Wobbly screen on a NMS 8220

By MichelM

Expert (80)

Аватар пользователя MichelM

25-09-2015, 22:05

The screen of my Philips NMS 8220 is a bit wobbly. It's connected through SCART, and I know for sure the SCART cable and the monitor are just fine, because if I connect a NMS 8245 (or any other MSX computer) using the same cable and monitor, I do not have the issue, so the issue must be with the 8220.

On the 8220, when I start up the computer, everything is just fine and the screen is perfect, and then after about 10 seconds, the letters on the screen become wobbly, and sometimes, I also see a flicker on the screen. And it just keeps on doing that. Each time I shut down the computer, and restart it, then it's fine for a few seconds, and then it becomes wobbly again.

I cleaned the entire computer inside and out, used contact spray on all connectors, but the issue doesn't go away. It remains wobbly.

See a video here: https://youtu.be/8mbaPiUDSEM

Has anyone ever experienced this before, or anyone that knows how to solve this?

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By Manuel

Ascended (18082)

Аватар пользователя Manuel

25-09-2015, 23:10

Bad capacitor(s)?

By MichelM

Expert (80)

Аватар пользователя MichelM

27-09-2015, 18:02

Any other ideas what this could be? Or should I do that first, replace the capacitors?

By Grauw

Ascended (10010)

Аватар пользователя Grauw

27-09-2015, 18:19

Yeah, it's also my guess.

By Metal_Geart

Expert (73)

Аватар пользователя Metal_Geart

28-09-2015, 19:47

Hi MichelM.
I experience the same issue every now and again with my VG-8235 (SCART with monitor).
I'm sorry to say that I don't know its cause or have a decent fix, but perhaps just some more clues for you or another user.

In my MSX the problem seems related to the cartridge ports.
Anytime I plug in a random cartridge in a random port the wobbling can be there.
I just try a number of times and eventually it will be allright.
Another weird thing: The startup screen (MSX) is never wobbly! Only the basic- and game screens etc.

I'm interested to see if anyone can make anything out of this.
And also in a fix ofcourse :-)

By sd_snatcher

Prophet (3453)

Аватар пользователя sd_snatcher

28-09-2015, 21:49

Quoting myself from this thread.

It might be an issue with the CSYNC signal. Try googling for a "sync cleaner" circuit, and build one yourself. It's pretty simple and only basic soldering skills are necessary.

By Grauw

Ascended (10010)

Аватар пользователя Grauw

28-09-2015, 23:08

Metal_Geart: Maybe the power supply gets instable under load? Or caps.

If the sync signal is bad due to the above issues, it may depend on the contents on the screen whether the screen can still keep sync (which would explain why it does not happen always).

What sd_snatcher refers to (I think) is that some MSX computers output a composite-sync in stead of horizontal-sync. It’s a different thing, the output is actually nominal, but I think not all displays can deal with it very well. Though I’ve never had issues with this myself, some displays may have trouble…

By Lord_Zett

Paladin (807)

Аватар пользователя Lord_Zett

28-09-2015, 23:03

Realy easy solution. Dont use a lcd/tft.

By MichelM

Expert (80)

Аватар пользователя MichelM

29-09-2015, 05:50

Well, you know, my NMS 8250 and NMS 8245 work just fine with the same LCD monitor, only my NMS 8220 is having a wobbly screen. So I think using a LCD screen should be just fine.

I actually discovered today that if I unplug the SCART connector on the computer and plug it back in, then it will be fine for about 10 to 20 seconds, and then it starts again to become wobbly. I have yet to try it with a RGB (DIN8) connector, and see if that makes any difference.

By Lord_Zett

Paladin (807)

Аватар пользователя Lord_Zett

29-09-2015, 16:02

on scart its rgb. av (din8) is the other option. you should try it on a crt. i got some tft/lcd and not all can handel the msx's. even on that makes the lines jump over the screen.