The power supply burned out (puff of smoke!  Hole in chip!), and I haven't
had much luck working without it or with another.  I suspect something in the
unit itself shorted and overloaded the supply.

Away, free if you can come and get it off my porch in Ann Arbor.  Includes
a 170 Mb hard drive (last know to be loaded with SCO Unix).  Monochrome
screen, OK feeling keyboard.

16 responses total.

It's gone.

Can anyone tell me why the power supply cord has *four* conductors?

The battery is labeled "13 volts" (NOT 12 volts!), and I've managed to get
the machine working for short periods on a car's electrical system (directly
into the batetry contacts) and on the battery itself after giving it a shot
of juice from a car charger. But I think its working voltage levels are a bit
higher.

The power supply *is* hosed, apparently. When I tried it with a new fuse I
got a brilliant blue light show from the AC socket, even though the DC
resistance measured in the 700K range (putting the probe at the point just
after the fuse of course) after the attempt.

DC resistance != AC impedance @ 60Hz!

Somehow there's a charging supply and a running supply on those.  We've got
another with a similar power supply (which didn't work with the laptop either,
if that helps).

The power would probably be going through one of the big capacitors then.

That other power supply, it *does* work with some other machine? Wouldn't that
power supply be needed elsewhere? I suppose I could give it a try. You might
for now just plug it into the wall and measure the output voltages. And get
the rating (and actual voltages) of the other battery.

The charger I have now is labeled 110 volts OR 220 volts AC in, 50-60 Hz;
and 12 to 20 volts out DC. There is no switch for selecting 110/220.

Oh yes, the battery when I got it read something like 2 volts. I managed to
get it up around 13 volts, but couldn't put enough juice in it to last long
or run anything. As I said, my current theory is that it will work, but that
the system requires just a little more oooomph than a car electrical system
can muster. (14-15 volts actual versus 12-13 volts.)

If you send me email at scott@rt-systems.com I'll remember to measure voltages
on the other power supply.  It still works with its original laptop, but it
didn't work with the laptop you now have (although I never tried mixing them
until the power supply on the other one died).

It's very possible to get a bright flash when plugging in even a working
power supply.  There is a big capacitor, in most power supplies, that is
totally discharged before it's plugged in.  Upon being plugged it it will
draw a LOT of current for a fraction of a second as the capacitor comes up.

There are 4 contacts on the battery because two go right to the plus and
minus sides of the battery and the other two to to a temperature sensor
inside the battery pack.  Most batteries start dissipating the charge 
current as heat after getting fully charged.  The charging circuit looks
at battery pack temperature to determine if the pack is charged.

There are only two contacts on the battery. There are four in the cord
connecting the power supply to the computer.

Since 12 to 20 volts is a rather HUGE percentage change, is it possible
that it means 12 AND 20 volts, one set of conductors for each?

The other supply at work (which I don't for sure is the same thing, but the
connectors were the same) says "DC 18v", plus a "Charging 15-20v" or something
along those lines.

Maybe there's one feed for logic power, and one for charging, with an
automatic changeover to battery when the logic supply goes away?

Maybe drew could attempt to count the number of cells in the battery pack and
multiply the result by 1.2 to come up with the right voltage.

There appear to be ten C-cell-sized cells in the pack, for 12.0 volts. The
pack is labeled "13 volts" however. I'll try giving it another shot of juice;
it's back down to 2 volts.

Perhaps the logic supply is more tightly regulated than the charging
supply.

I have a charger/power supply board for a laptop.  It requires 12-30 VDC, if
I recall, as a single input.  The interesting thing is that this voltage
must *not* be grounded to the same point as the battery.  If you tie the two
negative wires together, bad things happen.

Still doesn't tell what to do about the second pair of conductors.

I have had the machine running just now.

Battery on car charger for a few hours on the "2 amp" setting put enough juice
in it to run for a short while. Long enough to boot up a DOS floppy several
times. The battery measured 13.9 volts.

It boots DOS floppies and runs fine.It does not boot from the hard drive,
though. Running FDISK results in "Error reading fixed disk". Partition Magic
loads, then stalls with a blank screen of a power-off-on reboot. Attempting
to boot Slackware floppies most of the time causes a power-off-on reboot
somewhere in the middle of the process, though I did manage to get as far as
logging in as root and running the Linux fdisk and typing 'p'. I got a few
lines of text - I *think* they were partition descriptions - and it power-off-
on rebooted before I got a chance to read it.

The red "BF/BL" light finally came on. I'm putting yet more juice in the
battery.

The electrical system on my station wagon can also power the laptop, provided
that the engine is running. The other car, having a not-quite-up-to-snuff
alternator, does not generate sufficient voltage.

There's another computer show coming up at GTC; and I've seen laptop hard
drives at these. However, I'd like to try out a known good hard drive sometime
before then, to be sure that the problem isn't somewhere in the IDE circuitry.

Maybe you should open it up and make sure I didn't put the disk back in wrong.

Where do you live?  I have a spare 120 meg laptop drive, but I'm in
Houghton.

Re #15:
    I live in Wyandotte, about 50 miles east of 'Arbor and close to the
Detroit River. It's a long ways from Houghton.

Re #14:
    You assembled the machine correctly. The cable has an idiot-proof
connector (pin missing from drive, plug in hole that the missing pin would
fit into), and besides which there's not enough ribbon cable length to plug
it in backwards. I've had it open a couple of times by now.

    With yet more juice, the linux floppies finish loading rescue.gz with no
problem. Fdisk found partition table start/end inconsistencies. I deleted the
partition and put it back in, and it seemed to 'w' okay. DOS still can't find
it however. I'll try mkdosfs and see what happens.

    If I manage to take off on time I'll bring the laptop to the grex lunch.

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