Peter's site blog

Please read ! 
If NO IMAGES will be shown, use instead of


I have prepared a new blog with wordpress at !!!

Thank you.
Got an IBM Portable PC 5155. Really slow, but it's a nice engineering piece. 
Sunday, April 23, 2017, 09:00 PM
Posted by Administrator
This Portable PC is heavy, but it's an IBM PC/XT in a case with a build in amber CRT screen.
It's factory configuration only includes 256KB RAM, an IBM PC floppy controller and a CGA graphics card. The internal screen is feed by an FBAS (Composite) video signal (and not with 9-pin connector).

An original 64-256KB memory card was installed, which results in 512KB in total.
But I managed to add interface cards, and I replaced the original memory card with a Mycomp MEMS memory card, which can be populated with gigantic 2048KB RAM, and this card can offer conventional *and* expanded memory (at the same time).
In the screenshot, you can see the result after it was booted (IBM DOS 5.02 is used).

Believe me, repairing or just changing the cards, DIP switches or memory chips on the mainboard is *NO* fun. Inside the case it's really (over)crowded. But on the other side, in terms of mechanical quality, this PC seems to be very good quality.

Take a look at the 'related link' below, if you are interested in further details.
add comment ( 179 views )   |  permalink   |  related link   |   ( 3 / 1956 )
Amstrad PC1640 on steroids ? Not really, but still a surprise... 
Monday, March 13, 2017, 12:30 AM
Posted by Administrator
Recently I got some problems related with an Amstrad PC1640, the floppy drive was not working properly (formatting and read errors, also when reading disks, formatted on the Amstrad, but on a different PC). So I decided to replace the floppy drive, which is in fact a very unusual, belt driven OEM Alps drive (DFD222A01, Amstrad part no 40046).
The first surprise while opening the PC1640 - I discovered a small additional pcb which was connected with many cables to the area on the mainboard the crystal is located.
There was also a 3-way switch to change the frequency from 4 MHz to ~10 Mhz.
The additonal board and the switch is marked green in the picture below.

Also, I discovered (never used it) an Intel 8087 (marked light blue in the picture) !
This might be useful when using one of the first AUTOCAD versions.

Regarding my wish to replace the floppy drive - this was a desaster. I was reading >John Elliott's Amstrad hardware compatibility page< and hoped that my TEAC FD-54B can replace the original drive.

But you can't replace that floppy drive for two reasons:
a) the metal cage for the floppy drive does not have the correct "holes" at rear...
b) even if you take a saw and make the holes bigger, the new floppy drive still does NOT work

I know the jumper settings has to be changed from (IBM PC compatible) DS1 to DS0 (because of the twisted cables of the IBM PC), but the Amstrad ALWAYS SAYS the floppy controller has problems with the drive. Also, the motor light was always on, which points to DRIVE SELECT problems. But DS1 doesn't work too.
Also, rotating the cable connector ends up also in drive light always on problems but the floppy controller do not show up the error message.
So I decided to check again the original Amstrad floppy drive, turning the motor (with the belt), and also checked the drive head movement. I didn't recognized any problem, so I exchanged the non-working TEAC FD-54B with the Alps OEM drive (the Amstrad one) back.
After reassembling, it suddenly worked without errors. Strange.
add comment ( 187 views )   |  permalink   |  related link   |   ( 3 / 1909 )
Transferring binary files to a DOS PC without anything else but DOS ? 
Monday, February 27, 2017, 08:02 PM
Posted by Administrator
I've a Toshiba T5200 laptop, which has a working harddrive with an installed DOS but a faulty floppy disk drive. There is a way to connect a floppy drive to a parallel port by using the correct adapter, but I do not own this adapter.
So I thought it must be an other way existing to transfer files, like using MS-DOS KERMIT.
Unfortunately transferring binary files over a cross-over cable without any file protocol is NOT possible because of non ASCII characters with a special meaning.
If there is nothing else but DOS existing, you can use MODE COM1 and CTTY at least.
MODE COM1 with additional parameters like the BAUD rate sets the serial port.
CTTY COM1 will redirect the command line to the serial port then.
But how to convert the binary file(s) to an easily approach without any effort for me ?
I remembered DEBUG - you can type in the data of a binary file just by using the 'e' command, and then set then name with the 'n' command. Also, you have to set the file size of it by using the CX register.
I wrote a small C program to accomplish this mission, the program just converts any file smaller than 64KB to a text file, which can be used for a recreation of a binary file just by redirecting the generated text file as input for the DEBUG command.

(btw. redirection does not work with DOSBOX, but on every real or virtual PC with an installed DOS)

Feel free to download the binary and the source of the file by clicking on "related link".

P.S.: You can even print the text file to paper, so you will be able to get it up and running even if all transfer options are gone or if all floppy disks of the world will fail ;-)
add comment ( 166 views )   |  permalink   |  related link   |   ( 3 / 1982 )
What to do if Floppy Drives don't read floppy disks ... 
Friday, January 6, 2017, 04:00 PM
Posted by Administrator
Sometimes you can't read floppy disks in your computer's floppy drive.
It can be related with the floppy disk media itself.
But the drive can be misaligned or faulty, too.
If you suspect the drive to be defect, you can replace it (if the drive is still available or can be taken out from an other (old) computer).
You can try to clean the r/w heads with special cleaning diskettes, or may be with cotton buds and pure alcohol. But this helps only in rare cases.

At least you should narrow down what is not working, and if it helps, do something (see below).

So there is a checklist I created:
a) Do your drive have a "belt" instead of a more modern direct drive ?
b) If so (with belt), check the belt. Does it have still a tension ?

c) if you want to use the drive and it has all power connectors correctly connected, does the LED light up if you try to access the drive (regardless of successfully reading a floppy) ?
d) if the LED does not give any sign, are you sure you connected the data line correctly (beware of the old IBM PC drive select crossover cables) ?
e) if the LED lights up but you can't read any sector, did you tried a different floppy disk or may be also a different data cable ?
f) if the LED lights up during access but even with different floppy medias reading doesn't work, did you try to format (if you can boot up with a different drive) a floppy with that problematic drive ?
g) if formatting a floppy media works, but you can't read this formatted floppy disk on other computers, did you're using the right media (DD versus HD floppy disks) ?
h) is the formatted floppy readable but only in the same drive ?

If yes is the answer for a), but b) can be answered with no, replace the belt with a similar, but new belt.

For drives without belt or with a belt with enough tension:
If you answer c) and d) with yes, continue with the subsequent points e) to h), otherwise you are lost and have to replace the drive.
If f) was successful, but g) and h) was answered with yes, you can try to re-align the drive, it sounds that the drive is misaligned. Just take another already formatted and proofed to be good floppy disk, insert this floppy disk, and try to change the position of the r/w head of the floppy very CAREFULLY. During this procedure, try to read the disk continuosly.
For 3.5" inch floppy disk drives, this will work sooner or later, I've successfully resurrected such drives a few times already.

The shown TEAC 3.5" floppy drive is an exception, because the logic board, see red arrows, is already also a mount for the drive head mechanics.

Another example is this drive from Sony, MPF72C-1, used for Thinkpads as an internal drive:

To move the head, just untighten CAREFULLY the one torx screw which holds the plastic head frame. If you move the head, do it in very small steps. One millimeter is very much.

Real "alignment floppy disks" are to be used with additional eletronic equipment like oscilloscopes. You will not have success just with such a media only.

If you're curious what possibilities exists for reading floppy drives, visit the excellent page from, see "related link" below. Try also >Herb's Floppy Drive info collection<.
add comment ( 185 views )   |  permalink   |  related link   |   ( 3 / 1973 )
It's a real nice (but heavy) "portable", the IBM PS/2 P70 - build 1989 'til 1991 
Sunday, October 30, 2016, 02:03 PM
Posted by Administrator
A real beauty, this IBM PS/2 P70 - a 386 based machine with an ESDI harddrive.

But also a delicate device, because meanwhile the floppy drive often could make problems (can be related with capacitors on the floppy drive board) and also the ESDI drive is NOT unproblematic. If you run SCANDISK (from MS-DOS 6 or later), and if you get after each program run loop more and more bad clusters, you have "disk snow". This means your drive is dying slowly. Also, trying to low level these ESDI drives is NOT easy, you should NOT use drive manager software for this task. There is a special setup floppy disk for this purpose, and there is a secret key for entering the low level format menu (press Ctrl-A within the normal diagnose main menu). But even then it could fail (this happened for my try). Can be related with the "bad sector table" which should be existing for each ESDI drive. Don't know an other reason, because otherwise if the drive controller is faulty, I would get errors while loading/saving files. But all things saved on hard drive works smoothly (no errors). Regardless of that, also the display can make problems.
The plasma display is - if it works - not too bad, see the second picture driving "Pole Position II"...

Last but not least the keyboard is excellent, similar to the famous "clicky" IBM PS/2 keyboards for the IBM desktop computers (but a bit more compact).

See "related link" for a related site / a source for the setup & diagnose disk for the P70.

add comment ( 205 views )   |  permalink   |  related link   |   ( 3 / 1943 )

<<First <Back | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | Next> Last>>