MSX2 AND MSX2+ VIDEO PROBLEM

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By giuseve

Paladin (753)

giuseve's picture

23-05-2014, 21:15

HALLO !!
I've three video output solutions: Samsung HD 30" LCD TV, Philips FullHD 22" LCD TV, Input USB card for my PC
I've tried my VG-8235 on all this solutions, having some problem with some rom (fo example, muffie's conversions from coleco) and havig strange colors on my PC.
Now I bought a NMS8245 expanded to Plus with a V9958. Problems are worse: Samsung is in a dancing time with stange blends, Philips seems to work .. and after 10 second it stops. On the PC the best solution i've obtained is a greyscale, but when i try to load muffie's stuff... video output disappeared.
I' ve tried also with:
VDP(10)=VDP(10)OR2
VDP(10)=VDP(10)AND253
VDP(10)=0
screen,,,,,1

in various combination with no results.

Any ideas ? Have I to come back to RF output abandoning the scart output ??
Why have I to do this? :-(

I need Help !!!

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By Grauw

Ascended (10681)

Grauw's picture

23-05-2014, 21:52

Maybe your SCART cable is bad? Have you tried another?

I think it would help diagnose the problems if you’d post some pictures or video.

p.s. You definitely want to try and get SCART (RGB) output to work… I connected my CX5MII through composite video and it looked horrible, pixels dancing around the screen like crazy, whereas the RGB image was laser sharp (even sharper than razor!).

By giuseve

Paladin (753)

giuseve's picture

23-05-2014, 22:30

I've tried 6 different SCART cables.
I've also tried to press H while booting. The strange thing is that it worked one time only.
When I run a demo it starts to dance again.
Then I try to reboot with the H-key trick ... and it didn't work anymore.
How could it be possible ???

By Grauw

Ascended (10681)

Grauw's picture

23-05-2014, 23:59

Make some pictures or video with your phone Smile, then it’s easier to see what you’re talking about exactly. Some people have a lot of technical knowledge on this forum and I bet they could help to identify the problem if they could see it.

I don’t know what you mean by “dance” (why I ask for photos / videos), but, SCART cables contain both RGB and composite video. If the RGB isn’t getting through for some reason (e.g. cheap thin cable, or TV doesn’t support it), then it will revert to the composite video signal.

By giuseve

Paladin (753)

giuseve's picture

24-05-2014, 10:35

@Grauw
Many Many thanks for your attention. I've just tried with another cable given by my neighbour before to give up. It's less thin than mines and.... it seems to work !!!
Now I see my MSX without problems... Maybe I have to buy a SCART cable with gold connectors, quite short and using almost the same money I spent to buy my MSX.
Anyway, with ANT Demo (I'm using it to test), after 5 minutes, the problem appears again. The situation It's better than before, but It would be nice to resolve it definitly.
I'm thinking that the demo probably push the V9958 to the limit and it becomes hot after minutes. Do someone think it could be the right reason? If yes, are anywhere instructions on how to make a personal cooler for the VDP?

Regards

By Manuel

Ascended (19220)

Manuel's picture

24-05-2014, 11:41

I don't think that is the reason. I've never heard of weird output because of the VDP becoming too hot. Is the problem gone after a reset and when you run it again, it appears at the same place? A video of the effect would be very helpful indeed.

By giuseve

Paladin (753)

giuseve's picture

18-06-2014, 19:53

i was thinking about this.
2 years ago in Italy we used the old TV Broadcasting system. My SAMSUNG LCD so has a built in ANALOG RF Sysntonizer!!
So I've tried to connect my MSX 8245 2+ via RF cable switching the TV to the analog mode.

I have the same video problems of instable image and flickering with strange colors.
But now if I use VDP(10)=VDP(10)AND253 the video goes OK.
The problem is that the first program that change the video frequency makes my trick unuseful.

I think I would look for a RF syntonizer for my PC to solve this: I can't buy an analogue monitor deu to space provblems in my house.

Any ideas?

By giuseve

Paladin (753)

giuseve's picture

18-06-2014, 19:54

Is it possible to fix my MSX2+ VDP to be nmore compatible?

By maxis

Champion (512)

maxis's picture

18-06-2014, 23:02

giuseve wrote:

Is it possible to fix my MSX2+ VDP to be nmore compatible?

Hello,
Since 9958 is not a pin to pin compatible replacement of 9938, you have an improvised circuit inside you NMS. 9958 uses separate analog and digital power supply rails when v9938 does utilize a single VDD source for all its functions. A typical solution floating on the internet - linear +5V regulator on the 9958 DAC powered from +12V rail.
If this improvised voltage regulator on the output analog stage is getting hot, it goes into the thermal shutdown on the high brightness image.
Result - partial loss of image, loss of sync, but the SW/FW functionality of 9958 is intact.
So, please, open up your machine and take a few zoomed images around the VDP.

By Daemos

Paragon (2020)

Daemos's picture

19-06-2014, 09:47

Had similar problems on NMS8255. Solved the problem by adding a filter between pin6 (sync) and mobo I believe it was 100K/.1uF in parallel. I believe i posted the solution a long time ago on the forum. Let me find it for you.

EDIT: had the problem before I joined MRC so no record. Basicly what I did was cutting pin 6 and trying different filter combos until the colors where perfect. Never had any problem after that. It seems that the V9958 is somewhat more noisy on the sync output when the power supply is noisy as well. The filter is quite capable of taking the noise out. I remember now. The combo was 10K/.47uF in parrallel

By giuseve

Paladin (753)

giuseve's picture

19-06-2014, 21:12

@maxis.
So you're saying that the most common way to upgrade my 8245 to plus has the problem of hot temperature? Now that you say this, I noticed that some weeks ago it used to work correctly for 4 minutes and then started to flicker. What about a cooling fan inside the MSX?
@daemos
so you're saying i have to cut pin 6 and weld a cable with a 10K/.47uF to the pin 6 and then to the mainboard where the pin6 was connected?

@maxis @daemos : thanks guys, I think that your explanations and solutions could be very interesting for my problem. I'm not so able in welding. Can you help me with some image ore something like that?
Tomorrow I'll open my NMS-8245 to take photos to show you and a movie of the video problem. Thanks again guys, I was almost giving up with my problem !!!

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