[phat4l]

I've got an old Barco 800 projector that seems to be in pretty good working order except for the fact that the tubes are shot to hell. I have to turn the brightness up so far to compensate that retrace lines are highly evident even on relatively bright scenes and the black levels are anything but. The overall picture is also relatives fuzzy, is that something that could be fixed by new tubes?


Anyway what I am wondering is whether anyone knows where I might possibly be able to source new (or good condition pre-loved) tubes for such a beast. I live in Perth, Western Australia so this is a limiting consideration unfortunately.


If anyone has any ideas that would be great because otherwise I'm going to have to "downgrade" to an LCD pj as there is no way I can afford a new CRT and there is no where around here I am likely to be find a reasonably priced used one either.


Thanks.


Alex.

 

[Gatherer]

You have PM

 

[phat4l]

PM?


Sorry, I don't understand the reference?? Could you elaborate.


Alex.

 

[phat4l]

Ahh, just figured it out, private messaging right?


If so, unfortunately not. You can email me at [email protected] though.


Alex.

 

[phat4l]

No-one has any idea then??


So I guess I'll just have to junk the old girl ... any parts in there that might be of use to anyone?


Alex.

 

[Curt Palme]

Sounds to me like you have video output board problems, not tube problems.... Email me below for more info...


Curt

 

[phat4l]

I emailed you, did you get my message?


Really keen on finding out some info on this, it would be awesome if I could get this old pj performing well again.


Hope to hear something from you, my email is a couple of posts up if you didn't get my message and want to contact me.


Thanks for the offer of assistance, it is muchly appreciated.


Alex.

 

[kal]

Is your G2 set correctly? If yes, then I'm with Curt: your RGB output boards probably need some parts replaced.


Kal

 

[phat4l]

Sorry if I sound ignorant, but what is my G2 and how do I know whether it is set correctly?


Is there any way I can test definitively whether it is my RGB boards that are at fault?


Is there any way I can determine what condition the tubes are actually in?


If it helps with the diagnosis at all, another problem with the unit is a large degree of beam spreading, particularly on the blue tube, making it impossible to get a very sharp focus on anything. Is that a problem with the tubes or with another component?


Cheers.


Alex.

 

[Gatherer]

Beam spreading on blue is all to do with the G2 ala focus

I find it very Hard to believe you dont Know what the G2 settings are Perhaps you would be better off taking a look at the manual available here to down load
http://beamer.xs4all.nl/

Once you have read and have tried a few things for instance mechanical setup and G2 then you may find that people may be able to assist you further

I would follow the manual from scratch the Barco has a tutor in the menue system follow this and see how you go

Quote

If anyone has any ideas that would be great because otherwise I'm going to have to "downgrade" to an LCD pj as there is no way I can afford a new CRT and there is no where around here I am likely to be find a reasonably priced used one either..........................


This lead me to believe you use the projector for some time


Quote

Anyway what I am wondering is whether anyone knows where I might possibly be able to source new (or good condition pre-loved) tubes for such a beast. I live in Perth, Western Australia so this is a limiting consideration unfortunately.....................


Did you get my PM about some guy on australian newsgroups selling a 800 for $400 Aus tubes are great but says the Pj has a shut down problem even had the mount thrown in


anyway at the very least have a good go at the Pj setting up these are a very good home unit they put out a great image on DVD

 

[phat4l]

Thanks for the link to the service manual, I have been looking for something like that for a while without success.


OK I now know what you mean by the G2 controls (aka the electrical focus and gain controls right?). Well if that is correct then I have adjusted these previously, I just didn't realise they were known as G2 controls. These are the gains that are turned up high to compensate for the low brightness in the tubes, thus producing highly visible retrace lines and low contrast.


I am fairly familiar with all of the basic setup of the projecter (I have the owner's manual - which doesn't even list the "G2" controls) so all of my mechanical setup is right as best as I can get it and all of the standard setup accessible through the pj menu is also configured as best as I can achieve.


Am I correct in supposing that the G2 controls are the three electrical focus and three gain control pots? If so is there something that I should be doing to these that I am not aware of?


The service manual also describes a QUAD decoder+RGB Gain Control section G2, however, which includes some less accessible pots ostensibly for gain control, although it talks about setting them to a specific voltage using a 0.7v p2p reference source, which I do not have. Should I be trying to adjust these?


Thanks for all the help, it is really appreciated, and sorry if I seem a bit clueless, but I don't have any other way of finding this stuff out except through these boards.


Alex.

 

[kal]

Originally posted by phat4l
Am I correct in supposing that the G2 controls are the three electrical focus and three gain control pots? If so is there something that I should be doing to these that I am not aware of?


Yup - the G2's are the 3 gain controls. The 3 focus controls are simply called the 'electronic focus' I suppose.


The correct way to set G2 on your projector (and most other ES focused PJ's) is:


(1) Set contrast to 0/100 and brightness to 50/100.

(2) Display an all-black screen (0 IRE) from Avia or Video Essentials. Don't rely on a black screen during a 'normal' movie - they're not always 100% true 0-IRE.

(3) Adjust the G2's one tube at time until you can just see the rasters light up while looking INTO the tubes (not on the screen). Making all 3 tubes identical is more important then the exact level you set them to.

(4) re-adjust electronic focus for all 3 tubes...

The service manual also describes a QUAD decoder+RGB Gain Control section G2, however, which includes some less accessible pots ostensibly for gain control, although it talks about setting them to a specific voltage using a 0.7v p2p reference source, which I do not have. Should I be trying to adjust these?


No - as you probably guessed, these should have been factory adjusted. Is the gain of all 3 tubes roughtly the same now? (ie: When you turn the contrast all the way down and the brightness up, do all 3 tube rasters light up at around the same brightness value?) If someone had tampered with these then most likely the gain would be completely different on all 3 tubes.

Thanks for all the help, it is really appreciated, and sorry if I seem a bit clueless, but I don't have any other way of finding this stuff out except through these boards.


Actually, you seem quite knowledgeable! You understand the basic ideas so you shouldn't have any problems figuring all this stuff out from here on in.


Good luck!


Kal



Alex. [/b][/quote]

 

[phat4l]

OK, I tried the setup as you have outlined but I have a few more questions.


Is a pure black true colour image from an HTPC close enough to 100% true 0-IRE?


Even at the absolute minimum setting for the gains such that you can just see the raster when looking into the tubes, there are clearly visible retrace lines on all of the tubes, is this normal?


If I set the gains as specified at the point where the tubes just light up looking into them, then I don't see the retrace lines on the screen when I switch back to 100/100 contrast and 80/100 brightness with a normal desktop, but the the image is very dim and washed out.


Another anomaly is that if there is an area of bright colour somewhere on the screen then the areas to either side horizontally become even more washed out as if the bright colour is bleeding across the screen.


Also the blue tube is particularly hard to get focussed with the electronic focus compared to the other tubes, the best I can get is still farily soft and fuzzy.


Are any of these symtoms of worn tubes or dodgy FETs or is this likely just bad setup somewhere?


Anyway thanks for all the help, you guys are legends.


Alex.

 

[kal]

Originally posted by phat4l

Is a pure black true colour image from an HTPC close enough to 100% true 0-IRE?!


No! You really need to use the real thing. The HTPC black image is not beig passed through the video card's overlay. Use the real thing.

Even at the absolute minimum setting for the gains such that you can just see the raster when looking into the tubes, there are clearly visible retrace lines on all of the tubes, is this normal?


I'm not 100% sure what you're saying.... The raster *is* the regular scanning lines & retrace lines so if you see the raster, yes, you should be able to see all sorts of other lines.

If I set the gains as specified at the point where the tubes just light up looking into them, then I don't see the retrace lines on the screen when I switch back to 100/100 contrast and 80/100 brightness with a normal desktop, but the the image is very dim and washed out.


Since you're setting your Grid 2 gain (G2) while brightness is at 50, the end result where your brightness will be during playback will also be around 40-50 - not 80. Contrast varies and depends on a lot of factors including personal preference, but most people run barco's with contast between 50-75. 100 contrast is NOT required and is not normal.


Go through the steps again using a true 0 IRE image and see what happens.

Another anomaly is that if there is an area of bright colour somewhere on the screen then the areas to either side horizontally become even more washed out as if the bright colour is bleeding across the screen.


I'm not sure what this is.

Also the blue tube is particularly hard to get focussed with the electronic focus compared to the other tubes, the best I can get is still farily soft and fuzzy.


Blue's always harder to focus. Don't worry about it. Our eyes don't notice it.

Are any of these symtoms of worn tubes or dodgy FETs or is this likely just bad setup somewhere?


Not sure... if all 3 tubes are behaving the same, then I'd say no, since the bad transistors are usually on the neckboards (and there are 3 neckboards).


Kal

 

[ChrisH]

I think Curt hit it earlier....it's the RGB output modules.


If the G2's are turned all the way down and even a hint of visible raster, along with "scan lines" is evident.....then it seems that the 800's all-too-common problem of blown RGB output modules is the culprit. They are mounted on the chassis brace just above each tube....and are about 4 inches long, about the size of a fat candy bar.


By "scan lines" I'm guessing that Alex is describing a few pronounced, diagonal lines....not the hundreds of finer horizontal scan lines one would normally find under typical high gain or brightness settings. I've seen this condition many, many times in the 800's.


Alex, it looks like you have 2 choices: either replace the RGB output modules (not too hard too find used ones that work OK), or replace the failed components within each module. I seem to recall that Kal posted a thread identifying these components and how to replace the....transistors (I think). In the long run, replacing the failed components may be best since used modules might fail again at any time.


- Chris

 

[kal]

Chris is probably right... and I missed that part about retrace lines being visible even with the G2 turned way down. That's a tell-tale sign that it is indeed the RGB output transistors.


I still find it odd that all 3 RGB output boards would be behaving the same way... usually one will be much worse then the others....


If you can find the $2 2SK511 FET's I'd say go for it.... problem is sourcing these... they're a ***** to find.


See these threads:

http://www.avsforum.com/avs-vb/showt...ghlight=2SK511

http://www.avsforum.com/avs-vb/showt...ghlight=2SK511


Kal

 

[ChrisH]

Agree that it is rare for all 3 boards to go out, all at once anyway. But, it's possible they went individually, and maybe Alex either didn't notice or compensated with adjustments.....and now the image is finally intolerable now that all 3 are shot.


I recently picked up a BG801s and found all 3 of these RGB boards to be bad. Suprised a little, since I didn't think this happened much with the 801s model. Interestingly, adjusting the gain in one tube has a direct effect on the gain levels in the other two. Never noticed that before with an 800, but then I cannot recall working on an 800 with all three boards bad. Maybe the phenomenon is only when all 3 are bad.....or is only with the 801s' different electronic design.


- Chris

 

[Riktar]

Quote:

Originally posted by kal The correct way to set G2 on your projector (and most other ES focused PJ's) is: (1) Set contrast to 0/100 and brightness to 50/100. (2) Display an all-black screen (0 IRE) from Avia or Video Essentials. Don't rely on a black screen during a 'normal' movie - they're not always 100% true 0-IRE. [/b]

To ensure a 0 IRE couldn't a person generate a black picture (Photoshop, etc.) save it in a TGA format and then import it into a Video editor such as Media Studio Pro to create a NTSC legal movie? I have an old copy of Vegas Video and there is a setting that allows you to "clamp" any still image in the timeline to the NTSC (16 - 240) color range.


I was hoping I could create my own calibration movie in this way to facilitate easier calibration sessions.


Or am I missing something?



Regarding the 2SK511 FET's - How about someone does a "group" purchase? Or maybe one of the members that has a stash larger than what they can presently use would be willing to sell some? I know I could use 3.


Rick

 

[kal]

Riktar,


No you can't... simply put, it has to do with the output voltages of your video card. What guarantee do you have that your computer's brightness setting is set CORRECTLY to output 0 IRE at the correct voltage level?


When using something like TheaterTek, we're sure that the settings are correct because the video card's overlay (not desktop) brightness/contrast/saturation/etc have all been pre-adjusted specifically for ATI Radeon cards so if you play Avia in TheaterTek and use an ATI video card you KNOW that you're outputting (more or less) the exact same voltage range to your projector as a 'regular' set-top dvd player showing the same thing.


Kal

 

[Riktar]

I wasn't talking about playing the signal from the timeline, or using the computer for that matter. I should have elaborated on the prior post.


Let me complete the query by saying that after I have placed the image onto the timeline, created the file (VOB) and burned it to an NTSC DVD I would then pop it into the DVD dektop (Pioneer DV-C603) player that I use for movies. This is also the device that runs through my DVDO to the BG800.


I would not be using the computer to output the file directly. I would only use it to create a DVD to use in my Desktop player.


If I am still missing something, let me know.