CRT horizontal blur

[xphanoo]

Hi,
I got a Philips flat screen CRT recently, and it has a picture sharpness problem. There seems to be some horizontal blur happening (see on the picture, vertical lines appear blurry but not the horizontal ones).
I tried to adjust the focus pot inside but it's already at its optimal setting. G2 is adjusted to the correct value according to the service manual.
Checked a few caps (not all) and reflowed a few solders, didn't help with the issue.
Also the image is slightly pulsating in the upper left corner (not the 60hz flicker but it's like slightly vibrating at a slower rate)

Do you have any ideas on what to do ?

[Guspaz]

What’s your source? What cables are you using? That sort of blur is normal for early SNES revisions, for example.

[xphanoo]

I'm using a Megadrive through SCART (RGB), the blur doesn't come from the console or the cable because I use it on another CRT and the picture is perfectly clear

[xphanoo]

Or maybe that TV is using the composite signal from the SCART instead of RGB ? I don't know how I can verify this.. It's a philips 21pt5401

[xphanoo]

I noticed the OSD has the same burry quality so it doesn't come from the video input. Is it possible that the components driving the electron guns are slower due to their age and don't turn on/off as quickly as before ? Would some capacitors be responsible for that ? (and if yes, which capacitors since there are a lot of them on the board...)

Found the service manual : https://elektrotanya.com/philips_21pt54 ... ad.html#dl

[Josh128]

Appears to be something in the video / gun drive circuitry. You spoke of caps, did you change the ones on the neckboard? Thats where the video drive amps are located. Looks like turning on from black, and transitioning from one color to any other but black is smearing/trailing, indicating that the guns are not turning on/off fast enough and/or there is some "leakage" in doing so.

[buttersoft]

Those smear lines are on white horizontals, which is all colours. Power supply or neckboard problem, would be my guess. Screen cap might be going?

Does this look familiar?
https://youtu.be/ebOmWYqlOIY?si=-3L8yMuJmuBXaiLx&t=70

[xphanoo]

Kinda, although not as extreme. I found a topic with similar issue they solved it by replacing a resistor on the neck board : https://www.arcade-projects.com/threads ... ing.15263/

My neck board is fairly simple :


I changed the only electrolytic cap on that board, and it improved sharpness a bit.
Before :


After :


Although the picture is still smeary in overall, for example here is what the 240p test suite menu looks like :


Readable but not as defined as my other CRT TVs (i have two small 36cm and a 68cm that are perfectly fine). This one is a 52cm CRT.
I'll try changing capacitors around the video IC and checking the resistors on the neck board

[Josh128]

I think you are on the right track. If you could set up a test image with some vertical bars of R,G,B transitioning to black, you could see if the issue is on a certain color gun to further narrow down the culprit.

Also, I must say, that recap on the neck board looks to have improved sharpness by a lot, not just a little bit, lol.


****EDIT: Compared to my XS955, that neckboard is ULTRA simple. I mean, you could literally check all the individual resistors and diodes and non-electrolytics in a trivial amount of time. Definitely worth doing. Those are some mighty small transistors on the neck board-- not 100% sure they are for the RGB drives or if they would be located on the main board. If you can find a service manual, you should be able to narrow it down.