https://nfggames.com/forum2/index.php?topic=6657.0

Has somebody who made an adapter, listing the pinout.

Dominus wrote on 2025-06-07, 16:56:

So I have an old FM Towns tower that I finally wanted to get going but ran into the problem that I have no cable to connect it to a monitor.
The FM Towns has a 15-pin female connector that says "Analog RGB". It's wider than VGA and a Mac DB15 (or is it DA15?) fits.

What kind of adapter to VGA can I use?

The pinout is easily found on the net. Or if you prefer more solid info, the 3FmTowns.pdf is the #1 source of that.
But the pinout is only half of the problem. Towns uses 15kHz (low), 24kHz (medium) and 31kHz (high resolution) modes. And the default is 24k, though most games will boot into 31k. Not all though and some are mixed mode - like EOB2 intro running in 24k but the game itself in 31k.

Newer Towns will up-convert 24k to 31k, and starting with EA series (Fresh-E and later) also the 15k modes. And these machines have a standard VGA connector. Anything older, esp. the grey towers, will require a tri-sync monitor or a converter. I use OSSC and I've made my own high quality DB15 cables. You really want a proper 75ohm coax for the RGB lines if you intend to use a modern hi-res LCD TV or monitor with upscaler/converter like OSSC.

Do not use the adapter in the first pic. You will fry the output!

There are 3 generations of Towns video output.

"Old" = RGBS (unique pinout)
"New" = RGBHV (PC98/X68000 pinout)
"Modern" = Standard VGA

A lot of online pin out diagrams combine Old and New, but this is wrong, they are separate generations on most machines.

And as stated, the Bios on old Towns is 24khz, most games run in 31khz, but some popular titles such as Turbo Outrun are 15khz.

SuperDeadite wrote on 2025-06-11, 00:54:

There are 3 generations of Towns video output. […]
Show full quote

There are 3 generations of Towns video output.

"Old" = RGBS (unique pinout)
"New" = RGBHV (PC98/X68000 pinout)
"Modern" = Standard VGA

Which generation does not support RGBHV output? If anything I would expect the combined sync to be missing on the newer models - but I'm not saying it is missing, I've never checked. And the pinout should be identical for all the machines that do not have a standard VGA connector, see attached picture.

One thing that can be missing is the SCLK, which is pixel clock. Pity as it could be useful for perfect pixel scaling but OSSC does a great job upscaling the signal either way.

Deunan wrote on 2025-06-11, 10:20:

SuperDeadite wrote on 2025-06-11, 00:54:

There are 3 generations of Towns video output. […]
Show full quote

There are 3 generations of Towns video output.

"Old" = RGBS (unique pinout)
"New" = RGBHV (PC98/X68000 pinout)
"Modern" = Standard VGA

Which generation does not support RGBHV output? If anything I would expect the combined sync to be missing on the newer models - but I'm not saying it is missing, I've never checked. And the pinout should be identical for all the machines that do not have a standard VGA connector, see attached picture.

One thing that can be missing is the SCLK, which is pixel clock. Pity as it could be useful for perfect pixel scaling but OSSC does a great job upscaling the signal either way.

How's your Japanese? That is the typical "combined" pinout I mentioned. It states that pins 14 and 15 are model based options. Most "gray machines" only output RGBS. I have personally confirmed with my own eyes that pins 14 and 15 are not connected to anything on my UX20.

RGBHV came later, my base Fresh has it, but I believe the HR models did first.

Where it gets very confusing is with the various video cards. I added one to my Fresh to restore the missing 15khz output, and it actually outputs both.

Early Towns monitors only accept RGBS, but from what I've seen, all monitors that take HV will also take S.

It's a complete mess caused by Fujitsu's attempt to boost sales by adding compatibility with NEC monitors.

To the OP: Unscrew the 3 expansion slot covers, shine a light inside and look at the connectors. If all 3 are white and look the same, your Towns is RGBS. If you see one white slot and 2 black slots (the black slots will look thiner), your Towns is a later model and probably has HV sync.

SuperDeadite wrote on 2025-06-11, 11:40:

That is the typical "combined" pinout I mentioned. Most "gray machines" only output RGBS. I have personally confirmed with my own eyes that pins 14 and 15 are not connected to anything on my UX20.

Curious. Could be your UX20 is actually the exception rather than the norm, due to the built-in monitor? I'm pretty sure my grey towers (20F and 40H) both output RGBHV. That being said it was a good few years ago when I tested it with a scope, I could be misremembering things. I'll check again in near future to be sure, but I'm setting the OSSC for RGBHV, not RGBS. I didn't even connect pin 7 from FM Towns to anything on the VGA connector in my cables.

I also connected the monitor directly, and it does work if the sync is in range (so pretty much 31k mode only) but that particular LCD does have a limited support for C-sync and sync on green. So that experiment doesn't actually prove anything on its own.

Did you ever check if the monitor part of your UX20 is capable of working with external RGBHV? Or does it accept RGBS only?

SuperDeadite wrote on 2025-06-11, 11:40:

Where it gets very confusing is with the various video cards. I added one to my Fresh to restore the missing 15khz output, and it actually outputs both.

Eh, the video cards are a separate topic. I'd say unless someone wants the 15k ouput (and only that, as these are not guaranteed to work with any other signal) they should stick to the standard RGB output.
In other words it's of use to arcade fans, because these folks would be interested in the game ports running at 15k to use with their cabinets and/or arcade monitors. Everyone else would rather have 31k output for VGA or modern HDMI.

Deunan wrote on 2025-06-11, 12:57:

Curious. Could be your UX20 is actually the exception rather than the norm, due to the built-in monitor? I'm pretty sure my grey […]
Show full quote

SuperDeadite wrote on 2025-06-11, 11:40:

That is the typical "combined" pinout I mentioned. Most "gray machines" only output RGBS. I have personally confirmed with my own eyes that pins 14 and 15 are not connected to anything on my UX20.

Curious. Could be your UX20 is actually the exception rather than the norm, due to the built-in monitor? I'm pretty sure my grey towers (20F and 40H) both output RGBHV. That being said it was a good few years ago when I tested it with a scope, I could be misremembering things. I'll check again in near future to be sure, but I'm setting the OSSC for RGBHV, not RGBS. I didn't even connect pin 7 from FM Towns to anything on the VGA connector in my cables.

I also connected the monitor directly, and it does work if the sync is in range (so pretty much 31k mode only) but that particular LCD does have a limited support for C-sync and sync on green. So that experiment doesn't actually prove anything on its own.

Did you ever check if the monitor part of your UX20 is capable of working with external RGBHV? Or does it accept RGBS only?

SuperDeadite wrote on 2025-06-11, 11:40:

Where it gets very confusing is with the various video cards. I added one to my Fresh to restore the missing 15khz output, and it actually outputs both.

Eh, the video cards are a separate topic. I'd say unless someone wants the 15k ouput (and only that, as these are not guaranteed to work with any other signal) they should stick to the standard RGB output.
In other words it's of use to arcade fans, because these folks would be interested in the game ports running at 15k to use with their cabinets and/or arcade monitors. Everyone else would rather have 31k output for VGA or modern HDMI.

UX20 has both input and output. Both ports have nothing attached to pins 14 and 15. I know a few people that have soldered wires from 14 and 15 to 7 to get X68000s working on them.

Remember, there were gray tower machines built and sold as budget machines after the Fresh line was already out. They use different pcbs then the original grays.

As stated above, a quick and easy test is to look at the expansion ports. Newer Towns all have one white legacy port for old boards and two of the faster black ports for the new type.
Old Towns will have 3 white ports.

Video Cards are quite simple, they do not use drivers, you just plug and go. They do not scan convert, only output native. So 15/24/31 switching works automatically. There is no way to force a Towns to downscan everything to 15khz. The video boards also have an Svideo encoder, (custom port) but it only encodes 15khz signals. It does nothing when software selects 24/31.

SuperDeadite wrote on 2025-06-11, 13:28:

UX20 has both input and output. Both ports have nothing attached to pins 14 and 15. I know a few people that have soldered wires from 14 and 15 to 7 to get X68000s working on them.

Good to know. These machines are a bit too bulky for me (not to mention expensive to import), but this bit of info might come in handy. Still, OSSC way would work with a small wiring change in the cable. And/or monitor with support for composite sync - or a a small LCD TV with VGA input could perhaps do it.

SuperDeadite wrote on 2025-06-11, 13:28:

They do not scan convert, only output native. So 15/24/31 switching works automatically. There is no way to force a Towns to downscan everything to 15khz.

What I meant is quite a few arcade ports have the option to switch video mode to 15k, so if the only problem was your machine is up-converting everything (like the newer Fresh models) then the video card allows you to bypass that. My point was it doesn't really offer anything else that would not be already covered by the standard RGB output. So unless you actually need 15k output there is no need for extra video card.

Thanks for the ton of information 😉
Unfortunately I tried that adapter before these posts. Didn’t work and as has been said here I might have fried the port ;(
Ordered a correct one I hope.
And I can‘t look inside the device for another few days but will report back!

Deunan wrote on 2025-06-11, 14:02:

Good to know. These machines are a bit too bulky for me (not to mention expensive to import), but this bit of info might come in […]
Show full quote

SuperDeadite wrote on 2025-06-11, 13:28:

UX20 has both input and output. Both ports have nothing attached to pins 14 and 15. I know a few people that have soldered wires from 14 and 15 to 7 to get X68000s working on them.

Good to know. These machines are a bit too bulky for me (not to mention expensive to import), but this bit of info might come in handy. Still, OSSC way would work with a small wiring change in the cable. And/or monitor with support for composite sync - or a a small LCD TV with VGA input could perhaps do it.

SuperDeadite wrote on 2025-06-11, 13:28:

They do not scan convert, only output native. So 15/24/31 switching works automatically. There is no way to force a Towns to downscan everything to 15khz.

What I meant is quite a few arcade ports have the option to switch video mode to 15k, so if the only problem was your machine is up-converting everything (like the newer Fresh models) then the video card allows you to bypass that. My point was it doesn't really offer anything else that would not be already covered by the standard RGB output. So unless you actually need 15k output there is no need for extra video card.

As someone still using CRTs, the 15khz output is so much better than the Fresh's "upscan" mode. It doesn't really do anything to the graphics, just displays 15khz content in a small window with a big black border taking up the rest of the screen space. And when using a standard sized 15'' monitor, the reduced image size is really annoying 🤣.

If I had the money, I'd buy up tons of Towns machines just to document the insane revisions Fujitsu made, my original machine was a 2H. It had a socketed CPU, but used the old type of CD-ROM that didn't have a locking spindle, you put the CDs into the lid itself and it pushed them into place upon closure. The lid closed sensors died, but fixing them would have been insane, as all the ribbon cables on that machine were directly soldered to the PCB, no sockets at all. So I ended up trading it off to a friend for cheap.

Currently I have a Fresh with AMD 586x133mhz ODP board, UX20, and a Car Marty. I mostly use the Car Marty for really bitchy games like Shadow of the Beast 2 that refuse to boot on a system with more than 4mb RAM installed. Towns is quite the ride into the bizzare world of a company desperate to stay alive. It's a complete mess, but I love me some RayXanber!