000
08.01.2026, 11:24 Uhr
RetroNora
|
Hello!
I think my A5120 is straight out hell and that the machine hates me.
I got A5120 with such configuration:
-serial keyboard (K7637.50),
- three K5601 drives (Teac FD55-FV-03-U),
- K7222.13 monitor(80x24).
The cards inside are:
-062-8471,
-062-8110,
-062-8440,
-012-6820,
-062-8390,
-062-8600.
When I powered on the system it was doing one of three things:
Option 1: it would not boot from any diskette drive, in fact all the floppy control bus was a big mess, it would try to read and write the floppy at the same time, /ST and /SD signals were too fast (of too high frequency) to be correct for TEAC floppy drives.
Option 2: It would clear the screen, write
ROBOTRON LOADER
SCPX 1526 - v 1.5 (52k)
B?
(I was booting from drive B and '?' was printed becasue I have polish chargen in my A5120 and I bet '?' have the same scancode as '>' in international/german chargen.
But it wouldn't stop to read the floppy and the system was frozen.
Option 3:
It would read the floppy, print the Robotron Loader... to the screen and would accept keyboard input, but it was messy. For example 'q' would end as 'a', 'z' as 'j' ect. I was not able to dir the floppy since none of the keys would make 'r'.
I think it is not due to chargens incompatibility since it would print 'ROBOTRON LOADER' fine, and looking at the keyboard manual, latin letters make the same scancodes across different national keyboard versions.
While looking for the issue that seemed to be random I have tried to test the 1K SRAM (2102) from ZVE board.
Arduino-based tester I found online said it was defective. But after I have socketed the IC my A5120 became even more broken.
I have checked all the obvious like bad/ shorted traces around SRAM Ic but it all seems fine.
The system behaves the same with or without the SRAM IC. I have also tried other with no effect.
Now the symptoms are:
- it is not trying to access any of the floppy drives,
- it is not able to run RAM test, instead it is displaying:
- with normal Boot ROM it is displaying random characters but these are not the random characters it would display at normal operation:
Does anyone have any idea what's going on? Why the keyboard input was scrambled? And if any issues with the ZVE SRAM ( I have read that it is used for resources protection under operating system) can result in such issue?
Greetings |
