> As I said, almost nothing in a computer uses -12V. It was
> originally needed by DRAM chips for bias, but DRAM has not
> worked this was for a decade. Now, the only thing commonly
> tied to -12V is an RS-232 port that would probably work as well
> in practice without it.
DMJ> You are right.. almost nothing.. Just the hard disk and
DMJ> CDROM drives. Some hard drive take 2.7 amps starting and
DMJ> about .7 running.
Actually, neither hard, floppy, nor CD-ROM drives ever use -12V: they are not
even connected to it! I think you overlooked a minue sign.
The four-pin connector that supplies power to drives of all kinds is very well
standardized with +12V, +5V, and two ground pins.
DMJ> Unless you just want to play, I still think you would be
DMJ> further ahead to buy a complete UPS surplus rather than this
DMJ> approach. It is to easy to under estimate the amount of time
DMJ> you will have to invest in something like this. If for some
DMJ> reasion the PC has to be replaced you have to hack up another
DMJ> one so it will work(you hope) with this approach.
DMJ> I still think your time would be better spent else where.
I'm not disputing this, but anyone in ham radio who wants to build something
these days has my complete support.
DMJ> BTW I was wrong when I said a friend of mine bought two APC 280
DMJ> UPSs for $30. As it turns out he bought two of the 500 watt
DMJ> units for $35. He said both units worked fine after he replaced
DMJ> the batterys. 500 watts is kind of overkill for this problem
DMJ> but the price is write.
It is precisely the batteries which are the expensive part.
-- Mike