CurtPalme.com Home Theater Forum

[matze584]

Hi together!

Firstly thank you all for this great forum Hopefully we are able to get my
old Lady fixed!

Since one and a half year now, i own a Barco-Graphics 400 CRT. And lets say, all of the time
it behaves very strange.
Lets define it this way:

The BG400 is connected to a PC serving as a media-PC in my livingroom. Here i installed
PowerStrip to easily adjust the Video timings generated by my VGA-Card.
For the composite-negative-sync problem i built a sync pulse rectifier by
means of autodetecting the sync polarity sent by my PC and invert and mix them
accordingly to suit my Barco's needs.
Shown by some testruns using a frequency-generator and an oscilloscope, this circuit works as intended.

So i tried to setup my CRT-Set basing on the instructions in the installation manuals.
But unfortunately with no luck at all.
The picture seems like it starts on the end of the scanlines on the left side of the tubes.
Hm.. lets say: it starts even more on the left... about one third of the picture gets lost.
Another effect is, that black (or darker) horizontal bars are spreaded all over the picture.
The horizontal phase-control on the remote-control-box is maxed out. No way to get the picture centered
on the tubes.

OK, reading all along the informations about old Barco CRT-Sets in different Web-Sites and Forums,
i tried to get it working by means of resoldering all soldering-joints on _all_ PCBs.
There was real one cold solder joint beneath the other :-/
Also in one run, i changed all of the electrolytic capacitors on the SMPS-Board and in the convergence-panel.
On the convergence-Panel i also changed every potentiometer.
Finally i also readjusted the SMPS according to the service-manual.

Especially the new capacitors and potentiometers had a great effect on convergence-stability and ability
But,.. however.. the strange sync-problem was not affected.
Some playing with Powerstrip showed up, that if i increase the back-porch value very much, its possible to center the picture on the scanlines (and thus on the tubes). But also, it decreases the effective picture-width much.
Nothing to wonder about :-/ At least, a back-porch of 512px is needed at a resolution of 1024x768 to get the picture centered. This is about one third of the whole scanning-interval!

Even the internally generated testpattern is locked to the left end of the scanlines. With increasing horizontal
frequency it moves more and more into the ends of the scanlines until it wraps around to the right side in the 64kHz setting. This is exactly the same effect i can reproduce with my PC as signal-source.
On a resolution of 640x480 at 60Hz all things seem to be fine ( with the maxed-out Hor-Phase control out of mind :-/ ) .
But with 800x600/60Hz or even 1024x768/60Hz the same problem occours.


Whats going wrong here? Hours and hours of fiddling around with all those controls, reading the installation and service-
manuals over and over angain, didn't get me even a little bit closer to a solution.


Thank you very much in advance! It would be so nice, to get this set working after all

With best regards,
Matthias

[arbey]

Hi Matthias,
do you have a rcvds or the little white box (that hooks up on the back) connected
to the barco?
About the horizontal lines, maybe your G2's are set up way too high.
Can you get the internal crosshatch pattern when you turn the swith video/internal
crosshatch?

regards

[matze584]

Hi arbey!

I have the small white box fixed directly on the back of my Barco.
Ahm. For the horizontal lines you are talking about
Please don't miss-understand me. I don't think, that the scanline problem is caused by
wrongly set G2-Voltages, because it is possible to get a well colored image by modifying the
video-timings ( to get the picture out of the scanlines start after retrace).

The crosshatch-pattern generated internally shows up the same problem as the external source does.
It shifts more and more to the left, the higher the frequency is set.
On the 64kHz setting the pattern even wraps around and reenters the scanning-area on the right.
This can be made even more noticable, if the horizontal-phase-control in the white box is set away from
its "maximum-right" position.


Greetings!!
Matthias