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1031q black level instability - any ideas why?

346 Views 7 Replies 6 Participants Last post by Jeepin, Apr 9, 2003

bravozulu

Discussion Starter · Apr 6, 2003

Hi,

I recently bought a 1031q, I've had a lot of fun setting it up over the last few weeks. I'm running the PJ from an HTPC via the RGB2 input, and I'm really happy with the quality of the image. Theres one problem though, the black level setting appears to be a little unstable.

I carefully set the G2 and contrast settings using the methods described on the fantastic www.eboyztoyz.net site, using the Nokia test pattern and Video essentials DVD for reference black levels.

During the last two movies that I watched, the contrast level suddenly changed (over a period of approx 5 seconds), the raster was clearly visible in the projected image and "black" had turned to a washed-out grey. The image could be restored to normal by turning down the contrast level, but after a few minutes the black level had dropped down again, and required the contrast control to be set back in the center for a normal image.

This happened twice in a 3 hour movie. Anyone got some smart ideas as to what could be going on?

Thanks in advance!

Pete

------------------

Sony 1031q

HTPC with Radeon 7500, powerstrip & WinDVD

assorted bits of glue, tape, twigs and cat hair

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Krynos

· #2 · Apr 6, 2003

Could be macrovision kicking in... Have you disabled the AGC on the 1031?

It is a small switch on the left top board (as you look from the back of the PJ --- the board next to the convergence one)

- Rick

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bravozulu

Discussion Starter · #3 · Apr 6, 2003

Nope, not macrovision. I'm running it from an HTPC via the RGB2 input. And the change in contrast doesn't have the predictable cyclic properties of the macrovision artefact. The change simply appears, then returns to normal after a few minutes.

Could it be:

1) A high voltage power supply instability?

2) A problem on the convergence board? (the contrast control is on the convergence board)

If it could be one of these, any idea how you'd check it?

Thanks!

Pete

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Tinman

· #4 · Apr 6, 2003

Try using a bit of contact cleaner spray on the pots first. Then you'll know if you have to dig deeper or not.

Marc

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bravozulu

Discussion Starter · #5 · Apr 8, 2003

Anyone else got a theory? Thanks!

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Kieth

· #6 · Apr 8, 2003

Possibilities: In addition to the above, you could have a bad focus module, bad capacitor, intermittent solder joint, in short- it could be anything. To fix a problem like this will likely require a schematic and setting up a meter to measure various circuit voltages when the problem is and is not present...

--Kieth

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Prometheusbound

· #7 · Apr 8, 2003

Although I own a different brand of projector I had a filter cap go bad in the SMPS. This in turn dropped the 190 volt line that supplies the power for blanking to around 130 volts. It caused an effect very similiar to yours except mine was a hard failure. You might want to check out this supply and see if it is constant.

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Jeepin

· #8 · Apr 9, 2003

I havn't had much experience in troubleshooting my 1031q, but one problem I've had was with the video cable.

I made my own video cable from a 15' VGA extension, cut off the HD15 and made my own SCART cable. My piss poor solder job caused one of the connections to intermittenly lose the green signal input. It would do this without touching the projector at about the same frequency as you describe. It was fixed by actually putting some time into soldering the connections.

Just a thought,

Alan

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