Mac68k Forums

Hehe, well glad to see you're still around! I tried both the keyboard and the rear switch, and both methods didn't work. Now that I've traced out the whole startup circuit, I'm pretty confident mine will work after I use known-good new batteries though. There were definitely broken traces though, so I still needed to repair it even if my batteries were half of the problem.

I originally thought the top half of Gamba's startup circuit was for the ADB power button and the bottom half was for the rear power button, but I was wrong. Actually, most of the startup portion of the circuit is shared by both the keyboard and the rear power button. The top part of the circuit is for power on, and the bottom part of the circuit is for power off. UB11 (VIA2) pin 13 is the /POWEROFF signal that tells the power supply to shut off. The power off circuit is also hooked up to the second pole of the power button in order to enable pushing the power button to shut off the system.

If your rear power button doesn't work but your keyboard power button does, there are only a few connections that could be causing that problem. I would verify the connections on R9 and C3 (and their connection to the power button). It could also be the connection from R3 to the power button. Everything past R3 is shared by both the keyboard and the rear button.

I didn't notice a typo on Gamba's schematic, but he did note that the components are for the II -- the IIx may be different. My IIx seems to have different component numbering from most, so mine actually matched Gamba's diagram.

Good news: My IIx now chimes and shows video when it's jump-started! I found another broken connection, and it's a pretty important one -- the main clock. The broken connection, at least on my IIx, was between UG8 pin 9 and R22. UG8 is right by a capacitor, so the leaking capacitor had eaten up the trace between that pad and a nearby via. I ran a tiny temporary wire between the pin and the via to repair the trace, and now the IIx is alive. (P.S. Thanks to bbraun for sending me a NuBus video card to use!) I plan on completely removing that chip and cleaning underneath it, but for now it's working!

Well, I got the new batteries today and there's still something wrong with my power on circuit. Now what I'm seeing is that with the batteries in, the system immediately powers itself on and the power button won't shut it off.

I think something is screwed up and allowing the battery voltage to get to places it shouldn't get to, or something like that...

Oh nice you found the issue. Did you take before/after pics of the patch wire? I am looking forward to your explanation since I don't really understand the circuit. It seems complicated for what it does.

Here's my explanation of the circuit. It ended up being a lot more difficult to write about than I was originally thinking. I think an animation or more pictures would help, but it's a start. It's so difficult to put into easy-to-understand words!

Thanks! That's for sure. I was going to say that it probably helped using a power supply that actually has a +5V standby voltage, but then I remembered the IIcx/IIci have a +5V standby voltage and they still use all the complex NAND gate stuff!

Thanks tt!

I just got your battery holder board installed on the IIx. Looks great! It was truly impossible to remove the solder from the ground pin on the IIx...I ended up having to heat up the existing solder and push the holder board's pin through.

That issue is due to the ground plane pulling the heat away.

You have to use a heatgun on low heat while soldering, or desoldering.