TFT screen shimmers and goes blank

[JohnD]

I have a Radeon 7500 AGP4 card

Display settings are 800 x 600 pixels, 32 bit colour

I have changed Refresh rate to 70Hz(all others shimmer worse, or are unviewable)

Shimmer seems worse on some pages than others

Display was formerly OK but has recently been shimmering more and more, and in the last few days display goes blank when unattended (like going to a blank screensaver, but I have none) and will not come back with mouse or keyboard, but will come back if I turn screen or PC off and on again a few times

Some colour pictures have specs or patches or incorrect colour

I have uninstalled the driver and done the troubleshooter

What should I be looking at next?

 

[Goldberg]

Have you checked that the VGA lead is connected securely?

If the symptoms are the same with a different monitor, then the Radeon card is either partially unseated or is faulty.

 

[JohnD]

1) yes

2) no spare monitor but will try unplugging the card

thanks

 

[JohnD]

I took out the AGP card and am running on the SIS on-board video.

After everything had been switched off while I was tinkering, it seemed OK, but has got worse as it all warms up.

It still shimmers but it has not gone blank in the last day or two (when it did, I tried turning the screen on and off a few times with its power button, and it usually came back after a few tries.

Text is poor, a bit like looking at output from a 9-pin impact printer, and has been getting worse while I type this.

I tried changing refresh rate, it is now best on 60Hz. When I tried changing screen resolution, which also made it sort of run sideways, it is now back at 800x600 which is as good as I can get. I am on 32 bit colour.

I am getting pale green wiggly lines running diagonally across the screen.

For some reason, it varies from a bit better to a lot worse over time. Internet Explorer seems worse than most

I think I will unplug the screen and take it to a friend's house and see if I can plug it into their laptop, so see if it is the screen at fault.

I foolishly ordered a replacement AGP card before doing this trial

The TFT screen is badged "Exair" and has some settings I can change with buttons on the front, including phase and clock, but I don't know which ones I ought to try

 

[Goldberg]

I took out the AGP card and am running on the SIS on-board video.

I recommend not doing that.

I tried changing refresh rate, it is now best on 60Hz.

It should always have been on 60Hz.

I think I will unplug the screen and take it to a friend's house and see if I can plug it into their laptop, so see if it is the screen at fault.

I foolishly ordered a replacement AGP card before doing this trial

The TFT screen is badged "Exair" and has some settings I can change with buttons on the front, including phase and clock, but I don't know which ones I ought to try

I recommend borrowing a known-to-be-working monitor to see if that works with your computer. That will tell you whether the fault is in the monitor or in the computer.

 

[JohnD]

I took out the AGP card and am running on the SIS on-board video.

I recommend not doing that.

why not

I don't think I can borrow another monitor, but I think if I take my monitor round, I can get other people to try it on their PC. Won't that do?

I have an old CRT screen in offsite storage, I can bring that home and try it. Or does it have to be another TFT?

 

[EddieM]

it does rather sound like the TFT's shot. but of course try the usual diagnostics / tests, to see which component is causing the problem. LCD's should be set at 60Hz, the refresh rate is largely irrelevant with a TFT. i.e. due to their nature, they don't flicker.

 

[JohnD]

try the usual diagnostics / tests

what they?

I have a thing called "Checkit" that came with Norton Systemworks. When I run it its "Graphics Test" it says all tests passed, but some of the displays didn't look right - sort of flashing or zigging across the screen.

"bitmap stretching" looks wrong
so do
bitmap drawing
flood filled drawing
pixel drawing
string drawing zooms up and down to fast to read
bitmap scrolling is blank

 

[EddieM]

putting the TFT on a known "good" system, with the refresh rate set @60Hz would be a good start. Putting a known good TFT on your system. Take it from there.

 

[Goldberg]

I took out the AGP card and am running on the SIS on-board video.

I recommend not doing that.

why not

Because in the time you've spent doing it you could have tried a different monitor, and because trying a different monitor is the best approach with this problem.

I don't think I can borrow another monitor, but I think if I take my monitor round, I can get other people to try it on their PC. Won't that do?

No. You will still have a non-working PC-and-monitor combination, and won't have moved forward in finding the cause.

I have an old CRT screen in offsite storage, I can bring that home and try it. Or does it have to be another TFT?

Trying a CRT would be a start.

If you have your mind set on taking your TFT somewhere, then take both PC and TFT to PC World (yes I know) and get them to connect the TFT to one of their machines, and then buy a new TFT from them and test it on the spot. If you don't have a PC World nearby, then find a local PC retailer who is willing to do the same thing.

 

[JohnD]

but I had a screwdriver handy, and I didn't have a spare screen!

curiously, I poked the buttons on the screen, and found an "auto adjust" option. I have done this a couple of times and the picture is certainly a lot more stable. I don't see why it had got out of adjustment. If it keeps going off I will see if my neighbour will let me cart my great heavy tower over the road and try substitution. My local supplier is Novatech and I see they offer a 3-year onsite warranty on a 17" or 19" screen if I need a new one.

 

[EddieM]

but would you take your car engine apart if it wouldn't start, without first checking it had petrol in it

 

[JohnD]

It took me a few mins to take out the AGP card

last time I took an engine apart it took me days

 

[JohnD]

I have done a bit more tinkering (using the tools and materials that are to hand) and the display is definitely a lot worse when I put the AGP card back, and is better on the SIS on-board graphics, so I am using it on that for now. At the moment it isn't shimmering (I have made the screen auto-adjust itself again)

The refresh rate set itself to 56Hz, when I tried changing it to 60 it flickered badly, and at 72 it was fuzzy.

I already have a new AGP card on order, and will try substitution after that.

Thanks for help and suggs so far

 

[Goldberg]

It took me a few mins to take out the AGP card

Indeed, but it didn't fix the problem, nor did it eliminate anything from suspicion. Strictly speaking, that was a waste of a few minutes.

In addition, opening the case creates a risk of anti-static damage - did you use a wrist-strap, as would have been suggested to you if anyone knew that were going to open the case?

In addition, removing and re-inserting cards results in wear on the AGP socket, so it's best avoided.