Strange crashes..

[Karlos]

It turned out to be the very old PSU for some reason wasn't supplying enough current on the -12V supply. Since installing the new PSU about 4 years ago I've never seen this problem occur again...

Strange that this caused crashes. I once forgot to wire in the -12V rail entirely and the worst I got was half-wave rectified audio (not pleasant) and failure of the serial port to operate (again, signal rectification). As soon as I realised my mistake and connected it, all was well.

I don't know how your machine is wired up, but I used both the original rear port connector as well as the motherboard floppy power header as places to inject the 0, 5 and 12V rails. The -12V rail is only attached via the rear connector, but then again, current requirement is minimal. I did find that even after supplying the HD, floppy and CD directly from the PSU, the combined draw of the 1200 motherboard, BlizzardPPC and BVisionPPC was a bit more than I was comfortable feeding in through the original power connector, which is why I decided to inject additional power via the motherboard floppy power header.

[Karlos]

Sounds like it could be time to break out the alcohol to clean up all your connector contacts.

Won't that be a bit fiddly after a skinful? :drink: :drink:

[Karlos]

That PSU if I recall correctly had a max of 500ma on the -12V supply. So then I bought a new PSU that had -12V @ 1000ma (again if i recall correctly, suffice to say the only difference was a higher rating on the -12V) and have never seen the problem since...

That's why I put it down to being something to do with the -12V, but I can't be 100% certain as I was just so happy the problem was solved I never checked it out any further...

Holy crap, 1A for -12VDC? What's the overall wattage of that thing? Even my CoolerMaster 850W PSU only puts out a maximum of 800mA for -12VDC.

I guess your newer PSU may have cleaner output or something. Certainly there's nothing in the A1200 that draws on the -12V aside from audio and serial etc. Not exactly what you'd call heavy-duty requirements.

[Karlos]

Wow, I've never seen such low wattage PSUs with such high -12V ratings. Modern PC PSU's only have such high-rated +12V rails because you can step it down to whatever low-voltage/high-current requirements are needed directly on the device.

I thought 800mA was Overkill 9000 (TM) :lol: I wonder what uses -12V at anything like that current rating?

[Karlos]

That's true, I don't think I've ever seen any Amiga peripheral that required more that 100mA @12V... kinda makes me wonder why go up to 800 let alone 1000...

Hard disks and 12V fans are capable of pulling a bit, but they use the +12V rail, of which there's usually plenty of amps available. But -12V ? *shrug*

[Karlos]

@Franko

Did it not occur to you to check a different PSU before embarking on replacing the edge connector?