Another problem with RFM, This time graphics on monitor

[Dazzat]

Hello again averyone,
This time I am having graphical problems with my RFM.
To start with I have converted my RFM to a 24' LCD monitor with a GBS-8220 Video Converter CGA/EGA/YUV/RGB TO VGA  and also a sync adapter to covert to 15h video.

What an amazing difference compared to the old tube monitor, would recommend it to anyone.

Onto the bad part... The past week or so the colours on the screen have gone blurry and pixelated



I have checked the LCD on a pc - all OK
Checked the GBS-8220 on a different machine -all ok and tried a new GBS-8220 aswell - still the same
Checked with 2 different Sync adapters - all ok

The vga cables are brand new.

Now I have noticed that after a few days it will go back to normal, but tonight I was playing RFM and it was fine then it changed to blurry pixelated again and stayed like that..
I am wondering if the motherboard or the cga plug may be faulty???
Any Ideas guys?


Very noticeable in the high score and hi score names

[Dazzat]

another pixelation

If you have a RFM you will know the colour is off

See the green blurring across the screen

[Dazzat]

another

[Marty Machine]

This looks more like a video-termination problem.

Old glass monitors (video or computer) have 75ohm termination resistors on the video input, or 1 each on the R,G & B signals etc...

In many cases, certain brands of modern LCD's don't have the termination resistors fitted (or different values).

The smeary effect is typical on a non-terminated signal, and will vary on various levels of brightness on your screen, hence the fault "coming and going".
It will show more on the hi-score and feature displays as they're the brightest parts of the display screen, and probably being fed with a full 2volts of video signal instead of 1volt required by todays LCD monitors.

Perhaps a few searches on google about video temination and/or RFM 'smearing' problems will come up with a mod, but it's basically just fitting 75ohm resistors onto the R,G B signals of the video cabling....
The resistors ensure that a 2volt signal (the old crt signal) appearing on the video/vga inputs is reduced to 1volt standard.

hope it helps.....

[Dazzat]

Thankyou for the reply Marty Machine,
Very interesting indeed.

I thought this is what helped that problem including down converting to 15hz when I installed this grey dongle with the GBS-8220 Video Converter

[casperthefriendly]

My RFM used to do the same thing from time to time - green bleeding across the screen. Mine would do it from time to time, then got a bit worse, but still intermittent.

I managed to trace the fault back to a bad connection on one of the two connectors goinginto the PC - try reseating things at that end and see how you go.

IIRC the connector that was causing my fault wasn't actually the one that feeds the monitor, but the larger one that does everything else.

HTH

[Dazzat]

My RFM used to do the same thing from time to time - green bleeding across the screen. Mine would do it from time to time, then got a bit worse, but still intermittent.

I managed to trace the fault back to a bad connection on one of the two connectors goinginto the PC - try reseating things at that end and see how you go.

IIRC the connector that was causing my fault wasn't actually the one that feeds the monitor, but the larger one that does everything else.

HTH

Definitely will check that one just in case, And use some CO cleaner that I uses for electricals at work to clean ports and wires

I'd really like to know where to buy new ribbon cables and new cga port for the rfm pc, I've looked in jaycar but no go... old technology is getting scarce

[Marty Machine]

1)
Looks like there's 3 controls (R,G,B levels) to adjust for video levels near the CGA-in socket (3 yellow trimpots).

I'm sure if you turn the one marked 'Green' or 'G' while the fault is present, you should see the smearing change as you adjust the trimpot.
I assume there's some kind of setup procedure that comes with the card?

2)
Assuming the above is setup correctly, it still doesn't guarantee what level of signal is coming out the VGA-out connector, whether it's 1volt or 2volt signals, the modern (non glass/crt) monitors will hate 2volt signals.


I'm sure there's gotta be some forums somewhere that support that CGA-to-VGA card, and associated setups/problems etc etc, or the manufacturers site themselves??

[humpalot]

This should help

or download the manual from http://www.jammaboards.com/store/cga-ega-yuv-to-vga-arcade-hd-converter-pcb-gbs-8220-gbs-8220.html

[Dazzat]

Yes I have been having a good look around the web and a lot of people have been talking about it on arcade machines but nothing on the RFM.
I understand the concept but can't find any instructions on how to do it with the resistors  so far.
I tried the trim pots but to no avail so far

[humpalot]

Have you played around with the clamp st and clamp sp settings in the menu of the convertor board?  Unless you get these settings perfect for your monitor then the picture is always going to look crap.

[Dazzat]

Have you played around with the clamp st and clamp sp settings in the menu of the convertor board?  Unless you get these settings perfect for your monitor then the picture is always going to look crap.

Tried this today and had no luck, not a difference at all unfortunately.. Still had the smear across the screen  BIG TIME, especially green

[Dazzat]

This looks more like a video-termination problem.

Old glass monitors (video or computer) have 75ohm termination resistors on the video input, or 1 each on the R,G & B signals etc...

In many cases, certain brands of modern LCD's don't have the termination resistors fitted (or different values).

The smeary effect is typical on a non-terminated signal, and will vary on various levels of brightness on your screen, hence the fault "coming and going".
It will show more on the hi-score and feature displays as they're the brightest parts of the display screen, and probably being fed with a full 2volts of video signal instead of 1volt required by todays LCD monitors.

Perhaps a few searches on google about video temination and/or RFM 'smearing' problems will come up with a mod, but it's basically just fitting 75ohm resistors onto the R,G B signals of the video cabling....
The resistors ensure that a 2volt signal (the old crt signal) appearing on the video/vga inputs is reduced to 1volt standard.

hope it helps.....

Is this what you would be talking about Marty Machine? This is about all I could find that remotely helps or could remedy what you are talking about

If your PC does not sense your monitor it is likely your monitor is not loading the RGB signals. Measure input resistance from one video signal (R, G or B) to ground with an ohmmeter, in 200 ohm scale it should read around 75 ohm. Some monitors have a switch or jumper to enable loading of video signals, if yours does not have this setting you can add three 75 ohm resistors from each video signal to ground as shown below.

[Marty Machine]

Is this what you would be talking about Marty Machine? This is about all I could find that remotely helps or could remedy what you are talking about

If your PC does not sense your monitor it is likely your monitor is not loading the RGB signals. Measure input resistance from one video signal (R, G or B) to ground with an ohmmeter, in 200 ohm scale it should read around 75 ohm. Some monitors have a switch or jumper to enable loading of video signals, if yours does not have this setting you can add three 75 ohm resistors from each video signal to ground as shown below.

Yep, the diagram you provided is exactly what i meant.

[Dazzat]

Is this what you would be talking about Marty Machine? This is about all I could find that remotely helps or could remedy what you are talking about

If your PC does not sense your monitor it is likely your monitor is not loading the RGB signals. Measure input resistance from one video signal (R, G or B) to ground with an ohmmeter, in 200 ohm scale it should read around 75 ohm. Some monitors have a switch or jumper to enable loading of video signals, if yours does not have this setting you can add three 75 ohm resistors from each video signal to ground as shown below.

Yep, the diagram you provided is exactly what i meant.

Thanks Marty Machine, I guess I just splice into the vga cable with the resistors and earth them, fingers crossed this works  Trip down to jaycar tomorrow