Sorry to bump in so late, but a response is better that none.

lausvi wrote on 2019-09-14, 16:34:

Also I would like to add some more RAM to the machine (it currently has only the built-in 2MB). I've read that these are somewhat special, but will any IBM PS/2 -titled RAM work, I believe it should take 2, 4 or 8 MB ones (not 2x4MB I have read)?

Sadly, no. IBM PS/2 RAM had special presence detection codes for various models. The L40 is somewhat unique. There is a topic discussing RAM here. Also check out Ardent Tool's page on this https://ardent-tool.com/memory/Identification.html

There are some unique FRU parts for the RAM including the fabled FRU 79F1004 8MB SIMM. These are unfindable nowadays and I wouldn't bother looking for them. Some modifications can be done to industry standard SIMM's that have 4 jumper bridges on the side. Note that the L40SX is VERY picky on its RAM timing and ranks.

lausvi wrote on 2019-09-14, 16:34:

I am also thinking of rebuilding the NiCd main battery, we'll see about that. It is a lovely little machine and especially the keyboard is just great to type on.

As far as the battery goes, its very simple in design. The battery is 8.5V and max 12.6V which happens to coincide with the voltage of 3 lithium cells in series. It will attempt to charge the battery and cut off based on the original NiCD's thermsistor. Within a range of 4 kilohms to 30 kilohms. Using lithium cells I recommend building a BMS or charge the cells externally.

I have the external numpad too but haven't figured out the pinout yet. I see what I can do.

Thanks!

Ah, it appears I forgot to update on my progress here (I posted on several forums about the cable pinout). I eventually solved all the issues I had.

I friendly Redditor sent me a pinout for the external numpad cable and I posted it on reddit: https://www.reddit.com/r/retrobattlestations/ … web2x&context=3

I also managed to add some extra RAM. I bought an IBM 71F7010 (4MB) stick from eBay and set the ID jumpers (surface mount 0-ohm resistors) according to the instrucions on here: http://www.mcamafia.de/mcapage0/memory01.htm and it worked! I needed to trim the socket somewhat (as explained on the site linked). I now have 2MB on the motherboard + 4MB making it 6MB total. Not much but still triple of what I had before!

I replaced the NiCds in the battery case with new ones and the pack works ok, just need to remember to charge the pack regularily to keep the NiCds happy. I can now operate the machine on battery (haven't really measured how long, the manual states 3 hours which might be a bit much, then again I have added a math co-processor and the RAM, then again there is no spinning hard drive....).

While working on the RAM, I noticed that there were some capacitors on the mainboard that had clearly started leaking. So I had to do a full recap as well. I used tantalums on several places as I couldn't get low-profile electrolytics (like the orignals) and there was number of spots where height was limited due to the packed nature of the laptop.

Lot's of work but it is a lovely machine and perhaps mine is now mostly done for a moment!

Thats really awesome to hear! Pretty cool you got so far with it!

I remember the weird green Nichicon caps, very strange small design for that capacitance. I had an L40SX before which had the same one's and I attempted to desolder them in an effort to replace them, but its risky business. I got a second L40SX as a gift from someone for parts, and the motherboard still works thankfully. There are some L40 boards out there that uses SMD caps which are alot easier to get ahold of. Keep that in mind if you're hunting for a new mainboard. I am relieved that tantalum ones work fine too, I should have done the same if I could rewind time 😀

Hope its still a fun project all these days later, its a pretty dull office laptop but for some reason still interesting. I go hack together a Covox speech thing DAC for the parallel port to see if I can get sound out of it. I also highly recommend messing around with RS-232, as a terminal to a modern PC or as a PPP gateway to internet on the L40. Cheers

Thanks!

I tried a Covox clone on my L40, too! At the moment it was the easiest machine with a parallel port to dig up! Works, but had to keep the sample rate pretty low.

I also have a RS232 Wifi modem, which I quickly tested in Windows 3.1's Terminal, cool stuff! With baud rates low enough, the ghosting of the LCD doesn't show up! 😁

Hello! I have a similar laptop L40SX. 4 mb RAM and 128 mb cf card. Everything works but I can not connect a ps/2 mouse in any way. Drivers in MSdos 6.22 (mouse.exe , mouse.com, a4mouse5.com, gmouse.exe) do not seem to see that a mouse is connected to the port. Error "no mouse found", "cannot find pointer device" At the same time, the red LED on the mouse is on. In the settings of reference disk, I did not find any settings related to ps/2 . Tried different mouse: sven base 305 combo, genius netscroll 130, microsoft optical mouse. Already starting to worry that the port of the laptop is fault. Please help in troubleshooting.