28 Aug
2025
28 Aug
'25
9:42 a.m.
I finally got the missing keyboard and now it is time to try
and revive it.
A couple quick questions.
It has a board in it called IBM PC INTERFACE with the numbers
170-18-165 and CIL18-16 printed on it. It has a 50 pin connector
on the bracket end. If I take it out the machine dies almost
immediately doing the POST. Tried Google with no luck. Anybody
remember what it is?
Next problem. 1701 error. Light on MFM drive flashes 3 slow
and 4 fast continuously. Being as this machine was known to
work when it was last shut down any suggestions? Could it be
a stiction problem and the disk just isn't spinning up? (Can't
tell by listening as the fan is pretty loud. Not bad just louder
than any good disk I have ever heard.)
And then one other not related to a problem. Being an original
PC owned by users and not geeks is it likely that the floppy
controller is one that can handle other formats (like TRS-80)
and maybe even 8"?
And just to wrap it up. What are the chances of finding an
external drive or even a cable that could be made to connect
to an external drive?
Really hoping to get it to run. Would love to see what the
Psychology Department had on it. At least WordPerfect as there
is one of those function key templates taped on the keyboard.
bill
28 Aug
28 Aug
10:07 a.m.
On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon via cctalk
<cctalk(a)classiccmp.org> wrote:
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. 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
A couple quick questions.
It has a board in it called IBM PC INTERFACE with the numbers
170-18-165 and CIL18-16 printed on it. It has a 50 pin connector
on the bracket end. If I take it out the machine dies almost
immediately doing the POST. Tried Google with no luck. Anybody
remember what it is?
This doesn't sound like any IBM board. Is there a maker's name on it?
And how does the POST die? What error code, etc.
Are there any large chips on the board, or is it all small TTL devices?
Next problem. 1701 error. Light on MFM drive flashes 3 slow
and 4 fast continuously. Being as this machine was known to
work when it was last shut down any suggestions? Could it be
a stiction problem and the disk just isn't spinning up? (Can't
tell by listening as the fan is pretty loud. Not bad just louder
than any good disk I have ever heard.)
I am pretty sure that the only official way to add a hard disk was to
put it in a 5161 expansion cabinet (!) So this must be a 3rd-party
devce, What is the make and model of the hard drive itself? Do you
have a way of powering it up outside the machine? Just power it, with
no ribbon cables connected
And then one other not related to a problem. Being an original
PC owned by users and not geeks is it likely that the floppy
controller is one that can handle other formats (like TRS-80)
and maybe even 8"?
The original IBM floppy controller is a 3/4 length card. Theres an
edge connector at the front for the ribbon cable to the internal
drives and a DC37 socket on th bracket for the external drives. Mostly
small ICs with one 40 pin device (NEC 765 or Intel 8272, they're
essentially the same).
This board is strictly double density, standard data rate only. It
won't do 8" data rates. It won't do single density.
And just to wrap it up. What are the chances of
finding an
external drive or even a cable that could be made to connect
to an external drive?
Very easy to make the cable using an IDC DC37 plug, 34 way ribbon
cable and the sockets/edge connectors to fit your drives. I am sure
there are instructions on the web.
-tony
11:29 a.m.
On 8/28/2025 1:07 PM, Tony Duell wrote:
Nothing recognizable. A really small jbl in one spot but not like it
was a company logo. Maybe the guy who designed the board. There is
Rev. 1 along one edge.
Western Digital WDX-GEN,
Interesting. I always thought the original PC controllers could do
all of it and it wasn't until the 3.5 came out with a suitable
controller that we lost all that. So, now that I have an ISA MB
again is there any controllers available that can do everything?
I think there used to be an Adaptec that did it.
Guess I need to get it working and find a suitable controller
before worrying about it.
bill
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.
A couple quick questions.
It has a board in it called IBM PC INTERFACE with the numbers
170-18-165 and CIL18-16 printed on it. It has a 50 pin connector
on the bracket end. If I take it out the machine dies almost
immediately doing the POST. Tried Google with no luck. Anybody
remember what it is?
This doesn't sound like any IBM board. Is there a maker's name on it? 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.
Are there any large chips on the board, or is it all small TTL devices?
Looks to be all TTL chips and two fairly large jumper blocks.
Next problem. 1701 error. Light on MFM drive flashes 3 slow
and 4 fast continuously. Being as this machine was known to
work when it was last shut down any suggestions? Could it be
a stiction problem and the disk just isn't spinning up? (Can't
tell by listening as the fan is pretty loud. Not bad just louder
than any good disk I have ever heard.)
I am pretty sure that the only official way to add a hard disk was to
put it in a 5161 expansion cabinet (!) So this must be a 3rd-party
devce, 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.
Do you
have a way of powering it up outside the machine? Just power it, with
no ribbon cables connected
Not yet but I will once I have it out. I have tried listening as
close as I can get and I don't think the disk is spinning. Sure
sounds like stiction to me. And I no longer have my disk mallet as
broke quite some time ago. :-) Would like to get it out and try
cycling the power to it a few times and maybe even using the heat
gun. Ah, the things we dealt with back in the day. Will not be
a surprise to me if it is a Seagate Disk.
And then one other not related to a problem. Being an original
PC owned by users and not geeks is it likely that the floppy
controller is one that can handle other formats (like TRS-80)
and maybe even 8"?
The original IBM floppy controller is a 3/4 length card. Theres an
edge connector at the front for the ribbon cable to the internal
drives and a DC37 socket on th bracket for the external drives. Mostly
small ICs with one 40 pin device (NEC 765 or Intel 8272, they're
essentially the same).
This board is strictly double density, standard data rate only. It
won't do 8" data rates. It won't do single density. And just to wrap it up. What are the chances of
finding an
external drive or even a cable that could be made to connect
to an external drive?
Very easy to make the cable using an IDC DC37 plug, 34 way ribbon
cable and the sockets/edge connectors to fit your drives. I am sure
there are instructions on the web.
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. 
1:45 p.m.
I got this one from IBM, I used to work there just after they stopped
selling them. It's pretty close to original stock including an IBM 256KB
RAM card what could go in a short slot. IBM had a number of cards then
that fit in the shorter slots.
https://www.vintagecomputer.net/ibm/5155/
Bill
On Thu, Aug 28, 2025 at 3:51 PM Tony Duell via cctalk <cctalk(a)classiccmp.org>
wrote:
On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon via
cctalk
<cctalk(a)classiccmp.org> 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.
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:
> On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon via cctalk
> <cctalk(a)classiccmp.org> wrote:
>>
>>
>> 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.
That explains the weird little cable stretching over some of the boards
and getting in the way. :-)
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.
29 Aug
29 Aug
6:15 a.m.
On 8/28/2025 3:03 PM, Tony Duell wrote:
Which is what you'd expect with no bootable disk in the system.
>> 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.
OK. I took it all apart. Miniscribe disk. With it out I hooked it
up to an ext5ra PSU I had and toggled the power on and off a bunch
of times. It finally spun up and the blinky LED is not longer blinky.
On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon via
cctalk
<cctalk(a)classiccmp.org> wrote:
Interesting. Not coax.
On 8/28/2025 1:07 PM, Tony Duell wrote:
It's normally yellow and black twisted pair. 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.
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.
More interesting info. I was not aware of there being any priorities
on the IBM PC bus. I thought all the slots were the same. At least
in the past when I last worked with PC's at the hardware level (a
really long time ago when they were new) I never saw any needed
ordering of the cards.
Here's mine, satrtng from the PSU:
Slot 1: That CIL thing (now that I have booted without it I think
it was an interface to some weird lab device,
They had similar interfaces in their Apple ]['s
as well.)
Slot 2: Memory
Slot 3: Floppy ( a long card )
Slot 4: HD Controller (WDX-GEN)
Slot 5: Video-Serial-Paralel
Slot 6: Empty
Slot 7: Empty
Slot 8: Empty
Recommended ordering?
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.
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.
Ended out having to take the screws all the way out so I could
wiggle them a lot. Very snug fit, especially the fascia.
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).
Pfft. Who needs manuals when you have google and youTube. :-)
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.
I guess next is to spray all the edge connectors and slots with DeOxit
and out it all back together.
bill
7:30 a.m.
On Fri, Aug 29, 2025 at 2:26 PM Bill Gunshannon via cctalk
<cctalk(a)classiccmp.org> wrote:
Apart from slot 8 in an IBM PC/XT motherboard (which this is), all
slots are the same. The ordering I gave is simply how the machine was
shipped from IBM, it makes sense as it gives the neatest run of video
and floppy cables.
FWIW, my 5155 has the following cards :
1 CGA video
2 Data Acquisition/Control
3 Floppy controller
4 and 5 Async serial (modified so you can use either RS232 or current
loop without opening the case)
6 and 7 Parallel printer (modified to have bidirectional data lines)
I've also done the motherboard mod to have 640k RAM there
If the floppy drive is the orginal Qumetrak then there are little
plastic spacers on the screws to fit into the recesses on the drive
chassis casting. One of mine was missing so I milled a replacement
from plastic block
Well I do. To the extent that I bought all the Techrefs from IBM many
years ago and have a shelf of them upstairs. I've also downloaded the
bitsavers ones of course. Along with manuals for literally hundreds of
other machines. Maybe you can find a failed component on your own but
I am stupid enough to need the schematics.
I have never been able to learn how to do anything from a video, for
me it's the most ridiculous way to present such information. And
there's so much misinformation on the web (in all fields) that I
prefer to start from the original manuals rather than somebody's
version of whatever
-tony
On 8/28/2025 3:03 PM, Tony Duell wrote:
Not in the origiinal IBM version.
On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon
via cctalk
<cctalk(a)classiccmp.org> wrote:
Interesting. Not coax.
On 8/28/2025 1:07 PM, Tony Duell wrote:
It's normally yellow and black twisted pair. On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon
via cctalk
<cctalk(a)classiccmp.org> wrote:
>
>
> 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.
That explains the weird little cable stretching over some of the boards
and getting in the way. :-)
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.
More interesting info. I was not aware of there being any priorities
on the IBM PC bus. I thought all the slots were the same. At least in the past when I last worked with PC's at the
hardware level (a
really long time ago when they were new) I never saw any needed
ordering of the cards.
Here's mine, satrtng from the PSU:
Slot 1: That CIL thing (now that I have booted without it I think
it was an interface to some weird lab device,
They had similar interfaces in their Apple ]['s
as well.)
Slot 2: Memory
Slot 3: Floppy ( a long card )
That may be the original IBM card
Slot 4: HD Controller (WDX-GEN)
Slot 5: Video-Serial-Paralel
Cerrtainly not IBM!
Slot 6: Empty
Slot 7: Empty
Slot 8: Empty
Recommended ordering?
Whatever fits in the case and lets the cables run neatly.
> 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.
OK. I took it all apart. Miniscribe disk. With it out I hooked it up to an ext5ra PSU I had and toggled the power on and
off a bunch
of times. It finally spun up and the blinky LED is not longer blinky.
It may work for the moment. I'd grab any interesting data off it ASAP though.
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.
Ended out having to take the screws all the way out so I could
wiggle them a lot. Very snug fit, especially the fascia.
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).
Pfft. Who needs manuals when you have google and youTube. :-)
7:41 a.m.
On 8/29/2025 10:30 AM, Tony Duell wrote:
Apart from slot 8 in an IBM PC/XT motherboard (which this is), all
slots are the same. The ordering I gave is simply how the machine was
shipped from IBM, it makes sense as it gives the neatest run of video
and floppy cables.
FWIW, my 5155 has the following cards :
1 CGA video
2 Data Acquisition/Control
3 Floppy controller
4 and 5 Async serial (modified so you can use either RS232 or current
loop without opening the case)
6 and 7 Parallel printer (modified to have bidirectional data lines)
I've also done the motherboard mod to have 640k RAM there
OK, Slot 8 is not convenient so it can remain empty. I'll
figure out an order based on the cabling.
Oh, based on experience I expect it will work fine as long as I
don't leave it turned off for 20 years again. :-)
If the floppy drive is the orginal Qumetrak then there are little
plastic spacers on the screws to fit into the recesses on the drive
chassis casting. One of mine was missing so I milled a replacement
from plastic block
It's TEAC 55. Only one of those spacers was there.
Well I do. To the extent that I bought all the Techrefs from IBM many
years ago and have a shelf of them upstairs. I've also downloaded the
bitsavers ones of course. Along with manuals for literally hundreds of
other machines. Maybe you can find a failed component on your own but
I am stupid enough to need the schematics.
I have never been able to learn how to do anything from a video, for
me it's the most ridiculous way to present such information. And
there's so much misinformation on the web (in all fields) that I
prefer to start from the original manuals rather than somebody's
version of whatever
Sorry, I was just trying to be humorous. I have piles of paper manuals
for most of my computers. As for failed components, I have never and
would never waste time trying that on a PC class machine. Now, on a
PDP or VAX.... Still have an oscilloscope.
bill
On Fri, Aug 29, 2025 at 2:26 PM Bill Gunshannon via
cctalk
<cctalk(a)classiccmp.org> wrote:
Just a comment that I found it interesting. Surprised there
isn't a lot of noise on the screen.
On 8/28/2025 3:03 PM, Tony Duell wrote:
Not in the origiinal IBM version. On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon
via cctalk
<cctalk(a)classiccmp.org> wrote:
Interesting. Not coax.
On 8/28/2025 1:07 PM, Tony Duell wrote:
> On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon via cctalk
> <cctalk(a)classiccmp.org> wrote:
>>
>>
>> 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.
That explains the weird little cable stretching over some of the boards
and getting in the way. :-)
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.
More interesting info. I was not aware of there being any priorities
on the IBM PC bus. I thought all the slots were the same. At least in the past when I last worked with PC's at
the hardware level (a
really long time ago when they were new) I never saw any needed
ordering of the cards.
Here's mine, satrtng from the PSU:
Slot 1: That CIL thing (now that I have booted without it I think
it was an interface to some weird lab device,
They had similar interfaces in their Apple ]['s
as well.)
Slot 2: Memory
Slot 3: Floppy ( a long card )
That may be the original IBM card
Slot 4: HD Controller (WDX-GEN)
Slot 5: Video-Serial-Paralel
Cerrtainly not IBM!
Slot 6: Empty
Slot 7: Empty
Slot 8: Empty
Recommended ordering?
Whatever fits in the case and lets the cables run neatly. > 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.
OK. I took it all apart. Miniscribe disk. With it out I hooked it up to an ext5ra PSU I had and toggled the power
on and off a bunch
of times. It finally spun up and the blinky LED is not longer blinky.
It may work for the moment. I'd grab any interesting data off it ASAP though.
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.
Ended out having to take the screws all the way out so I could
wiggle them a lot. Very snug fit, especially the fascia.
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).
Pfft. Who needs manuals when you have google and youTube. :-)
10:07 a.m.
On Fri, Aug 29, 2025 at 3:51 PM Bill Gunshannon via cctalk
<cctalk(a)classiccmp.org> wrote:
[Video cable]
Not in the origiinal IBM version.
Just a comment that I found it interesting. Surprised there
isn't a lot of noise on the screen.
In the original it's quite short. And of course it's a low-impedance
connection, terminated with 75 ohms at the monitor end.
The main 'noise' on the screen is due to the chroma subcarrier which
does appear on solid regions.
Another part of your machine that's been swapped out at some point.
Well I do. To the extent that I bought all the Techrefs from IBM many
years ago and have a shelf of them upstairs. I've also downloaded the
bitsavers ones of course. Along with manuals for literally hundreds of
other machines. Maybe you can find a failed component on your own but
I am stupid enough to need the schematics.
I have never been able to learn how to do anything from a video, for
me it's the most ridiculous way to present such information. And
there's so much misinformation on the web (in all fields) that I
prefer to start from the original manuals rather than somebody's
version of whatever
Sorry, I was just trying to be humorous. I have piles of paper manuals
for most of my computers.
Unfortunately I've seen the results of people following ill-informed
instructions on the web, particularly with audio amplifiers, etc. The
results sometimes end up on my bench and I have a lot more work to do
than if I simply had to find the original fault.
It's
normally yellow and black twisted pair.
Interesting. Not coax. If the floppy
drive is the orginal Qumetrak then there are little
plastic spacers on the screws to fit into the recesses on the drive
chassis casting. One of mine was missing so I milled a replacement
from plastic block
It's TEAC 55. Only one of those spacers was there.
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).
Pfft. Who needs manuals when you have google and youTube. :-) As for failed components, I have never and
would never waste time trying that on a PC class machine.
I do, particularly on a machine that's not just another random clone,
for example a genuine IBM one. It's as historic as any other classic
computer. And I am much more likely to have the right IC in stock than
the right replacement board.
Now, on a
PDP or VAX.... Still have an oscilloscope.
Just one 'scope?
-tony
10:56 a.m.
On 8/29/2025 1:07 PM, Tony Duell wrote:
Sorry, I was just trying to be humorous. I have piles of paper manuals
for most of my computers.
Unfortunately I've seen the results of people following ill-informed
instructions on the web,
Now I have to tell my two latest examples. One good, one bad.
I had to replace the drive belt on my John Deere lawn tractor.
I watched a video on youTube. Said easy 15 minute job. 3 days
later and after buying yet another power tool I didn't have I
finished it up. One of the biggest delays was getting a bolt
back into the transmission casing. I could find no way my hand
would fit in the space where it had to go. The video was done
by a woman who, obviously, had a much smaller hand.
But there is a good side, too. I need to replace the awning on
my camper. The awning manufacturer has an excellent and very
professional video on how to do it.
The trick seems to be find real examples of what you want
to do and not just some "influencer".
Used to have three (one was a Heathkit I built when I was about 12) but
now it's just one that fits in my pocket.
bill
On Fri, Aug 29, 2025 at 3:51 PM Bill Gunshannon via
cctalk
<cctalk(a)classiccmp.org> wrote:
[Video cable]
Just a comment that I found it interesting. Surprised there
isn't a lot of noise on the screen.
In the original it's quite short. And of course it's a low-impedance
connection, terminated with 75 ohms at the monitor end.
The main 'noise' on the screen is due to the chroma subcarrier which
does appear on solid regions.
Another part of your machine that's been swapped out at some point.
Guess it's not as IBM as I thought. :-)
> It's normally yellow and black twisted pair.
Interesting. Not coax.
Not in the origiinal IBM version. If the
floppy drive is the orginal Qumetrak then there are little
plastic spacers on the screws to fit into the recesses on the drive
chassis casting. One of mine was missing so I milled a replacement
from plastic block
It's TEAC 55. Only one of those spacers was there.
>
> 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).
Pfft. Who needs manuals when you have google and youTube. :-)
Well I do. To the extent that I bought all the Techrefs from IBM many
years ago and have a shelf of them upstairs. I've also downloaded the
bitsavers ones of course. Along with manuals for literally hundreds of
other machines. Maybe you can find a failed component on your own but
I am stupid enough to need the schematics.
I have never been able to learn how to do anything from a video, for
me it's the most ridiculous way to present such information. And
there's so much misinformation on the web (in all fields) that I
prefer to start from the original manuals rather than somebody's
version of whatever particularly with audio
amplifiers, etc. The
results sometimes end up on my bench and I have a lot more work to do
than if I simply had to find the original fault.
Sadly, my days of doing that stuff are rapidly running out.
As for failed components, I have never and
would never waste time trying that on a PC class machine.
I do, particularly on a machine that's not just another random clone,
for example a genuine IBM one. It's as historic as any other classic
computer. And I am much more likely to have the right IC in stock than
the right replacement board. Now, on a
PDP or VAX.... Still have an oscilloscope.
Just one 'scope? 
3:30 p.m.
> It's TEAC 55. Only one of those spacers was
there.
On Fri, 29 Aug 2025, Tony Duell via cctalk wrote:
Another part of your machine that's been swapped
out at some point.
But, arguably a GOOD swap,
The Teac 55 (55B?) is a good drive.
The Qumetrak 142 (5155 and PC/Jr) is not.
I had almost as many failures with it as with the BASF 2/3 height drive.
The Qumetrah 142 is SLOW steppoing track to track. Slow enough that one
of the reasons ihat IBM released 2.10 included setting a longer track to
track time
--
Grumpy Ol' Fred cisin(a)xenosoft.com
7:45 p.m.
On Fri, Aug 29, 2025 at 11:36 PM Fred Cisin via cctalk
<cctalk(a)classiccmp.org> wrote:
There are many versions of the Teac FD55B which seem to share only
similar model numbers and specifications. Some are better than others.
> It's TEAC 55. Only one of those spacers
was there.
On Fri, 29 Aug 2025, Tony Duell via cctalk wrote:
Another part of your machine that's been
swapped out at some point.
But, arguably a GOOD swap,
The Teac 55 (55B?) is a good drive. The Qumetrak 142 (5155 and PC/Jr) is not.
I had almost as many failures with it as with the BASF 2/3 height drive.
What failed? I've had the ones in my 5155 totally apart and they don't
seem difficult to repair. Electronic faults should be easier to fix
than those on the Teac due to the latter's use of custom ICs.
The Qumetrah 142 is SLOW steppoing track to track. Slow enough that one
of the reasons ihat IBM released 2.10 included setting a longer track to
track time
According to the Techref, it's 6ms step time, which seems reasonable.
And I have verified (using a drive exerciser) that the ones in my 5155
will do that.
-tony
3:44 p.m.
A further, [probably unneeded] clarification,
One slot is different. The othersare all alike, BUT the 5155 had stuff in
the way (unlike the similar Compaq) that forced placing boards according
to length.
Some boards won't work in the different slot.
To discourage people from putting other boards in that slot, IBM provided
a "FREE!" Asynch (RS232, current loop) board, already installed in that
slot, so that the user would not even have to install it. Apparently, due
to the immediate third party market of multi-function cards when the PC
came out, IBM sold much fewer ot the asynch cards than they had expected,
making giving away a "FREE!" card in the different slot economical.
The IBM FDC board was hard wired for 5.25" MFM. The changes needed for
others were not extremely major (Flagstaff Engineering, at one point had
an IBM FDC board, with lots of colored wires, to do 8" SSSD.)
There existed numerous after-market FDC boards with capabilities of FM,
MFM, and other data transfer rates. The best known of those was the
Micro Solutions ("Uniform") "Compaticard". But, there were even
generic
ones. And, of course, additional software was needed to handle anything
other than the PC-DOS/MS-DOS 5.25" MFM with IBM/WD traack and sector
structure..
--
Grumpy Ol' Fred cisin(a)xenosoft.com
XenoSoft http://www.xenosoft.com
On Fri, 29 Aug 2025, Bill Gunshannon via cctalk wrote:
>
>
> On 8/28/2025 3:03 PM, Tony Duell wrote:
>> On Thu, Aug 28, 2025 at 7:46 PM Bill Gunshannon via cctalk
>> <cctalk(a)classiccmp.org> wrote:
>>>
>>>
>>>
>>> On 8/28/2025 1:07 PM, Tony Duell wrote:
>>>> On Thu, Aug 28, 2025 at 5:51 PM Bill Gunshannon via cctalk
>>>> <cctalk(a)classiccmp.org> wrote:
>>>>>
>>>>>
>>>>> 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.
>>>
>>> That explains the weird little cable stretching over some of the boards
>>> and getting in the way. :-)
>>
>> It's normally yellow and black twisted pair.
>
> Interesting. Not coax.
>
>>
>> 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.
>
> More interesting info. I was not aware of there being any priorities
> on the IBM PC bus. I thought all the slots were the same. At least
> in the past when I last worked with PC's at the hardware level (a
> really long time ago when they were new) I never saw any needed
> ordering of the cards.
>
> Here's mine, satrtng from the PSU:
> Slot 1: That CIL thing (now that I have booted without it I think
> it was an interface to some weird lab device,
> They had similar interfaces in their Apple ]['s
> as well.)
> Slot 2: Memory
> Slot 3: Floppy ( a long card )
> Slot 4: HD Controller (WDX-GEN)
> Slot 5: Video-Serial-Paralel
> Slot 6: Empty
> Slot 7: Empty
> Slot 8: Empty
>
> Recommended ordering?
>
>>
>>
>>>
>>>>
>>>> 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.
>>
>> Which is what you'd expect with no bootable disk in the system.
>>
>>
>>>> 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.
>
> OK. I took it all apart. Miniscribe disk. With it out I hooked it
> up to an ext5ra PSU I had and toggled the power on and off a bunch
> of times. It finally spun up and the blinky LED is not longer blinky.
>
>>
>> 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.
>
> Ended out having to take the screws all the way out so I could
> wiggle them a lot. Very snug fit, especially the fascia.
>
>>
>> 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).
>
> Pfft. Who needs manuals when you have google and youTube. :-)
>
>>
>> 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.
>
>
> I guess next is to spray all the edge connectors and slots with DeOxit
> and out it all back together.
>
> bill
>
23
days inactive
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12 comments
4 participants
participants (4)
-
Bill Degnan -
Bill Gunshannon -
Fred Cisin -
Tony Duell