CurtPalme.com Home Theater Forum

dave148 · Joined: 15 Feb 2011 Posts: 33 Location: Colorado Springs

I cross posted this at the avsforum. I hope that is okay.

When we turned the projector on Sunday, the red gun had lost its
left keystone setting. When going in to try to re-adjust, it allowed the
number to be changed, but there was no effect on the image. I did a
weak convergence fudge by skewing the red gun as far as I could in
the problem area, then adjusting back the remaining part of the image
with keystone on the other guns, zones, etc. But the red gun zone 18
would not move when I changed the setting.

from the theory of operation manual and the service manual,
It looks like the DB board, signals X9, and KL are for the zone 18, and
left keystone respectively, so perhaps this board has some sort of problem.
But other than being on the same board, it is not clear if there is anything
consistent between the two failures.

The projector is about ten years old, so after reading other threads about
the Dallas part on the YA board, I should probably replace that, but
no power has been removed from the projector recently, and the
symptoms don't sound similar to others' reports on this part's failure
anyway.

Any ideas?

**Curt Palme** · Posted: Tue Feb 15, 2011 1:16 pm Post subject:

It could be a bad convergence board, but it could also be a bad YA board:

https://www.curtpalme.com/forum_archived/viewtopic.php@t=25504.html

dave148 · Joined: 15 Feb 2011 Posts: 33 Location: Colorado Springs

Curt Palme wrote:

It could be a bad convergence board, but it could also be a bad YA board:

https://www.curtpalme.com/forum_archived/viewtopic.php@t=25504.html

It sounds like the convergence of his image was actually changing while he was looking at it.
On our G90, the convergence took a step change, and now at least two of the convergence
methods for the red gun are not working.

**Curt Palme** · Posted: Tue Feb 15, 2011 1:52 pm Post subject:

Right, but that unavailable IC421 has failures in many forms. All commands going to boards come from that chip. THe only way to check is either to board swap, or send me the convergence and Ya boards for testing, as I have a working G90 here.

CIR Engineering · Posted: Tue Feb 15, 2011 2:39 pm Post subject:

My educated guess is that this is NOT IC421. I have seen failures like the one you describe a few times and it has always been an issue on the DC board.

I have a spare here that I could sell, but see if Curt has one first as this is his forum Wink

In any event, I would probably just replace this board rather than track down the problem because these boards are not usually hard to find...

If IC421 were bad you would most likely have no geometry controls at all. Usually when IC421 goes bad all geometry controls run wild executing commands all over the place making the image jump everywhere along with other symptoms like brightness and contrast going up and down wildly. Or none of the geometry controls work at all and things like brightness and contrast do not have an affect. Usually when controls stop working due to IC421 they all stop at once and the problem happens instantly not gradually (all controls fail the same instant, not one one day and another another day).

Try adjusting brightness and contrast and verify that adjusting them works.

I think this is a simple repair and you will be fine Smile

craigr

**Curt Palme** · Posted: Tue Feb 15, 2011 2:54 pm Post subject:

I do have a DC board here, but it's best to send your boards up to verify the problem. Let me know if you want to send them in.

CIR Engineering · Posted: Tue Feb 15, 2011 3:06 pm Post subject:

dave148 · Joined: 15 Feb 2011 Posts: 33 Location: Colorado Springs

dave148 · Joined: 15 Feb 2011 Posts: 33 Location: Colorado Springs

**Curt Palme** · Posted: Tue Feb 15, 2011 4:31 pm Post subject:

Email me at curtpalme@shaw.ca.

Thanks!

CIR Engineering · Posted: Tue Feb 15, 2011 5:00 pm Post subject:

dave148 · Joined: 15 Feb 2011 Posts: 33 Location: Colorado Springs