CurtPalme.com Home Theater Forum

alb_qwerti · Joined: 30 Sep 2008 Posts: 54 Location: Italy

Dear Members,

Mechanical adjusting the focus on my pj I noticed a strange thing.

With midpoint focus on 57 and contrast to 80 when I move everything I cannot obtain a good focus on green tube.
1- Center focus
2- Corner focus
3- Scheimpflug

Then I checked the 2pole/4pole rings and the defocused lines and dots are centered/round.

Now the strange thing:
The deflection block is fully against the CRT bulb (correct)
The focus unit is not 8-10mm apart from it (as shoud be and actually is on the R e B tubes) but is fully against the deflection block. To increase the center focus I shoud go even further.

Is there an electronic focus pot for the green tube that shoud be unadjusted on some board?

Thanks for any advice,
Alberto

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

Does the electronic focus work at all on green?
Does the green tube has the exact same part number as the other two tubes?

alb_qwerti · Joined: 30 Sep 2008 Posts: 54 Location: Italy

Hi, thanks for your answer.

The electonic focus is working, with that I can achieve perfect focus all round (with some settings at the end of the scale anyway).
But I would understand what's going wrong with the setup.

The 3 tubes are standard Barco.

Regards,
Alberto

alb_qwerti · Joined: 30 Sep 2008 Posts: 54 Location: Italy

Hi members!

I refresh this old thread because after a new check I found that the tubes, even if Barco labelled, are all different.

R - P19LPB03RJA
G - PT22-30
B - P19LUG03MB

On R and B perfect focus but problem with G.

I have perfect midpoint focus with focus unit very close to the deflection unit, but side focus is very poor.

Where should be the issue?

Thanks,
Alberto

**Curt Palme** · Posted: Sun Jun 14, 2020 2:27 pm Post subject:

If the focus on the face of the tube is perfect, then you may have the wrong lens on the set, if it's designed for curved screens, or the C element has the wrong curve on it.

alb_qwerti · Joined: 30 Sep 2008 Posts: 54 Location: Italy

Hi Curt!

No, the focus on the face of the tube is not perfect, it reflects that on the screen!

The 3 lenses are HD-120

Thanks!

**Curt Palme** · Posted: Mon Jun 15, 2020 1:48 am Post subject:

OK, swap the focus yoke wiring between tubes to see if the problem follows the focus board channel, or if the problem stays on the same tube. If it switches, the focus board is bad, which is the H shift board.

If it stays with the same tube, then the focus yoke is bad (swap that between tubes to confirm), or there may be a problem in the tube (you could switch tubes to confirm that as well).

alb_qwerti · Joined: 30 Sep 2008 Posts: 54 Location: Italy

Hi, already swapped the focus yoke wiring but nothing change.

The PJ is ceiling mounted so is not so easy remove the tubes.
Is it possible swap the yokes between tubes without remove them?

Anyway I noticed another thing that let me suspect that the tube is good.
At 15.7 Khz internal pattern the focus is correct.
More the resolution grow and more the sides are defocused (especially the left bottom corner).

Let me know if the last thing could have any importance.

Thanks!
Alberto

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

I seem to remember that here were threads mentioning that some of the PT22 tubes have a shorter neck than LCP/LUG tubes and they need a different focus coil... please make a search on this here.

alb_qwerti · Joined: 30 Sep 2008 Posts: 54 Location: Italy

Hi Jaky,

I found that old post!
Very interesting but my green tube is PT22-30 and has the same dimensions of the others.

Anyway, to swap the focus yokes you need to remove the tubes?
Should worth a try to swap the neck boards first that is easier?

Thanks,
Alberto

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