28 Aug
2025
28 Aug
'25
12:03 p.m.
On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon via cctalk
<cctalk(a)classiccmp.org> wrote:
Which is what you'd expect with no bootable disk in the system.
I seem to remember you need a 5.5mm or 7/32" spanner and nutdriver to
do that. You take off the earthing bracket on the right hand side of
the drives towards the rear, then loose the other 3 screws on each
drive and slide them out backwards.
There are some useful manuals on bitsavers. The Technical Reference
for the PC/XT and portablePC gives the motherboard schematic and BIOS
source. The Options and Adapters volume 1 gives the schemaitcs for the
drives and monitor. And volume 2 gives the CGA and floppy controller
schematics (and lots of others).
Finally there's the Hardware Maintenance and Service manual for the
portablePC. This is a 'boardswaper guide' but it tells you what to
unplug and what to unscrew to get things out.
-tony
On 8/28/2025 1:07 PM, Tony Duell wrote:
It's normally yellow and black twisted pair.
As standard, the CGA card goes in slot 1, closest to the PSU. Floppy
controller in slot 3. This leaves slot 2 as an empty full-length slot
and slots 4-7 as half-length ones. Slot 8 is not really useable. Being
an XT motherboard, the card there has to assert the buffer enable pin
on reads. The only IBM card that will do that is the async serial one.
And it's about 1/4" too long to fit, it fouls the power connectors on
the drives.
On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon
via cctalk
<cctalk(a)classiccmp.org> wrote:
That explains the weird little cable stretching over some of the boards
and getting in the way. :-)
I finally got the missing keyboard and now it is time to try
and revive it.
I restored one some months back. Mine is 100% IBM boards and options....
The portablePC has a normal XT motherboard in it. The standard video
board is the CGA one, with the composite output (on the 4 pin
connector originally designed for an RF modulator) feeding the
internal amber moniitor. This is actually a Zenith unit.
Note that if you want to remove or open up the monitor and PSU you
need Bristol Spline tools.
Does it make me a true geek if I say that I actually have a set of them?
And tamperprrof Torx
for the PSU cover. I
had to take the latter apart, the mains input filter capaciitors were
being antisocial and breaking down. I replaced them before they filled
the worshop with magic smoke
PSU seems fine.
And how does the POST die? What error code, etc.
Well, lets confuse things even more. Took th3e card out again and
the system tested all 640K and went into BASIC. What
is the make and model of the hard drive itself?
No idea yet as it is buried in the system below the floppy. But I
plan on pulling it out as soon as I figure out the mounting scheme
for the disks.