Synthezisers & retro computing

Saturday July 08, 2023

Cloning a disk from a TP380 to run on a TP365xd with no functioning FD or HDD


Friday July 15, 2022

Finalization of the unsupported cpu upgrade

I finally got some spare time to sit down with this project again, trying to fit a Kingston SX Now! (the LCM version that is tailored for the IBM PS/2 model 50z and 50z only...) with some will (and mild violence ;)) to fit my PS/2 model 30/286. The page over at Ardent-tools said that this was not really possible as the CMOS-chip would get in the way.

Well, as the proper LEM version was impossible to source anywhere (but i got lucky to find an LCM version) i decided to have a go at it. My basic goal was to get the CPU upgrade working while being able to revert back 100% to the original specification without physical damage of any kind.

Looking at the original configuration (with the 80287XL math coprocessor that i installed one year ago), i learned a while back that the CPU expansion would simply not fit as-is, and from Ardent-tools i also learned that the math co-pro needed to go (not compatible with the Kingston upgrade. Logically as well as physically). The Kingston expansion, when you try to fit it, will basically not go into the PLCC socket due to the CMOS chip being in the way. There is no way around that usually...


Which means that the CMOS chip needs to be re-located somewhere else (i use a Glitch Works GW-12887-1 replacement which was the only one i tried that actually worked in the 30/286. It can be bought over at and cost at the moment ~25USD. First i detached the chip from the planar and put it into a spare socket...


Next step was to find a way to re-route the signals using wires so that i could move the CMOS out of the way. For this i used Arduino jumper wires (these: that i cut the connectors from (20 cm cables sold in packs of 40 all over the web).


Next i got hold of a new 40-pin socket (available at basically any electronics shop) to which i soldered the cables according to the pins of the Glitch Works CMOS replacment. For each pin soldered, it was also covered in shrink-tubing to ensure that nothing got short-circuited.


Testing the fit and feasibility of how it all would be making it when the CPU expansion eventually will go on top. Thankfully it looked alright, but a tight squeeze for sure (not joking. Every millimeter counts in this case).


With everything connected to the original socket, i took the cheap exit and enclosed the CMOS in some antistatic bag and taped it down (using vinyl electric tape) to an unused spot in front of the planar. The CPU board did fit in the end (it was truly a quite tight squeeze) and for good measure, I isolated the CMOS socket from the board with proper non-conductive tape.


The computer started up (big relief from yours truly :)) but it did not yet perform as expected, it was more like the original 10MHZ 286 that was there originally. Some more digging on the Ardent-tools page and i found the cache-enabling program for the Kingston (very tiny utility that is around 3KB in size and does not consume RAM after execution).


With the Kingston utility started, it now detects the proper performance and this machine finally "flies" (relatively speaking).


Of course, the question everyone is asking... Yes, it runs Doom.;). Not without lag (mind you) but it runs. Unfortunately, as i only have the small monochrome monitor (i guess the game was not intended for this monitor, LOL), it IS a little bit difficult to see all the nuances ;)


Was it worth it? Well, yes and no. It took some time to re-arrange things to make them fit properly. 

Does it perform better? Yes it does, but it all depends on your application for sure. For gaming (even games that requires 386) it will be a hit-and-miss as many of the major titles till struggle dearly with a 386SX processor (perhaps even more so with the 16-bit bus that the 30/286 provides). But for more CPU-bound tasks, the difference is quite noticeable (Turbo Pascal now starts lightning fast for example, and many utilities run quite much faster).

While i might restore this unit to its former glory in the future, it has been a nice experience in total. Unless i stumble across some 286>486 expansion that is ;)

Tuesday February 15, 2022

IBM PS/2 model 30-286 CPU upgrade using unsupported option ;)

Recently i got hold of this CPU upgrade card, a Kingston SX/25-LCM, basically targeted at the IBM PS/2 model 50z (286) workstation. It was more or less purchased by mistake as it wouldn't (supposedly) fit my model 30-286 computer (as the Dallas chip would block proper insertion of this card). Some people also told me that the card would be to wide to fit inside the enclosure itself.

Shown here is the CPU upgrade card at the bottom and the motherboard (model 30-286) in the top. Notice the current 10Mhz 286 cpu right above the "Dallas" cmos chip (which in my case died on me and so i replaced it with a nicely working Tindie GW-12887-1 replacement that you can find here: gw-12887-1).

While doing some simulated "fitting in place", you can clearly notice how the Dallas-chip blocks proper insertion of the CPU board.

So how to deal with this? The option that i'm going to try out is to simply re-locate the Dallas chip completely at some other (not yet decided) place inside the enclosure. That would free up some space, hopefully enough to be able to fit this thing into this computer. Stay tuned for the full update regarding this ... :)

Friday December 10, 2021

Thinkpad 760 - replacing the CMOS battery

Yesterday i went about replacing the long since dead CMOS battery in the 760. At the same time, i checked the other battery (three cell) to the right and luckily enough it had not started to leak (yet. But it will be removed in the next few days as well. Havent decided yet if i will replace that one with a new as i relatively rarely use this machine for any serious business and so the functionality brought by the three-cell might be redundant).

To get access to the CMOS, you basically have to open the keyboard (flip it open). Underneath it, you have 4+6 screws near the front which you have to remove. After doing that, the palmrest (containing the speakers) can be snapped loose. Inside, you have to undo two more screws in order to access the left speaker cage, underneath which the old CMOS resides. Unplug it carefully.

Naturally, finding a 1:1 match of CMOS battery can be a challenge. If you do find one, they are severely overpriced in places like Ebay, etc. If you want to do this on a budget, then you should browse around for a regular CR2020 (or similar) where the connector does not really matter as we will do some surgery on it anyway, reusing the original one. In my case, i could source a 3volt, 150mah battery locally (for a newer generation Thinkpad) but where the connector was way to small.

Here you can see the original battery (yellow) compared to its much younger replacement. Notice the difference in connectors..


cut the original battery wires as close as possible to the battery itself. For the replacement battery, but its wires as close to the connector itself (go gain the maximum amount of wiring available to you). Its also good to have some correct sized shrink-tubing available (but lacking that, electrical/insulating tape will do).


Wire the corresponding cables up: black/black and red/red, solder them carefully (don't forget to put the shrink-tube on each cable before you solder them together) and finally slide the shring-tubes and heat them a bit so that they fit snugly against the cable, covering the solder spot underneath.


Plug the battery in, place the battery on its intended spot next to the left speaker-cage and put the PCB in place again with its two screws. Put the palmrest back and restore the screws on the backside of the keyboard.

Moment of truth. First reboot will probably give you a 201 still (because you have to properly set the date and time. And this time the machine will remember the values ;)). Reboot. Done! :)

Friday December 03, 2021

Revival of a 365E floppy drive unit - Part 1

About 2 year ago while i was trying to replace the belt on the Thinkpad 365E slim floppy unit (IBM calls them FRU 41H8387/41H7444 depending on if they are internal or external in a case) i unfortunately snapped one of the read-heads off (due to temporary "sausage fingers" :) ). I immediately started to search for the various FRUs given by this page:

ThinkWiki floppy connector guide

but failed miserably to source a replacement unit (they are rarer than hens teeth).

Fast forward to the current time and i took a closer look on the drive and i noticed the Mitsumi stamp on it - the unit is actually manufactured by Mitsumi and (in the IBM shroud) the model is called "D353FE2". Googling for that comes up with nothing, but lo and behold, apparently Mitsumi has a model just called "D353F2" (googling for this will give quite many hits).

What the Mitsumi original unit looks like:

And here is what the IBM branded unit looks like:

Naturally, IBM did not seem to just use a bog standard Mitsumi unit because in the IBM branded version, the connector is of the protruding kind with pins (which then "snapped" to the laptop) while the standard unit has this flat-cable connector.

Internally, the connector is stuck to this small control-board and i suspected that it might be worthwhile to source a standard Mitsumi D353F2 unit and then swap these boards between them? Would it work? What did i have to loose (you guessed right. Nothing :))

So i got to work, effectively swapping out the guts of the Mitsumi unit, putting the IBM unit contents in there

PCB with Protruding connector is IBM, the other is Mitsumi.

and i tried it out. No dice. I could hear the drive ticking inside the machine, but it surely was not reading any disks. Time for step two - the drive belt.

I measured the old belt using my digital caliper and found that it was 1.45mm wide, 0.48mm thick and ~22.4cm long. Taking into account that it most probably had stretched during its life (and dried out quite a bit), i assumed that the correct specs would be:

1.5mm wide, 0.5mm thick and 22cm length

and so i found a nice shop on Ebay who had one that could fit according to the potential measurements (sold as new for a Matsushita EME-279TC unit). I got the small package home and took the drive apart again, mounting the new belt. Time for the grand finale. Would it work? I grabbed one of my floppies off the shelf and tried to format it - it gave me a message that track 0 was bad. Bummer. I then used an unused floppy and retried it and this time it actually formatted the whole thing properly. YES!!

Now i was able to create files and reading them back worked. One odd thing that i noticed was that the newly formatted floppy reported back 1,1MB available (where it should really be closer to 1,4). I then took this same floppy and used it on another machine and to my dismay i saw that the new machine could not actually see my newly created text-file (from the 365E). Bummer again. I then wrote another textfile to the floppy and tried to read it on the 365E but the machine could only see the actual file that itself created in the first step. This probably means that the read-heads are out of alignment...

But those trials and tribulations will probably be in the next post here ;)

Wednesday November 24, 2021

Thinkpad 760E - sorting out cmos and dead hard-drive

Thinkpad 760E 

 So, today i recieved a Thinkpad model 760E that i bought from Ebay (to complete my collection of Thinkpads ranging from the 360 series up to the T590). It was bought as a spares machine with a suspected memory error so i was bracing for the worst (to sling the soldering-skills worst case).

When it turned up, i was quite surprised to see that it was in quite decent shape. Sure, it was a bit "sticky" (or "gooey") as the older members the thinkpad family tends to be (even rubbing off some black coating on my fingers when handling it in certain ways). After wiping it down some (there were some hairs stuck to the surface & old grime) i decided to boot it up. Initially i saw the memory error (I9990305 actually) and the "301" error code displaying on the screen (301 being most probably the cmos-battery which is not uncommon in these old fighters...). I also heard a number of "siren" like sounds coming out of the machine, while also seeing that the HDD symbol on the small screen just above the keyboard showed me the HDD symbol. I figured that the HDD was "kaputt" (and it surely was to say the least).

Trying to get into the machine (by pulling the two levers on each side of the keyboard backwards in order to get to the CD-rom unit, the battery and the hard-drive (because pulling them towards you will open the lid on the machine and make it ready for use;) i noticed that i could only pull the left-most lever, thus only lifting that side of the keyboard. After scratching my hair for a while, i decided to flip the machine over and open the small hatch that contains the memory PCB (a proprietary board with 2 dimm slots on it). After pulling this PCB away from the machine, i noticed that i could pull the right-most lever and finally could access the innards of this machine.

I pulled the HDD caddy and saw that it had two screws attached to it. After undoing them (and loosening the tape surrounding the caddy) i could carefully widen the plastic caddy around the drive that was contained inside, while carefully pulling the drive up, and it soon got free from its coffin ;)

 Freedom at last!!!

Next up will be to replace this dead HDD (it just emitted weird noises) with a 2.5 DOM-module that i have laying around here (1GB). But before i make that happen, i need to wait for a 44-pin male-male adapter that is ordered (to make the whole contraption fit inside the caddy).

To be continued..... 

Welcome to my new blog

The idea behind this place is to talk about some of the things that makes me tick:

Synthesizers (old and new) as well as retro computers (pre 1995 mainly).

Here you will see (and hopefully chip in) my trials and tribulations around using and fixing up old hardware (from retro-fitting old synthesizers with midi to upgrading old laptops, fixing old floppy drives, etc)

Here is my favourite room :)

where i do various things such as...

Stay tuned. 

Update soon....