Mac IIci no video from motherboard, but I do get it from video card.

[DistantStar001]

Not really a huge deal, but it would be nice if I could get this fully functional.

Just as the title says, I got a Mac IIci that came with a NuBus video card and an Apple branded IIci Catche Card. It needed a full recap, and the battery was dead (since removed). Other than that, it was just really filthy inside.

Using a VGA adaptor (which works with my Mac IIfx, LC III, and PowerBooks, and when attached to the motherboard, I get a happy Mac chime, but no video on the screen. When connected to the NuBus Card everything works. At first, I thought that it was some sort of jumper. Something on the motherboard that was selecting for the NuBus instead of the internal video. But no such jumper exists.

Side Note: I removed the NuBus Card when testing the motherboard connection. Not sure if it was necessary, but it seemed like a good idea.

Another thing, it's booting without a battery. I didn't think it would, but it does. Doesn't remember its settings, but it boots.

That's it. Just this one issue that would be nice to fix, if anyone knows how. Beyond that, it seems to be fully functional. Any ideas?

 

[Byrd]

It's possibly the adapter, the onboard video of IIci requires a monitor or adapter that works with "sync on green and perhaps your monitor isn't being properly detected. Good it works off the nubus video card though, can you see the icon for the onboard video in the Monitors control panel?

 

[bigmessowires]

Agree with @Byrd, your monitor probably doesn't support composite sync or sync-on-green, which is what the IIci built-in video puts out.

 

[finkmac]

As people mentioned, the internal video is very picky.

Make sure you're using one of them video adapters with 2 rows of dip switches, and a monitor that does SoG like a NEC multisync...

There's another potential stumbling point though, the IIci internal video requires memory in bank A... But the IIci will happily boot with no memory in that bank.




See here, bank A is the side by the SCSI port.
When I recapped my IIci and tested it, I didn't get video from the internal port. Bashed my head at the wall for several hours before questioning where Bank A was... Yeah, I had installed the SIMMs in bank B...

 

[DistantStar001]

Okay. So if I'm understanding this correctly, I have a fully functional Iici, but I either need a different VGA adaptor, or different monitor to test the motherboard video. The thing is, the monitor usually tells me if there is an incompatible signal. It was doing that with the NuBus card before I found the correct setting. When connected to the motherboard, the monitor doesn't register any signal at all. However, it did see that something was attached (screen goes into sleep mode when attached to an inactive device).

Make sure you're using one of them video adapters with 2 rows of dip switches, and a monitor that does SoG like a NEC multisync...

The adaptor has two rows of dip switches, but I'm not sure about the other.

 

[jmacz]

The IIci does not need a battery to boot. It gets some 5V power from the power supply to drive the startup circuit.

Which monitor are you using? I have seen the behavior where a monitor won’t go into sleep mode because it sees something and stays on a black screen due to the vga adapter settings (dip switches). The IIci onboard video is less forgiving than the LCIII or other newer 68ks with onboard video.

You could also use a multimeter to check each pin on the db15 port on the motherboard. There are pin outs available online. You could check to make sure you are seeing something on red, green, blue, hsync, and vsync.

 

[bigmessowires]

If your monitor doesn't support composite sync or sync-on-green, then it doesn't matter which VGA adapter you use - unfortunately it's not going to work. You would need to try a different monitor. I've been working on a design for a VGA adapter with an integrated sync splitter, which might eventually bridge this compatibility gap.

I'm just guessing, but the monitor probably shows an "incompatible signal" error if the horizontal or vertical refresh rates are outside the supported range. But if there is no sync signal at all (from the monitor's viewpoint, since it doesn't see the composite or sync-on-green) then it would act like there's no signal.

If you have a logic analzyer or oscilloscope, and you're willing to poke some test wires into your IIci built-in video port, you could confirm that it's working. If you connect pin 4 to pin 11, that will make the IIci think that a 640x480 monitor is attached and it will start sending a video signal. Using pin 11 as a ground reference, you can examine the composite sync signal on pin 3, and the R G B signals on pins 2, 5, and 9. Composite sync should be a digital signal that's either 0V or 5V, and the R G B signals will be analog in the range 0V to 0.7V I think.