IICX Restore - Graphics issue

[smrieck511]

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.

 

[trag]

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.

 

[smrieck511]

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.