Non-obvious compatibility of M1297 monitor

Question

I bought an Apple IIgs recently. I didn't do my research well enough and wound up with an M1297 monitor, which of course appears to only be compatible with Macintosh IIs and such, rather than the A2M6014 I needed.

I could simply resell it as it works perfectly AFAICT, but that's a shipping hassle I'd rather avoid if possible.

Are there any 8 or 16-bit systems that could work with this monitor? Adapters and cables are fine if necessary even if they degrade the signal.

My research so far; if any of this is incorrect please let me know:

• C64 / Atari 8-bit: not a chance

• Atari ST: this appears like it might be vaguely possible for lower resolutions (same refresh rate horizontally if I'm reading things right) though the monitor port on the ST has a bizarre pin arrangement

• Amiga: again, maybe, due to refresh rate

• Sharp X68000: don't know much about this one

Obviously I could just get a Macintosh II or equivalent but I'd rather get a couple of the machines before that, if ever. I assume I'm correct on the C64 being completely incompatible even with a potential adapter, which is a shame as I have a C64 sitting around with no monitor.

Answer 1

While the IIgs video and Mac video both decent from the Apple III video (connector) and even look superficial the same, the most important difference is how sync signals are handled. Where the Mac handles each sync signal seperate, the IIgs interface imposed sync on the colour signals.

Pin IIgs signal                          Mac Signal
  1 Signal ground (Red)                  Signal ground (Red)
  2 Analog RED with sync                 Analog RED
  3 Composite sync                       CSYNC
  4 No connection                        Monitor sense 0
  5 Analog GREEN with sync               Analog GREEN
  6 Signal ground (Green)                Signal ground (Green)
  7 -5 volts DC                          Monitor sense 1
  8 +12 volts DC                         No connection
  9 Analog BLUE with sync                Analog BLUE
 10 No connection                        Monitor sense 2
 11 Sound                                Signal ground (CSYNC/VSYNC)
 12 NTSC/composite color out             VSYNC
 13 Signal ground (Blue)                 Signal ground (Blue) 
 14 No connection                        HSYNC ground
 15 No connection                        HSYNC

Are there any 8 or 16-bit systems that could work with this monitor? Adapters and cables are fine if necessary even if they degrade the signal.

Then many are possible in theory. In reality it's not just signal adaption, but as well frame design. Looking at the monitor's specs may help to decide.

The most simple would be a VGA adaptor, which just needs to swap some lines. Of course you would need to only used modes fitting the frame timing. There are many descriptions out there, so pick your favorite :))

C64 / Atari 8-bit: not a chance

Sure it's possible, but beside signal line twisting, some additional components might be needed.

Atari ST: this appears like it might be vaguely possible for lower resolutions (same refresh rate horizontally if I'm reading things right) though the monitor port on the ST has a bizarre pin arrangement

Again, just a pinout swap needed - much like ith VGA.

Amiga: again, maybe, due to refresh rate

Same as Atari.

Sharp X68000: don't know much about this one

Before thinking here, get one first .. they are somewhat rare outside Japan :)

Obviously I could just get a Macintosh II or equivalent

Obviously you should. Best would be a Mac LC475 (family member) as not only the screen fits, but it's as well the best option for classic 68h Macs. But best of all, you could plug in a IIe card and have both worlds in one machine.

I assume I'm correct on the C64 being completely incompatible even with a potential adapter, which is a shame as I have a C64 sitting around with no monitor.

As said before, it would work, but only as B&W and with additional effort beyond a simple cable. Considering you seam to want a compact setup, I wouldn't do it, but rather look for one of these cheap Chinese converters able to input S-Video (C64, Atari 800), composite (TI 99/4A) or VGA and output VGA which in turn can be applied to this screen - or a new HDMI based. They are the most versatile solution for old/home computer video.

Answer 2

While the M1297 is an excellent quality Trinitron CRT, it will be quite difficult to use it with anything other than the various color Macintosh systems for which it was designed.

The main issue is that it's the wrong input format for the 8-bit systems you mention (RGB vs. composite or S-video), and its the wrong horizontal sync frequency for the 16-bit systems you mention (not 15.7 kHz capable). Not to mention dealing with the 15-pin DSub connector, only common on Apple color Macs and (in modified form) IIgs.

If you want a quality Trinitron CRT that supports those systems, you should look at the Sony PVM series. They normally have inputs for RGB, CGA, S-Video, and Composite and they are designed for the 15.7 kHz horizontal frequency used by all those systems.

I have a Sony PVM-1342 which I have used as a CRT with:

• Apple IIgs (RGB)
• Apple II/Plus/IIe/IIc (Composite)
• C64 (S-Video)
• C128 (40 column S-Video and 80 column RGBI)
• Atari 800 (S-video)
• Amiga (RGB)
• BBC Micro (RGB)
• Sega Genesis (RGB)
• PC clones with CGA/Tandy (RGBI)

All the above are a simple matter of the correct cable for me, except for the Apple IIgs. For RGB output, I usually go from native port to SCART, then from SCART to BNC connectors on the PVM. So, it is actually two cables where the first is system-specific and the second is common.

On the IIgs, I install a jumper on the bottom of the motherboard to move the Composite Sync signal to the pin that is expected by the common 15-pin DSub to HD15 (e.g. VGA style) dongles used on Macs. Then, I use my normal HD15 to BNC cable to go from the dongle to the BNC connectors on the Sony PVM.

Nothing I've found beats a Trinitron CRT for any of these retro systems, if you want an authentic CRT display, vice using scan converters and LCD displays.