So I've finally got this Soviet 'Microtrainer' МТ1804 up and running, but I'm experiencing problems with the execution of the example programs. Basically the memory seems to be working fine - I can assign values to memory locations using the front switches and they stay put. I can also assign values to registers programmatically, and I can see the results on the LEDs marked "microcommand/микрокоманда" when I run those lines of instructions. However, all other instructions I have tried seem to return a zero value (the LEDs show nothing). This is true for rotate, increment and add, as per the sample programs, and the commentaries on the programs suggest (and in one case explicitly states) you should be able to see the results right away on the LEDs.
As far as I can see there are two possible explanations, there may be more.
1) I've assumed that the LEDs in question will show me the results of operations, when in fact they only show me when values are being initially assigned to registers. However the commentary on the rotation programme specifically says that you will see the results of the rotation on the LEDs, and I don't see that.
2) There is something wrong with the "arithmetic-logical unit" (ie the CPU?) or with something downstream of it.
If 2 is the case, I'm wondering why I can assign values to registers, or is that a different kind of operation, not involving the "arithmetic-logical unit"?
As I understand it, the chip in question is based on the AM2900 from AMD,and the Microtrainer is functionally identical to the AM 2900 Learning and Evaluation Kit.
I wonder if people with more experience on or knowledge of this or similar machines might be able to advise as to what the likely problem is.