VGA to TV converter Used with X68000 / FM-Towns.

[Maxwar]

Ok I have this gadget here:



Did anyone try it with Japanese computers?

This is a cheap adapter you can buy for about 10$ shipped on ebay. Our Chinese friends have a unlimited supply of them.
I originally bought it to use my DOS retro PC on my TV and it works VERY well, it is awesome seriously, its even better than having a video card with a Svideo output as you have a built in menu to adjust the image size position and color as you like,  there's even a Pal/NTSC switch. I fell in love with it the moment i started using it.

Now i have recently bought a X68000 and a FM towns.  Both works fine with a VGA CRT monitor. I am using the same basic DB15-VGA adapter cable for both.
I would like to try using the VGA to TV adapter with my Japanese computers.

BUT!

I am worried about the mysterious issue where your X68000/FM-towns RGB output gets killed when used on some modern LCD or as ive seen in http://nfggames.com/forum2/index.php?topic=4901.0, by a RGB - VGA converted PCB.

Is there any kind of test i can do to make sure i wont fry my computers with this thing? It would be awesome if it just worked.
I even have some hopes that somehow maybe it would work with 15khz input too, which would be beyond awesome.

I have not seen any technical data or even theories about why the RGB out of those computers gets fried when connected to some device that it should have been able to work with. Its all very mysterious.

Advice is welcome.

[Endymion]

Somebody posted about this a couple years back on shmups.com and I'm still sceptical. I would have to think the cable were wired wrong somehow in order for this to happen. Unless of course it were due to just old hardware burning out, I mean come on that happens sometimes too. At any rate I made my own VGA converter cable from the one that came with my X68000 and haven't had any problems with all kinds of displays I've used it with through the years. Perhaps that is the secret.

[Maxwar]

Skepticism is good but there still might be something going on. There are at least 2 different people reporting this on the Shmups forum and a possible third person has a video about it on youtube.  Then there is this guy,Thoria,  on this vey forum who fried his output  using a GBS 8220 converter board.
See my first post for link

Maybe  all these people had a misswired adapters but in the absence of a definitive explanation this is all speculation.

Now i had posted on the Shmups thread and a guy responded that it could be caused by improper house wiring or some other things and it made me think a bit. Here's the commentary and my answer.

channelmaniac wrote:
The 74xx05 can only deal with so much current before it fries. The datasheets for the chips will show you what it can take.

Check the pins the signals are going to for grounding or for voltage feeding back into it.

Also, if you're on standard 110v in the USA check the outlets for proper wiring. If you have wiring that is reversed then you could be putting some NASTY voltages across a ground connection.

Home Depot sells a simple 3 prong outlet tester. Buy one and use it religiously.

Evilmaxwar wrote:
Even with the outlets and wiring done properly, I have also been wondering if this issue might not be related to the fact that X68k and FM-towns only have 2 prong plugs.
Maybe a ground voltage discrepancy between the two devices could result into said currents flowing through the wrong place.
Mind that im not an electrical expert in anyway but i sort of think there might be something there.

I just checked my "cheap" X68000-VGA adapter and the "shields" of the connectors are not even connected. This means that if there is a voltage difference between the chassis of the LCD and the Computer, there could be rogue current going through the chip.

There is actually a "ground" screw on both my FM towns and my X68k and im thinking that Simply connecting this to the Ground pin of your outlet or to the chassis of the LCD could be the proper safety measure against the kind of Failure described in this thread. I could also be totally off the track.
*Expert opinion would be appreciated here*

[Maxwar]

Well, lo and behold, i just tried it with my Fm-towns and it works perfectly for 31 khz.

It also appears to work with lower sync frequencies, i can see the FM-towns intro on my TV and if i load Shadow of the beast ( A game that wont work on a VGA monitor) I get the intro of the game and all the cut scenes. The image kinds of flicker and has some light distortion but if i play with the flicker and sharpness settings of the adapter it gets all right!!!

Where it did not work as well is with the gameplay itself.  It flickers horribly and the display is kind of mirrored in a split screen fashion. You can actually play the game but its not nice.
  Ill do more testing,  looks like this thing is not only a great VGA - TV adapter but could also be a poor man's (10$)  solution to the lack of multisync display!