27 Aug
2014
27 Aug
'14
2:14 a.m.
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>
http://www.nf6x.net/
27 Aug
27 Aug
12:09 p.m.
Mark J. Blair wrote:
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... ;)
I have a rather large collection of these. I have one that had a dead
monitor and a bunch of parts missing that I've been slowly working into
a somewhat more modern setup.
Just about the first thing I did was to retrofit it with a color screen.
Peace... Sridhar
1:34 p.m.
On Aug 27, 2014, at 09:09 , Sridhar Ayengar <ploopster at gmail.com> wrote:
I have a rather large collection of these. I have one
that had a dead monitor and a bunch of parts missing that I've been slowly working
into a somewhat more modern setup.
Just about the first thing I did was to retrofit it with a color screen.
That's an interesting upgrade. Was it hard to find a CGA-compatible monitor that fit
in the case well?
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
3:39 p.m.
Mark J. Blair wrote:
On Aug 27, 2014, at 09:09 , Sridhar Ayengar <ploopster at gmail.com> wrote:
I got one with "roughly" the same size. There was some modification
involved. But, if memory serves, nothing I couldn't do with my cordless
Dremel.
Peace... Sridhar
I have a rather large collection of these. I
have one that had a dead monitor and a bunch of parts missing that I've been slowly
working into a somewhat more modern setup.
Just about the first thing I did was to retrofit it with a color screen.
That's an interesting upgrade. Was it hard to find a CGA-compatible monitor that fit
in the case well? 
4:43 p.m.
On Wed, 27 Aug 2014, Mark J. Blair wrote:
That's an interesting upgrade. Was it hard to find
a CGA-compatible
monitor that fit in the case well?
If you find a monitor that will physically fit, including power, etc., it
does NOT need to be CGA.
The "Portable PC" used a stock? CGA card, which could be replaced with
EGA or VGA.
Howzbout: would it be practical to fit a very small LED VGA monitor?
5:17 p.m.
On Aug 27, 2014, at 13:43 , Fred Cisin <cisin at xenosoft.com> wrote:
Howzbout: would it be practical to fit a very small
LED VGA monitor?
Possibly, but I don't want to modify the machine that much. I just don't like the
orange phosphor, is all, so if I can find a suitable green CRT that would swap easily, I
might think about swapping it.
Not that I plan to replace the CGA card, but were EGA and VGA cards available for the
8-bit slots? I thought those appeared in the AT era, and so I just assumed they were 16
bit cards.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
7:23 p.m.
On Wed, 27 Aug 2014, Mark J. Blair wrote:
Not that I plan to replace the CGA card, but were EGA
and VGA cards
available for the 8-bit slots? I thought those appeared in the AT era,
and so I just assumed they were 16 bit cards.
They were readily available.
8 bit EGA was very common.
I have no idea how easily you can find them.
28 Aug
28 Aug
5:36 p.m.
Not that I plan to replace the CGA card, but were EGA
and VGA cards
available for the 8-bit slots? I thought those appeared in the AT era,
and so I just assumed they were 16 bit cards.
The original IBM EGA card was an 8 bit device.
I believe there were VGA cards that would work in 8 bit slots. Ofte they
had the 16 bit connectors, but either had a jumper/switch to select 8 bit
operation or auto-detected what sort of slot they were in.
-tony
27 Aug
27 Aug
1:03 p.m.
On Aug 26, 2014, at 11:14 PM, Mark J. Blair <nf6x at nf6x.net> wrote:
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... ;)
Actually as I recall there were prototypes of that system build with 3 different colored
CRT phosphors (white, green and amber). I'm not sure in the end why amber was chosen.
But I remember having/working with both amber and green screen versions and I saw folks
with white screens. So, while others may scream, I don't think it would be too much
of an affront since internally IBM was trying to decide which one to use.
TTFN - Guy
2:05 p.m.
On Aug 27, 2014, at 10:03 , Guy Sotomayor <ggs at shiresoft.com> wrote:
Actually as I recall there were prototypes of that
system build with 3 different colored CRT phosphors (white, green and amber). I'm not
sure in the end why amber was chosen. But I remember having/working with both amber and
green screen versions and I saw folks with white screens. So, while others may scream, I
don't think it would be too much of an affront since internally IBM was trying to
decide which one to use.
Interesting! I haven't done a CRT swap before. Are good tubes suitable for that
monitor hard to find these days?
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
3:56 p.m.
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 s pend 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 don't know how much you know about the internals of the IBM5155. There
is a noraml PC/XT motherbosrd in there, so you cna do the '640K mod and
put all the RAM on the motherboard. The video card is a standard CGA
card, the disk controller is the standard PC one linked to a pair of
'slimline' drives [1]. Essentially the only odd bits (electircally) are
hte pSU and monitor.
[1] Grumpy Old Fred has mentioned htis in the past, but IBM were really
sill here. The drive in the 5155 is not the same as the 360K drive for
the PC/AT. Worse than tht, the 360K drive for the PC/AT has a '*' on the
facepalte (to tell you it's not 1.2M), the drive i nthe 5155 doesn't
Quite why IBM marked the drives in this way is beyond 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.?
Byy 'CRT' do yuo mean what it think of as a CRT -- the glass thing full
off vacuum -- or do you mean the ocmplete monitor?
The monitor is actually a composite-video input monochrome thing, made I
think by Zenith (at least the schemaitc in the Techref has Zentih
house-codes oon the horizontal oscillator IC, etc). Unforutnately the
TechRef doesn't give the part number for the CRT, and I've not got my
5155 in bits at the moment (I can do so if you like) but I am pretty sure
it's a standard 7 pin device wit ha 12V heater.
If you can find a simialr CRT (same dimentions, same type of base, it is
very liekyl to work. CRTs are very generic in these small mono monitors.
Persoonally, I'd want to keep the monitor PCB, etc. It is part of the
design of the machien. And just swap the CRT itself.
If yopu can't find a CCRT that will fit/work, well, it is a normal CGA
card driving it. The intetnal monitor plugs into the 4 pin header on the
PCB that was originally intended for a TV modualtor. You still ahve the
RCA phoono composite socket and the DE9 RGBI socket on the bracket. You
could connect an external monitor there.
-tony
4:40 p.m.
On Aug 27, 2014, at 12:56 , Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I don't know how much you know about the internals
of the IBM5155. There
is a noraml PC/XT motherbosrd in there, so you cna do the '640K mod and
put all the RAM on the motherboard. The video card is a standard CGA
card, the disk controller is the standard PC one linked to a pair of
'slimline' drives [1]. Essentially the only odd bits (electircally) are
hte pSU and monitor.
I've been reading up on them since last night. My current plan is to go with a fairly
original/standard configuration, with the addition of an XT CF Lite card and possibly a
RAM upgrade. And possibly a CRT replacement.
Byy 'CRT' do yuo mean what it think of as a
CRT -- the glass thing full
off vacuum -- or do you mean the ocmplete monitor?
Yes, I meant swapping the actual cathode ray tube for one with green/white/blue phosphor,
leaving the rest of the monitor electronics intact.
Persoonally, I'd want to keep the monitor PCB,
etc. It is part of the
design of the machien. And just swap the CRT itself.
Yes, that's what I had in mind.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
28 Aug
28 Aug
5:28 p.m.
I've been reading up on them since last night. My current plan is to
go with a fairly original/standard configuration, with the addition of
an XT CF Lite card and possibly a RAM upgrade. And possibly a CRT
replacement.
AS I mentioned last night, there's a standard IBM 5160 (XT) motherboard
in there. It's a little hard to get out (IIRC) you have to remvoe at
least one of the disk drives to get to a fixing screw o na bracket), but
when you have it out you can fit 640K RAM on the motherboard. Basically,
you put 256K*1 DRAMs in banks 0 and 1, 64K*1 DRAMs in banks 2 and 3, fit
a 74S158 (or 74F158) multiplexer chip in the unused socket near the front
of the board, solder a link between pads E1 and E2 and set the DIP
switches for all 4 banks of RAM filled. It'll then have 640K.
-tony
27 Aug
27 Aug
4:23 p.m.
One thing I forgot to metion in my last reply...
To take the monitor section of the 5155 apart you need Bristol Spline
keys. These are not common, at least not in the UK. Torx drivers and Allen
keys will not fit.
You need tamperproof torx tools to take the PSU apart, BTW.
-tony
4:46 p.m.
On Aug 27, 2014, at 13:23 , Tony Duell <ard at p850ug1.demon.co.uk> wrote:
One thing I forgot to metion in my last reply...
To take the monitor section of the 5155 apart you need Bristol Spline
keys. These are not common, at least not in the UK. Torx drivers and Allen
keys will not fit.
Thanks for the warning! That would have taken me by surprise. I don't think
they're common anywhere... but I'm also a military radio collector with a bunch of
Collins gear, so I already have a set of Bristol Spline keys!
You need tamperproof torx tools to take the PSU apart,
BTW.
I may already have the right ones, and if not then I'll order them from McMaster-Carr.
I'll want to dig in there to make sure that none of those danged Rifa brand
paper-dielectric EMI filtering caps are lurking inside.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/
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