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| IICX Restore - Graphics issue |
Posted by: smrieck511 on 2026-06-06 21:59:31
If it is outputting pure white, either
1) the IIcx boot process is not proceeding far enough to give you a mouse cursor and disk request icon,or
2) I would think that an input to the video card DAC is stuck high. That BT chip is the DAC. It should be getting data from the VRAM chips, but it probably passes through some 74 family logic on the way. I would find those 74 series chips and replace/ttest them.
for #1 have you tried having a bootable floppy in the drive at boot time? I have not tried to boot floppy but I will tomorrow. I'm so used to working on SE's and SE/30's that it didn't occur to me that these might behave differently without a startup disk. if that's not it, I will definitely look into the 74 series logic chips. |
Posted by: trag on 2026-06-06 22:05:36
I have not tried to boot floppy but I will tomorrow. I'm so used to working on SE's and SE/30's that it didn't occur to me that these might behave differently without a startup disk. if that's not it, I will definitely look into the 74 series logic chips.
I think there are sometimes Muxes 74xx151, 153, or 157, most likely, that take data from the VRAM chips and route it in the appropriate number of color/grayscale bits to the DAC. The logic on the video card controls the Muxes so that the right data from teh right VRAM chip(s) are used in the muxed signal.
However, another possibility is that that video card is an old one not intended for a VGA/Macintosh monitor. In the really old days there were some video cards meant to connect to their associated monitor only. But that would be a fairly rare case, I think. |
Posted by: smrieck511 on 2026-06-06 22:45:19
tried a boot floppy and it definitely stays in the drive and makes all the correct sounds like it's loading the operating system. However, still white screen on the monitor. |
Posted by: smrieck511 on 2026-06-07 11:34:30
this card is the "BCGM0322 high resolution display video card". Everything I've read indicates it is compatible with the Apple M1212 monitor. I know that the monitor is functioning correctly because the guy I bought it from demonstrated it for me a few days ago and it was fine.
again, the boot floppy makes all the telltale sounds of a loading operating system but of course just white on the monitor screen. |
Posted by: Durosity on 2026-06-07 12:59:27
this card is the "BCGM0322 high resolution display video card". Everything I've read indicates it is compatible with the Apple M1212 monitor. It is. Basically everything of this era is compatible with that monitor.
I know that the monitor is functioning correctly because the guy I bought it from demonstrated it for me a few days ago and it was fine. Good so that rules that out.
again, the boot floppy makes all the telltale sounds of a loading operating system but of course just white on the monitor screen. So again that suggests the Iicx is at least partially working.
Realistically we're either looking at an issue with the BCGM0322, or a NuBus issue with the Iicx. Since the display does show an image, my money is on the card itself. |
Posted by: smrieck511 on 2026-06-07 15:24:02
It is. Basically everything of this era is compatible with that monitor.
Good so that rules that out.
So again that suggests the Iicx is at least partially working.
Realistically we're either looking at an issue with the BCGM0322, or a NuBus issue with the Iicx. Since the display does show an image, my money is on the card itself. thanks so much for your help. I guess the next step would be to put the scope on various parts of the card but I'm just lost as far as what to look for.
I did order another video card. Just couldn't help myself 50 bucks on eBay so that will definitely narrow things down. hopefully that card will just work but I'm still gonna work on repairing this one. |
Posted by: Durosity on 2026-06-07 15:35:04
I guess the next step would be to put the scope on various parts of the card but I'm just lost as far as what to look for. This is where my knowledge becomes less valuable.. you’ll likely find others car help more in this area. I mean I can often find faults.. but it just takes lots of faffing around 🤣
I did order another video card Good. It’s handy to have alternatives to test things with. It’s incredibly difficult to fix something if you can’t even narrow down where the fault is. Did you get the same kind of card again? If so you could potentially swap parts between them, although there is the risk of something frying a component that was previously working correctly. |
Posted by: smrieck511 on 2026-06-07 18:37:33
this one's totally different but I'm just looking for a good 640x480 256 colors and I'm happy. |
Posted by: Durosity on 2026-06-07 22:03:54
Oh, looks like it’s had the optional vram upgrade too! |
Posted by: smrieck511 on 2026-06-08 09:27:22
Oh, looks like it’s had the optional vram upgrade too! Exactly. All I want is 256 colors 640x480...is that too much for a man to ask in the 21st century? |
Posted by: croissantking on 2026-06-08 09:33:23
Exactly. All I want is 256 colors 640x480...is that too much for a man to ask in the 21st century? Ugh the Toby card. No separate sync output. No problem for your M1212 but annoying for many newer monitors. |
Posted by: smrieck511 on 2026-06-08 10:38:11
Ugh the Toby card. No separate sync output. No problem for your M1212 but annoying for many newer monitors. Right. I guess the issue is the refresh rate being 67mhz or above for some LCD's? |
Posted by: croissantking on 2026-06-08 10:54:47
Right. I guess the issue is the refresh rate being 67mhz or above for some LCD's? It’s different to that. Analogue video cards put out horizontal and vertical sync signals. Older cards such as this one combine those signals on one pin but newer screens often expect to see those signals on two separate pins. It’s not just LCDs, some CRTs don’t work with composite sync either. |
Posted by: smrieck511 on 2026-06-08 13:42:51
got it...I don't suppose there's a schematic for the BCGM0322 anywhere? |
Posted by: smrieck511 on 2026-06-13 09:36:22
got the new card. Everything is working 100% now. So in my spare time I'll work on the other card. Thanks again. |
Posted by: Durosity on 2026-06-13 10:31:41
Awesomeness! |
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