Davide BucciI could save an #IBM model M #keyboard that was about to be sent to the e-waste. It is the dirtiest keyboard I have ever seen 😅 But it works and will be cleaned. It is in a good shape, too! #mechanicalkeyboard
I could also save the computer that went with the keyboard, an #IBM PS/2 model 30 with a screen that seems to be monochrome. I could not resist saving also a #SUN #SPARCstation 5, that I found there. I don’t know if they work, and they stayed one night under heavy rain. I will check them also to remove #batteries. #retrocomputing
Well, I could put together again the #IBM model M keyboard. Now it is very clean! I also got an USB to PS/2 converter and it works very well. I love the feeling when I am typing. Just one ALT keycap cover is missing. Love it! #mechanicalkeyboard #retrocomputing #IBMtypeM
I can now start trying to repair the #IBM PS/2 model 30 computer. After a deep clean and a global check, the computer starts, but both the disk drive and the hard drive do not work. The screen, a nice #IBM8503 002, does not work properly, neither: the vertical deflection is very distorted. #retrocomputing #IBMPS2 #repair
The screen is also horribly dirty. I opened it (after buying a set of long security Torx bits). Its electronic circuit is quite simple, as it’s a monochrome monitor, yet it is not very nice to work on: you have to disassemble almost everything to check components. I was suspicious of the capacitors and the TDA1170 that controls the vertical deflection. #repair #IBM #monitor
Ah, here’s the culprit! A 470uF capacitor in series with the deflection joke vertical coil reads about 1/10 of the rated capacitance. The TDA1170 is perfectly fine! That was an easy repair. #IBM #repair #retrocomputing #capacitor
Getting back to the #IBM PS/2 model 30 repair, I have some troubles with the Alps 720KB disk drive. I am trying to follow certain signals (the motor does not spin), but having a schematics would ease things a lot. #repair #PS2 #retrocomputing #retrorepair #floppy #alps
I continued the reverse engineering of the Alps floppy drive of the IBM PS/2 model 30. The stepper driver HA13421 has its power supply switched by a PNP transistor. Checking voltages, I found 2.2V, when the stepper was supposed to be active. This is not enough. I checked the two PNP transistors on the top, they form a current limiter set to 220 mA by R31, a 2.7Ω resistance that... was open! Now the heads move, but it is not enough to fix the drive. #repair #IBM #retrocomputing.
Incidentally, my #DIY ESR and capacitance meter can be used to measure a low resistance in AC with the 4-probe method and it is fairly accurate.
The original #IBM hard drive doesn’t work anymore (it seems it happens quite regularly) and the floppy disk drive is broken, too. I decided to add an XTIDE card that worked at the first attempt. Very cool little card!
Dune 2 works on the #IBM PS/2 model 30! It’s slow, but kind of playable. I still remember the introduction speech by heart, as it was one of the favourite games of my late father. #retrocomputing
I tested my games on the #IBM PS/2 Model 30. They work perfectly 🥰 #retrocomputing
Between 1996 and 1998, I wrote a complete management system for an Italian Fantasy football team. I wrote it from scratch for a friend who had an Olivetti M200, that was a slow computer for that time. I wrote it in #QuickBasic, with some assembly. It runs fine on the #IBM PS/2, even if it was written for a color monitor. It was pretty refined and even had a complete help system (ironically it was useful for me to remind how to use the software after almost 30 years) #retrocomputing
If you want to run it on DOSBox, or have a peek to the source code of my fantasy football management program, I put it here: http://davbucci.chez-alice.fr/index.php?argument=retroc/oldp/oldp.inc I used a technique to sort of include inline assembly that was quite elegant and that I learnt from a paper by Francesco Balena in the mid-1990's. #retrocomputing #retrocoding #BASIC #QuickBasic #Fantacalcio #MSDOS
I also decided to move Analysis in the page dedicated to my old programs. Analysis was a Windows 3.1 program I wrote between 1998-2002 and that could draw mathematical functions. It was mainly written in Visual Basic 3.0, with a DLL written in C that could parse functions: http://davbucci.chez-alice.fr/index.php?argument=retroc/oldp/oldp.inc
LFA 🇮🇨@davbucci Is the paper online by any chance?
@lfa Hi, I could not find it, unfortunately. There was a BASIC program that extracted the source from the comments, used the DEBUG command to compile it (!) and created a string in BASIC that contained the compiled routine. You then had to jump to the address of the string and Bob's your uncle! I found it was brilliant and effective! I don't remember if I read it on Computer Programming, or on Visual Basic Journal. Both were Italian magazines.
@davbucci Thanks for your reply. I assumed it would be written in Italian, but I can read Italian. Have a nice weekend and thank you very much :-)
@lfa I found this, maybe it is interesting for you: http://davbucci.chez-alice.fr/retroc/oldp/miniasm2.zip I'm not sure if it was an inline assembly. Maybe the source files were external. EDIT: yes, definitely, the tool requires an external file containing the routine, then generates the BASIC code with the asm.
Kcopy@davbucci Unfortunately, my IBM PS/2 model 30 8086 has the same problems. Floppy defective, HDD defective. HDD can be solved with XTIDE, but floppy is bad.
@Karre it looks many have issues with those floppy drives. My HD is dead, too, but I haven't checked if I can repair it yet. I should definitely explore options like XTIDE.
botvolution@davbucci
Is that a DIY capacitance tester?
Is that a DIY capacitance tester?
@botvolution yes, it can do in-circuit measurements, too. I use it quite frequently for repairing things. Capacitance measurements can not be precise when done in circuit, but it helps spotting strange things. https://github.com/DarwinNE/EsrMeter
Paul@davbucci miliFarads as a unit always throws me 😄
@forty2 it's because I have been lazy while writing the PIC asm code 🤪 https://github.com/DarwinNE/EsrMeter/blob/main/esr.asm
root42
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