CurtPalme.com Home Theater Forum

[roland@b4]

Help this is driving me insane.
I have two identical bg1209s machines on the bench side by side but one of them has an intermitent flicker on blue on very low light pictures. The best test I have found is the end credits.
The effect on screen is very similar to the light a (blue) candle would give blowing in a breeze just oocasionally making the blue image a tiny bit brighter.
On full bight 100% the image is stable. as it is 90-30%. If I turn the contrast right down and the brightness to just make the raster glow it is the same effect.
My thoughts was that this was a G2 oe EHT issue but remeber this only affects the blue.
So here is what I have done so far each time swapping the boards from one projector to the other. Each time the issue remains on the same projector and will not transfer!
SO Ihave Swapped
Blue tubes complete with scan and focus electrics
Tube end amplifier
Blue and green video connectors on tube amp
Blue and Green voltage /g2 connectors to tube amp
G2 boards
Power supply
Quadrupler
Changed output connector on splitter
Changed splitter
Disconnected Red and Green EHT leads and RGB amps blue still flickers
EHT reg module
Scan reversal boards
Complete convergence trays

Anybody come across this before
many thanks
Roland

[secstate]

I once had this on a Barco Data 808s with new P16 tubes and 120MHz neckboards from as 1208s. In my case it showed up on all three tubes (I would check closely but I bet it is there on all three tubes). Like you I pretty much replaced everything including the whole HV/EHT section. I could never get to the bottom of it. I also had a 1208s/2 at the same time that exhibited the exact same problem. The solution for me on my Data 808s in the end was to put back the 75MHz boards and the problem went away. I know several other people who have had the candle flicker effect and did not get to the bottom of it. However a month or so ago somebody else posted a similar problem and Ile said it might be caused by ABL. Sure enough when the person turned off ABL the problem went away perhaps this is your issue? See http://www.curtpalme.com/forum/viewtopic.php?p=191269&highlight=#191269 . I moved on to a 1209s that does not exhibit this problem so I never tested the solution.

This could also be a short in the tube but you said you swapped the tube so I am assuming you have confirmed the tube is ok.

[roland@b4]

I'm sure it is not the tube as have a spare blue and that does the same.

I've looked very closely at the R & G they are very steady

I have now changed the controller boards over no difference

I cant see a way of disabling the ABL on a BG1209s as it is all on the RGB amp

I have just changed all three RGB amps no difference.

[Curt Palme]

Try putting the R or G tube into the blue location. blues seem to flicker most, I've seen this in planetariums before. Make sure your spare blue doesn't have the same issue.

[Curt Palme]

Try putting the R or G tube into the blue location. blues seem to flicker most, I've seen this in planetariums before. Make sure your spare blue doesn't have the same issue.

[roland@b4]

OK this is getting silly now.

I replaced the flickering blue with a red "RGR"
Steady as a rock no matter what the G2 or brightness I get no flicker

I have replaced all the tubes with blue tubes. "BBB" they all flicker

If I put any one of these blue tubes in the other projector no flicker so its not the tubes

I must have missed something.

What are my chances of doing a tripple stack with three projectors each with the same coloured tubes in? RRR GGG BBB.
If it is effecting all three tubes it must be in a common area like SMPS or EHT G2. ( I VERY carefully swapped over each component with the other projector it would NOT transfer)

At least I know its not the mother board or my BBB set up would only have effected one channel. It does show that the blue is more sensitive

Thanks for your help

[r.bauer]

Did you adjust the G2 after swapping Blue in all chassis'.

Is G2 stable, or does it need re-adjustment from time to time?
Did you take out the convergence drawer?

I had a similar issue a long time ago, only two chassis, but the same result. Problem disappeared after 40-50 hours of watching. Has the projector been in storage for a long time, or has not seen any use for a long time?

[roland@b4]

G2 was reset each time a tube or eht component was changed. Very easy on a 1209s

Once set G2 is stable only rechecking when a new source or calibration required.

Flicker is present with convergence draw in or out

Yes projector in fact both have been in storage for a year. Nice dry warm conditions (UK remember) But has run at least a day or two since with no improvement.

I did work with Barco on a fix for a BG808s that was doing this but very clearly on all three colours about 3-4years ago for the life of me I can't remeber what it was we did. It was a small mod to the RGB amps.