It's worse than that, he's dead, Jim.. - Torch Triple X Part 3

Before anyone panics, the Torch isn't dead (I think). Rather, my ATX power supply is. While I was probing around the board, looking at signals, I noticed that the cyan display had actually turned magenta. This was different so I switched off the ATX supply, waited 20 seconds or so then switched it back on. 

And I got nothing.

After a little panic I realised that the green LED on the ATX supply hadn't lit up meaning that the supply was off. The red LED was lit though, indicating that it was in standby. Hmmm. I initially thought I'd popped a thermal fuse so I left it overnight and tried the next day.

Red standby LED is still lit
(centre bottom at the end of the black box)

Still dead.

So I tried checking the internal fuse and that was OK too.

Bugger.

Now I am in the situation where I'm not sure if the power supply died of old age, or whether a fault was on the Torch board that killed it. And, if there was, has that fault damaged the Torch mainboard? I know it was drawing a lot of current but the ATX supply could provide a crazy amount i.e. 25 amps at 5v and 16 amps at 12v. I could try and drive the board from my bench supply but then I can only provide the 5v. I may have to bite the bullet and buy another ATX power supply. I did have a spare but it went into the Amiga A2000. 

Unlimited Power! (Well up to 280W..)

To keep myself amused and useful I decided I should look at the schematics of the Torch and try to re-create them in KiCAD. 

I have used several CAD packages in the past but KiCAD is specifically aimed at preparing electronic PCB layouts and schematics. The learning curve is not too hard if you're only copying a schematic - and when I say copying I mean "make it look like the picture, I don't care if I've had to modify a 68000 block diagram to make the MMU..." so there's no chance of using my output to generate a new gerber file for the motherboard or anything daft like that.

The main reason I'm actually quite keen to get the schematics done is that the originals that I have are not really originals. They're photocopies of hand-drawn (possibly) originals and so the quality in some places has really gone down and there are several areas, notably at the very top or bottom of the drawings, where some information has been lost. This isn't as drastic as it sounds as it can pretty much be derived by looking at the context of the lines that seem to stop suddenly at the top (or bottom) of the page.

Anyway, here's an example which shows the 'Bus Masters' and is probably one of the most complicated of the drawings to generate.

Bus Masters. This is one of the most complicated ones.

While I work my way through the schematics and try not to lose my sanity, I will start searching eBay for an ATX power supply that also has -5V. 

“If it were easy, everybody would do it. Hard is what makes it great.”