28 Dec
1998
28 Dec
'98
10:07 a.m.
Most likely you either shorted the mains side of the
PSU to something on
the secondary side, or you messed up the regulation circuitry, probably
the former. The damage sounds like what you'd expect with 110V on a board
of TTL...
Ouch!. It's even possible that you've blown chips in the printer....
The one paper clip fell across the little clip that supplies 110v to the
main PSU. That's what blew the breaker. I tested the printer on my Tandy
1000, and it still works.
There are 2 power supplies in the Model 3 - one on the
side of the drive
tower, one on the front of the logic cage. Which one got zapped ? The one
on the drive tower supplies the drives and the FDC board, the one on the
logic cage supplies the CPU board, RS232 board and video board.
Neither. The main M/B got zapped. I can power it up w/o MB in it, the
video lights up, and the drives go for about 1 second on power on.
You might also be looking for a second PSU and drives :-(. This is a
machine to rebuild slowly - get working PSUs (and test them on dummy
load), then add just the CPU board and video and check that it goes into
ROM basic correctly. Then add the floppy controller and drives. Finally
add the RS232 board.
I've fixed model3's and 4's, but never one that this has happened to.
Everything's fine but the CPU board and RS-232 card.
A couple of other suggestions. A model 4 CPU board (non-gate array only?)
will drop in there, and will run all model 3 software. So that's
something to look for. The other possibility is to find a cassette-only
model 3 or model 4 and move your (working) FDC, tower, drives and second
PSU into in.
I was thinking about that, but won't I need a new keyboard, too? I really
don't want to do that, because I just rebuilt every switch (they're not the
rubber cup type) a few months ago.
The upgrade is (IIRC) just adding columns of 4116 chips. Worth bring it
up to 48K anyway when you have the case apart.
Well, the RAM banks on the fried board were all full, so I guess it had 48k.
--
-Jason Willgruber
(roblwill(a)usaor.net)
ICQ#: 1730318
<http://members.tripod.com/general_1>