As has been the case with other participants my Retrochallenge has been somewhat blown off course by outside events. Still I had some initial fun tinkering with the Samsung PenMaster. Although it didn’t provide much of a challenge it was interesting to look back at the false start tablet computing had with pen based computing.
I then moved on to the IBM 5140 which is a machine I really enjoyed using. Its slightly absurd design with its expansion ‘slices’ leading to an ever-increasing footprint is tempered by its overall solidity and great keyboard. I would very much like to obtain an original monitor and I noticed today someone is selling new in the box printer units for it.
Arriving too late in the day for me to get my teeth into it was an Anderson Jacobson ADC 212 acoustic coupler. I had hoped to use it to connect to either mine or Urbancamo’s new BBS but time has run out. Getting the coupler working may form the basis of my next challenge.
I’m now looking forward to catching up on the other participant’s entries, some of which are clearly very impressive.
The non backlit LCD display on the 5140 is poor to say the least, low contrast and dim. Fortunately I have the expansion ‘slice’ that offers CGA and composite outputs, unfortunately it smoked alarmingly the first time I powered it up. However after taking it apart and not being able to find any obvious damage I decided to risk it and plug it in again. I don’t think I’ve got any monitors capable of hooking up to the CGA output so I decided to try the composite out. I wasn’t expecting it to work but was pleasantly surprised when my trusty IIyama flat panel picked up a signal.
Initially it looked pretty awful, all sorts of convergence issues and generally pretty fuzzy. The IIyama however offers a lot of adjustment options and after fiddling with the brightness and contrast, reducing the colour to zero and altering the sharpness I had a pretty useable image. I then remembered you can alter the output via the Application Selector supplied with PC-DOS. Sure enough once I’d changed it from colour to mono I was pleasantly surprised by the quality of the composite output. After a bit more fiddling I was even able to achieve a cool retro amber look by altering the colour temperature.
I’ve been trying out the expansion units that came with the 5140 and clip on to the back of the main machine. One provides parallel and serial ports and the other is for connecting a monitor. Unfortunately I had a ‘magic smoke’ incident with the later unit after powering up the machine. It was a bit of an ‘oh shit’ moment as initially I didn’t notice it but caught a whiff of the tell tale stench before spotting the smoke rising from the unit and shutting it down. I haven’t opened it up yet to see what the damage is but hopefully it’s repairable.
The expansion bus on the 5140 uses 8-bit ISA architecture. At the rear of the unit is a single 72 pin edge connector which is repeated on the back of each expansion unit. Once attached the expansion units give the machine a very odd look, especially if you also attach the printer unit which results in the 5140 almost doubling in length.
Theoretically you could create some kind of hack with an old unit and hook up an HDD but that’s well beyond my level of tinkering.
The serial port on the interface expansion unit is working. I downloaded the ever dependable Kermit and after stripping it somewhat to fit onto a 720k floppy loaded it up and dialled out to my BBS and sent off a couple of emails. It’s been interesting running a machine with no fixed disk. The second drive by the way has started working, maybe whatever was preventing it from reading disks before has been dislodged. I made a quick video of the 5140 below:-
I also found the following advert for the 5140 on Youtube, in it you can see the machine hooked up to a monitor, I lust after that monitor, I want one, a lot:-
I’ve taken a break from playing with the Samsung PenMaster and thought I’d take another crack at getting my IBM 5140 up and running. When I originally plugged it in, the power supply fizzled for a while and then went pop and as I have been unable to source a suitable replacement the machine has languished in storage since.
It occurred to me a few days ago as I was wiring the PenMaster up to the new bench top power supply I’d purchased that I could of course use it to power the 5140. The power connector for the IBM has a 5.5mm diameter plug with a 2.5mm centre. I checked online and confirmed that the centre pin is positive so I cut off the cable from the fried power supply, checked which wire was which with a meter and hooked it up to the bench top PS.
The 5140 requires 15v DC at 2.7 amps to both run and charge the battery at the same time. The battery looks as though it’s had a leak in the past so I’d already removed it but wasn’t sure if the 5140 would run with it disconnected. Fortunately it turns out that it does as on power up it POSTed and after querying both drives which were empty dropped into the default BASIC.
The unit came with a wallet containing PC DOS 3.30 on both 3.5 and 5.25″ disks so I restarted with the relevant disk in drive A and the machine booted successfully to DOS. Drive B is not currently working although I suspect it’s just a cleaning job.
Both drives are 720k units and pop up for access as you open the lid. Incidentally this was the first IBM machine to use 3.5″ drives, the first to run on batteries and the first to use surface mount technology. The 80×25 LCD screen on my example is unfortunately not backlit as found on later models and is almost identical to the one found on the Epson PX-16 and similarly lacking in contrast.
The CPU is an Intel 80C88 running at 4.77 MHz, there’s 512 KB of RAM and no HDD nor room for one. There is space inside for an optional modem although mine doesn’t have one and other expansion comes courtesy of units which have to be clipped on at the back.
I have two expansion units, one provides a serial and parallel port and the other is I believe for connecting a CRT. The existing LCD is removed by simply pushing the bottom of the square panel below it which tips forward and allows the screen to be lifted off, the idea being that the unit quickly converts from a portable to desktop.
Targets are to try to get the second drive working hopefully with a simple head clean and then to try out the expansion units by connecting a modem to the serial port, possibly a printer to the parallel port and then see if I can get a video signal from the other expansion unit.