used only for unpacking RGB information from composite and s-video inputs. When used with rgb, it only makes few voltages, generates clamping pulse, sharpness-, contrast- and brightness voltages...

RGB goes from driver board connector straight through to main board connector and after that to RGB amps by coax. I have passed those needless connections, now RGB signal goes straight from driver to RGB amps by coax...

I've also changed most every el-cap with no effect on streaking...I did not do the SMPS (mine had good quality caps in it) nor did I do the EHT board.


You're wasting time pulling and replacing caps for this problem. And you'd be wasting money by using expensive caps in these same circuits. Over the past four years I've tried almost every designer name cap out there, and the best that i could tell between the super caps and the regular 10cent caps, is that the designer caps looked better in the circuit. And depending who I was discussing things with, it just sounded so much better to say "I took out the cheap caps and put Blue gates" (or whatever). Other than being a good conversation piece, it's a waste of time and money. I think the designer caps work best in audio only.

I still have Pete's Barco 808 in my shop. Last week I took on a project for one of my commercial customers that involves the 808 and later 908. Though the problem that i'll be working on has nothing to do with streaking, I'm going to look at that as I go along. And because the circuits are so straight forward, I'll be helping you guys get to the bottom of this streaking problem. So far, I've been studying the diagrams. Now, I have two goals here, One is to solve a problem for my customer (priority), and the other is to finish what I had started with this 808. And in doing so, I'll be able to put my hands on that streaking problem.

If I'm able to solve the streaking problem, I'll share what I found openly. Again, my only interest here is solving a particular problem for my commercial customer, and finishing up Pete's 808.

Thanks Mike........

I thought new caps would make the signal cleaner...but it didn't really change that much. I don't think I ever really expected new caps to stop streaking.

Streaking is related to something more complicated than just a capacitor...something I don't understand. BUT, I'm very interested in what you may find out. It's one of the last bugs I have left to tackle on the 808. The other is related to video noise and is probably coming from my scaler.

Streaking is related to something more complicated than just a capacitor...something I don't understand

Well, let's look at that closer. Streaking is usually more likely to come from the neck boards, and would be associated with bandwidth failure. Or failure to handle the bandwidth of the signal being used. It is complicated indeed, but once you know what can cause it, it's a lot easier to isolate.

On the neck boards it's usually caused from the Vcc supply cap, (or a breakdown of the output device itself). But that would be more likely the cause on single out putput (high voltage) drive boards, rather than the higher performance differential (dual amps that drive both Cathode and G1 grids separately). You'll not likely find a leaky cap causing streaking on the lower volt vcc rails of differential drives.

The second (and more complicated) place that could be a source for it, is the semiconductors (IC's, transistors, diodes) in the video chain before the final output stage on the neck boards. Some semiconductor devices manufactured during the 90's would break down (ie. the Comlinear CLC409 used in the marquee 8000/9000). These devices worked fine initially, but later loss some abilty to handle the rated bandwidth.

Third, is your pulse rails (DC restore, blanking, etc). The rails would need to be as clean as when the projector was first manufactured or whatever noise is on those rails, could cause streaking in the signal chain. Because those pauses are directly feed (somehow) into the signal chain itself.

Fourth, the pulses would need to be measured to make sure they are accurate. Some designs use multiple pulses along the video chain for clamping and other reasons. It's very important that these pulses are mathematically in the right multiples with each other to keep that signal chain noise free. Likewise, the circuits that produce, time and distribute those pulses would have to be checked for proper freqeuncy (pulse width). This is probably where the caps would more likely need changing, but if that's the case they are usually low value electrolytics or tants, and the exact value is a must for replacement. A larger value can further effect the timing of that circuit, so stay with what's on the cap.

That's enough for now, and that should get you going until I can get back with you on this and join in later..

I might not have a Barco, but I might just file that post away for future reference. :)

Thanks Mike

Mike,

It could be good idea to start digging from ABL pulses, because c-pulse are known to be distorted lest in those three streaky units we have scoped. Removing whole abl system seem to eliminate streaking, so that also referral to abl problems.

I have also other abl related hunch that I'm going to check next time I took hushbox down.

Good luck!

I have also other abl related hunch that I'm going to check next time I took hushbox down.I took my hushbox down, because I tested my friend 808s SMPS that I fixed...

I did some tests with ABL amps, but no help. :confused:

So I put non ABL amps back. :D

I experience the same problem with my BG 801s. It is only visable in some scenes and occurs inconsistently. When it does show up it is only minimal, not as bad as the examples I have seen here.
The Barco has ~7000 hours on the chassis and the blue and green tube have been changed for brand new ones about 300 hours ago. 2 years ago the Barco has been ISF calibrated. When I look directly into the tubes streaking can be seen on the red and green tube only.

As long as this is not an omen of an amp going bad, I am not going to do anything about it.

Also one other Finnish 801s owner got tired to streaking and I loaned one modded amp to him, so he could test is that helping. Amp removed streaking from tube he was testing, so he ended to remove abl from his own amps according to my procedure.

http://www.z -photography.com/Barco/Removing_ABL.pdf
remove space after z...

Hi Ile,
I wonder if your modded amp could solve my problem. I got a BD808 and I've got similar streaking in all 3 tubes and it's getting worse. Once you noticed it you see it all the time.
I thougt that it would be in the videochain before splitting to the 3 tubes simply because it's so similar but if you experience is another it would be worth a try.
Have you had the same streaking in all 3 tubes or what ? Do you think it's worth the risk to make the mod ?
Regards
Mads, Denmark

Hi Ile,
I wonder if your modded amp could solve my problem. I got a BD808 and I've got similar streaking in all 3 tubes and it's getting worse. Once you noticed it you see it all the time.
I thougt that it would be in the videochain before splitting to the 3 tubes simply because it's so similar but if you experience is another it would be worth a try.
Have you had the same streaking in all 3 tubes or what ? Do you think it's worth the risk to make the mod ?
Regards
Mads, DenmarkIt's same problem in BD808, I have seen it in all 808 that use same 75 Mhz rgb amps.

MP's just released mod for 808 (http://www.mpmods.com/Barco1.shtm) include this streaking fix.

I made mod to newer version of 75 MHZ amp (7621736) used in BD808s. Component layout is same, so same instruction can be used.

Finnish BD808s owner reported that streaking was gone, picture was more stable and cleaner. He also mentioned that shadow details was better after mod.

I made mod to newer version of 75 MHZ amp (7621736) used in BD808s. Component layout is same, so same instruction can be used.

Finnish BD808s owner reported that streaking was gone, picture was more stable and cleaner. He also mentioned that shadow details was better after mod.

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).

That said, the streaking I did observe was identical in ALL 3 tubes. Because of this, unless the streaking was on new projectors from the factory, I find it hard to believe that ALL THREE 75Mhz Amps degraded identically.

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.

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. :D 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...

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.

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

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. :confused:

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. :confused: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.

Bruce! You're still kicking!!

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.

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