CurtPalme.com Home Theater Forum

pm · Joined: 23 Aug 2010 Posts: 85 Location: Hants UK

Is a general phrase I'm reading time and again. i.e. the lower the better.

Am I reading this correctly or is this an oversimplification?

My Barco 1209s has hand written labels on the neck boards saying "special mod." Any idea what this alludes to? Other models appear to have numeric G2 settings to compare with but the Barco doesn't.... unless I'm missing it?

As it happens, if I use the G2 menu and adjust the relevant pots to trim to the point at which the LED goes out..... they have no effect at all! Perhaps that is a result of this "special mod".... or maybe not... perhaps just coincidence...

As a result, I've had to reset the G2 settings by eye and a test card with colour ramps... it looks OK with natural skin tones and grass/sky looking very natural.... but that's as scientific as I've got it. How can I refine this?

Cheers,

Paul

**Curt Palme** · Posted: Tue Jan 21, 2014 1:50 am Post subject:

The 'mod' is most likely a shimmed tube internally, suitable for very curved screeens. If you have corner focus issues, then that's most likely due to a shimmed tube. It was a real issue with plain 1209 sets, but luckily with the Scheimpflug adjustments of the 1209s, you can overcome most shim issues with that.

What's the hour counter on your chassis? If the tubes are original and the chassis has over say 15,000 hours on it, there's a chance that emission has dropped off that even max G2 settings won't allow those LEDs to go off. Also, you need to turn the G2 controls VERY slowly to see the G2 LEDs wink off, it's a very narrow window. Turn the pots too quickly and you'll never see them blink off.

SOmetimes though, a bad AKB circuit won't allow the G2 LEDs to turn off. You could have a bad video board or neck board, but if the colors are correct and the set looks good, I wouldn't worry about it!

**Curt Palme** · Posted: Tue Jan 21, 2014 1:51 am Post subject:

Oh, and a new tube in a 1209s will usually have the G2 trimpot at about the 1/2 way point or so. A lower emission tube will have the G2 maxed out, but chances are a tube like that will still have usable emission for years.

pm · Joined: 23 Aug 2010 Posts: 85 Location: Hants UK

Thanks Curt,

Ah, that's interesting..... I do have corner focus issues .... mainly all down the left side with the blue tube and I can't take it out with the Scheimpflug...

The chassis reports 11600 hours. Who knows with the tubes? The guy I bought it off was big on the CRT scene over here but seems to have gone completely off radar over the last couple of years. He undoubtedly swapped out tubes and boards on this machine... lots of hand written labels all over the place!

I'm looking to re-tube soon.... will these shims be obvious if they're fitted? Will I need to do anything to the neck boards with new/different tubes?

I'll investigate the G2 trim later..... it's early hours here....

Cheers,

Paul

**Curt Palme** · Posted: Tue Jan 21, 2014 2:39 am Post subject:

Andy? Mad Mr H?

I don't know if I ever pulled out a tube out of the housing from a modded tube, but I'll bet that one edge of the tube is set higher than the other one. I'm sure the mod can be undone as well.

pm · Joined: 23 Aug 2010 Posts: 85 Location: Hants UK

A chap by the name of Roland..... Maybe he went by a nickname on the forums? Nice chap, very knowledgeable..... showed me the convergence capabilities of his 909... so impressed....

Bit of a loss to the cause. Sad

**Curt Palme** · Posted: Tue Jan 21, 2014 3:18 am Post subject:

Yes, he's been here in the past. Andy was another member that knew CRTs quite well, but dropped out of the forums 3-4 years ago. Not sure what the deal was with Roland..

pm · Joined: 23 Aug 2010 Posts: 85 Location: Hants UK

I suspect domestic upheaval..........

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

pm · Joined: 23 Aug 2010 Posts: 85 Location: Hants UK

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

Clockwise is full

Ile · Posted: Wed Jan 22, 2014 10:36 am Post subject:

Those leds doesn't always work like they should.
I just ignore those and adjust G2 by eye.

Project a video black image.
Set the projector to D6500 in the color menu.
Set brightness to 50 and Contrast to 0.
Look into the tube and turn the G2 pots until you can just see the raster lighting up. All colors to same level
Final adjustment should do to warmed up projector.
Final tweaking can be made with color menus custom black level adjustment.

One cause is in attachment or leds calibration pot could be drifted.

pm · Joined: 23 Aug 2010 Posts: 85 Location: Hants UK

Thanks Ile,

I haven't tried doing that by looking directly at the tubes, but I think I do much the same by putting up the colour ramps and turning the pots up/down until I can just see all the ramp gradations in each colour. The results of that seem quite good.... natural looking skin etc etc.

I'll give it a shot and see! Smile

I compared that service sheet to the 1209s service manual and it appears that the 1209s had already incorporated that mod. Thanks for the info anyway!

Paul