CurtPalme.com Home Theater Forum

[KrisRoberts]

Okay, so discovered something new with my franken G90 project today.
Sigh.

When the projector starts up after being off for a while there is a pattern of horizontal lines that move in a cycle up and down across the screen - mostly visible only on low IRE areas. I noticed it when I powered it on and went to the Bias adjustment to check what I had been doing in the last session - and saw the lines very predominantly.

Looking at other signals and test patterns it appears to happen regardless of whether its an internal pattern or an external signal. The same pattern of lines presents on all thee tubes.

Once the projector has been on for a few minutes it seems to settle down and I haven't seen it happen again once it stops.

Its hard to photograph because it only happens on dim parts of the image and the lines are moving, but you can kind of see it here with the brightness cranked up on the Bias pluge pattern:


Here's a sad attempt at a video in which you can also sort of see the issue but not clearly.
G90_Startup_lines_02.avi

At this point I'm probably going to give up on the hybrid projector using most of the parts from the machine I picked up last week and go back to using pretty much everything from my old projector with the new YA board. And then just prey whatever caused my issue with the old YA board doesn't kill this one... But I figured I'd post about this just in case someone knows what might be going on.

[CIR Engineering]

I can't see it in your photo or your video

However, I think I have seen the same thing you are describing before on a unit that I have here. I built this G90 out of scraps from three G90's and figured it was due to me improperly running wires or a mix and match of parts. I don't care that it does this because it is just my test chassis for diagnostics and tube break in. I have never bothered to really figure out what the cause is.

As I said in the other thread, it can be a beast to mix and match a lot of parts with a G90. I would go back to your original G90 with the new YA board. Your YA failure was almost certainly not due to the projector, it was a problem on the YA board its self I think.

craigr

[KrisRoberts]

Yeah, I can hardly see it in the video/pic and I know exactly what I'm looking for.

I'll revert back to the old configuration this morning and see how that goes.

Last night I restored the new machine so that its currently using all of its boards - none from my old projector. But it does have my tubes and focus coils. The startup line problem still presents.

Its sad because there are a number of things with my old projector that were a little quirky that dont seem to be present on the new one but oh well...

EDIT
So yes, once I swapped the chassis and re-assembled the old projector with just the YA board from the new one - all is well. Whew. Now back to setup joy.

[CIR Engineering]

[KrisRoberts]

Nothing too terrible.

1. The rectangle of flashing lines. I know you guys are reassuring that an IC on the YA board went bad on its own. But without a clear diagnosis of which components went bad and a viable fix I tend to be paranoid. If I could avoid putting a working YA board in a machine where one already went bad, I would do that.

2. Drama changing inputs/resolutions. Particularly with the PS3 which feels the need to change resolutions many times before starting a blu-ray it can make the projector go haywire and not sync for a few seconds. I dont think its really doing anything terribly bad, but it freaks me out a little. The new projector seems to snap right away and it always seems to lock to the new resolution right away.

3. A little red convergence drift. I often check after watching a movie and find that red is off a little (never more than one or two coarse clicks to re-adjust). I'll adjust it. The next time it starts up cold, red is quite a bit off and as it warms up it gets better but never seems to go back to exactly the same place from the previous time. I was really hoping to see whether it would drift at all with the new projector.

4. My blue tube goes through fits and spurts where it doesnt go all the way black.
http://www.avsforum.com/avs-vb/showthread.php?t=1135866
I know that its in the tube and putting that tube in the new projector didnt change anything, but just listing the issues I have.

[CIR Engineering]

The only one that seems a little abnormal to me that isn't explained is the amount of red drift.

JohnHW learned from an engineer in Japan that the lenses can have this affect. I don't recall the details, but he had the same problem and the engineer had told him something about the lenses needing to remain with their original tube. I know it sounds hokey and I can't explain it, but he methodically tried each lens on each tube until he tried all nine possibilities. He found one combination that held convergence much better.

I had heard this story from John and actually had the same issue with red drift on my home G90. I did the same thing with trying the lenses on each gun... And I to found a combination that holds convergence better.

I have no idea why, but you might want to try it.

craigr

[AnalogRocks]

Now there's the Voodoo

[AnalogRocks]

Now there's the Voodoo

[stefuel]

[CIR Engineering]

It doesn't make sense to me either, but I am just passing on what John was told and verified, and what also cured the red drift on my own G90. My other question is what happens if you replace the lenses...

I seem to recall that John's source said something about over time the lens and housing start to match each other or something. This was like 4+ years ago on avs and I don't recall the details. John had a multi page thread going when he was trying to track the problem down for more than a year. He tried sooooo many things. And in the end the lens swapping did it.

When I had the problem on mine I went straight to lens swapping because I knew that I had mixed them all up and hadn't kept track of which lens when on which color.

craigr

[ecrabb]

[CIR Engineering]

[CIR Engineering]

On the G90 (and I think the G70 if I remember correctly) the HV cable orientation coming off the red tube is on the opposite side of the tube as compared to green and blue. In other words, the red tube is upside down compared to the blue and green tubes. I have long been curious if this could have anything to do with why red is always way out of convergence on the G90 and G70 before they warm up. Usually on the G's the green and blue are not bad when the projector is cold, but red always starts out about two solid clicks higher than the others and then drifts down when the projector gets warm.

I have been thinking about doing this for a long time, but the next time I put a new red in the projector I am going to flip it to match the green and blue so that all three have the same orientation. I've actually got a full set of new tubes for my G90 here, and if I had an extra housing right now I would try it next week... just to see.

I usually have an extra full set of G90 housings, but they're all in use right now with new tubes mounted in them Sony style. They are prepped for a retube on one of my client's G90's this December. I went ahead and mounted the tubes early because I figured if I get a G90 retube on the schedule before December, I would just use these and then mount another set for my scheduled client. Now I wish I had another set of bellows.

Anybody got one tube housing for a G90 that I can borrow?

craigr

[jarseneau]

Is the RED neck board made upside down as well?

[CIR Engineering]

[KrisRoberts]

I am using the lenses which came with the projector I got last week as they are a lot cleaner on the inside than the ones I had been using. I'm pretty sure the old ones were randomly put on as they were sent to me separately and had no indication of which one went to which tube. The newer ones are marked and I did keep them on the same colors so we'll see if there is any significant difference.

[dvh99]

the lens story is odd, i removed the lenses when changing out the bellows but didnt keep them all on the same colour, guess what, no convergence drift.
the only thing i can think of is that the material of the lenses is somehow changed due to radiation, but to cause drifting??