For some last minute twiddling with the P112 project, I ordered some parts
and managed to buy SIP resistor packs with isolated resistors instead of
bussed. Would someone here happen to have two 47-ohm 8-pin bussed SIP
resistors they can send me? I'm trying to avoid paying $5-$10 for
shipping on 20 cents worth of parts.
dgriffi at cs.csubak.edu
So, I decided to buy an IBM 5155 Portable PC on the eBay, in part due to it being a lot cheaper than other 51xx machines I've seen listed recently since I started paying attention. Maybe it'll satisfy my desire for an early IBM PC, and I won't need to spend money on another? Yeah, dream on. :) I'll try putting an XT CF Lite into it; I ordered one in kit form, since soldering on the surface-mount CF socket doesn't intimidate me.
I do have one misgiving about getting this machine, though: I don't like orange CRTs. I mean, I REALLY don't like them. So, at the risk of being virtually tarred and feathered, I shall don my asbestos long johns and ask a sacrilegious question: Is there any prior art regarding swapping out the CRT in a 5155 for one with a less offensive phosphor, such as green, white, etc.?
I'm diving into my flame-proof bunker now... ;)
Mark J. Blair, NF6X <nf6x at nf6x.net>
Just done the light bulb test and get no output at all from the PSU on 5V,
12V, P OK and DC OK, all zero, the fans don't move. And yet, there is no
physical sign of any damage in the PSU.
From: Robert Jarratt [mailto:robert.jarratt at ntlworld.com]
Sent: 28 August 2014 18:53
To: General Discussion: On-Topic and Off-Topic Posts (cctalk at classiccmp.org)
Subject: Mysterious rtVAX 1000 Failure
I have started playing with the rtVAX 1000 I collected last year. It was
running OK when then was a sudden bang and the machine stopped. Not even the
fans will run. There was no smell and no smoke, so I knew immediately that
it can't be the mains filter capacitors, which always fail on these power
I have opened it up and cannot see any damage in the PSU, the CPU, the
memory, or any of the other boards. I am sure it must be the power supply,
but I really can't see any damage. The power supply is one of the ASTEC ones
common in the MicroVAX II.
My first step is going to be to test the PSU with a dummy load using light
bulbs (still haven't built a board for a dummy load) and with the fans
connected, but nothing else. Will also check for ripple at the same time.
There are two outputs from the PSU that I don't fully understand, one is P
OK, I am guessing that means *something* is OK, but not sure what, power
perhaps, but what power?. The other is called LTC, I have no idea what that
one means. Can anyone enlighten me?
Any other ideas?
Working away on the Altair 8800 restoration..
So the display/control board ("d/c") is now installed, and I'm running into
my first roadblock. I ask your understanding in advance, as my familiarity
with digital logic is pretty weak.
This machine has a Processor Tech. MB-1 mainboard in it. Full-width, 16
slots, and some mods I don't understand.
First, there's an LM309 (TO-3 case) mounted to the board, apparently
providing reg'd 5VCD to the normally 8V (un-reg'd) line. Why would that be
there? Every plug-in board I've seen - which isn't all that many,
admittedly - has its own regulator for 5V on-board.
Secondly, on the far left side of the board, there are several columns of
resistors that seem to be doing a couple different things - some are
pulling-up various groups of lines to what seems like 1/2 of VCC, others
are either there for termination or some other unknown function.
All together, close to 100 resistors installed there.. and it's clearly a
mod (at least partly) as a line of 50 new holes was drilled to accommodate
Anyone know what's up with this stuff? Why it's there? At this point, my
sense is that I need to remove all of it, as they don't exist in the
original build - and I may even cut the main board in two - totally lop-off
the leftmost 12 sockets along with the resitors & reg.
As I understand it, there were IBM-branded versions of the Microsoft Macro Assembler(MASM) prior to version 4. I seem to recall seeing one way back when, in the usual small IBM binder in a slip cover box.
What version(s), if any, would have been roughly contemporary with IBM DOS 3.3? Did the MASM version numbers track with DOS releases, or were they independent? I think that I would like to get my hands on one of these. An original copy would be preferable; scans and images would be helpful if I can't find an original.
I have an original IBM DOS 3.3 distribution, still in shrink wrap. I understand that some developer-oriented tools were removed from the 3.3 distribution, and instead came on a utilities diskette with the DOS 3.30 Technical Reference. I see a listing for the book on eBay which I may buy, but it doesn't include the diskettes. If originals or images of the diskettes are available, I'd like to acquire them.
Were there any other IBM-branded development tools for the PC around the time of DOS 3.3?
Mark J. Blair, NF6X <nf6x at nf6x.net>
There were a number of IBM branded development tools at that time. There
were at least two versions of MASM, C, and FORTRAN not to mention the BASIC
compiler. As for contemporary to DOS 3.3 I am not a 100% but they would have
been current if not just the last release.
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of cctalk-request at classiccmp.org
Sent: Wednesday, August 27, 2014 9:00 AM
To: cctalk at classiccmp.org
Subject: cctalk Digest, Vol 132, Issue 56
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> From: Peter Corlett <abuse at cabal.org.uk>
> The recent thread on AB20 reminded me I have a large pile of CDs from the
> that could do with being imaged and uploaded to archive.org.
Ooh. Please share the link when you do get 'em up :)