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Robotrontechnik-Forum » Technische Diskussionen » Another ask for help with A5120 » Themenansicht

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000
04.04.2016, 20:55 Uhr
Bolverk

Hello!
At first, excuse me for using english language, I can barely understand german, so it's yet impossible for me to write in german.
I'm electronics engineer and in free time I love repairing old Soviet time digital electronics. About half year ago I found this A5120 computer moment before it was cut in pieces for precious metals. I always wanted true oldschool computer with green screen so I would very like to get this thing running again. It was located in wet basement for at least 10 years.
Components I have are:
K2526 CPU board
K3526.00 RAM
K7024 video controller
K8025 serial controller
K5120 floppy disk controller
3 pcs of K5600.10 floppy drives
K7222 display

First I checked all voltages - everything seems to be OK, all LEDs on lower board are lit. I read 2708 ROMs from video board, floppy controller and CPU board and tried to turn it on with cards inserted. Nothing was shown on screen. I measured that there are signals on video board output, but nothing was displayed. Long story shord, I had to rewind UHA78 secondary winding and repair one of primary windings too. And so now I have image - messy symbols on screen and floppy drive activity. As I understand that this is normal behavior of this computer as it should boot from floppy. So thereš my questions:
1. Should cards be in specific order?
2. I have serial keyboard with another Z80 CPU and 2716 ROM in it. As I understand that I might need parallel keyboard or maybe I need specifis sowtware to work with serial keyboard?
3. Operating system. Is it possible to ask You for floppy disk OS image that would work with my setup? DOS-like operating system would be great. I understand that I need specific floppies and drive that can write system tracks, but I think that I can get all of these.
4. Are there any programming languages available that would run on provided OS? I would really love to write some small software that runs on this computer. I'm not afraid of assembly, so I just need where to start. Once I made ISA card just for fun, and developing electronics is part of my job so after some time I could make card for Robotron too. But it's a long shot, computer are still not running.
5. ROMs. I converted Video board ROM contents into character set image (attached below) to see all symbols that are available. Problem is that it's cyrillic letters only. I would like to have latin letters better for my purposes. Does anyone of You have latin letter ROM images for my video board? Might there be any changes in CPU board ROM image too?
You can get all information I read from my ROMs here.

Dieser Beitrag wurde am 04.04.2016 um 21:15 Uhr von Bolverk editiert.

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001
04.04.2016, 23:38 Uhr
constanze czech

Hi!
Well done so far. Does the unit steps through the drives from down to top after starting? If all drives light up at the same moment and stay on, you have a failure.

The card order should be (from the drives to the crt):
RAM, Floppy, Serial adapter, CPU, graphics.

You say, you have a serial keyboard that came with the unit? It should be a K7637 with a 10-pin grey EFS-connector. This must be connected to the right bottom connector on the computer. Usually, you can use this keyboard or the big parallel one, connected to the 26pin connector directly on the cpu. The hardware-base is the same but older units don`t have a power button in the units socket but on top of the keyboard. On the back, a small black cable with another EFS-10 goes to the lowest connecor on the K8025. Directly connected to the K8025, the keyboard wont work due to missing signals and voltages.

The OS must be generated for your keyboard version and screen-type (K7221 with 64x16 or K7222 with 80x24 chars (you have the 2nd) but the remaining parts are mostly the same in most systems.

Where are you from, by the way? Russia? Perhaps you can help us in questions about ancient soviet computers.

If you give a email-adress, we can send you a 5,25" DD image from the program copyqm or teledisk. You will find these programms in the www for DOS-machines up to 80486.

For the A5120, there are about one dozend of operating systems (and even more versions) and a lot of languages: assembler, BASIC-interpreter, compiler, Fortran-77, C. I am pretty sure, there must be cobol and forth, too.

We are sorry for the documentation but we only have docs in german language. If you encounter some specific problem, just ask here and you`ll get help!

K5600.10 drives can cause a lot of problems from broken plastic parts to failing optical sensors to greasy mechanical parts. There are also some potis for adjustment. After checking the drives optically and for easy movement of the parts, you can try to boot the OS. If this works with even one drive, you then can start the computers test program "HARDY" and analyse the behavior of the drives such as failure-rate, correct speed, repositioning error and so on.

bye
Sebastian
--
biete 3-Raum-Computer 96m², Dusche, WC, Zentralheizung, Ferritkerngrill...(nicht ganz) ruhige Wohnlage....zum Zeitwert...

Dieser Beitrag wurde am 04.04.2016 um 23:46 Uhr von sebastian czech editiert.

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002
05.04.2016, 14:32 Uhr
holm

Avatar von holm

Hi Bolverk (Hu...Wall?).. please com into the another thread about the A5120 here.. the problems are very similar and you have made already a good job if you've repaired that ÜHA78 :-)

When no other jumps in having an link to the ROM images, I'll read out original the Character Generator ROMs from the K7024 for you, shouldn't be a problem.

There is no "DOS" for that Computer since it has no 8086 CPU, but there are several variants of CP/M
(CP/A, SCP,SCPX,MicroDos) for it, even a Zilog RIO Clone called UDOS.

Regards,

Holm
--
float R,y=1.5,x,r,A,P,B;int u,h=80,n=80,s;main(c,v)int c;char **v;
{s=(c>1?(h=atoi(v[1])):h)*h/2;for(R=6./h;s%h||(y-=R,x=-2),s;4<(P=B*B)+
(r=A*A)|++u==n&&putchar(*(((--s%h)?(u<n?--u%6:6):7)+"World! \n"))&&
(A=B=P=u=r=0,x+=R/2))A=B*2*A+y,B=P+x-r;}

Dieser Beitrag wurde am 05.04.2016 um 14:32 Uhr von holm editiert.

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003
05.04.2016, 15:04 Uhr
constanze czech

The internal black cable belongs to the 2nd port on the K8025, not the lowest. My fault.
--
biete 3-Raum-Computer 96m², Dusche, WC, Zentralheizung, Ferritkerngrill...(nicht ganz) ruhige Wohnlage....zum Zeitwert...

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004
05.04.2016, 23:07 Uhr
Bolverk

Thank You for fast and detailed answers!
No, I'm not from Russia, I'm from post-Soviet country Latvia. Even after 25 years after Soviet time there can be found interesting things from past like this computer. I'm not computer collector but I know two local collectors, one of who are old man with great collection of personal computers, another are my friend with good collection too. Local university has its own collection with really old computers, but their collecion are not freely available. But if You are interested in any parts from Soviet made electronics or information about them, feel free to ask me in private, I will help if it will be possible. Another cool Sovet computer I have is Iskra-226 with 8 inch drives and magnetic tape loader.
--
OK, my updates about my A5120. First thing I have done following Sebastians suggestion - I rearranged cards in correct order and tried to turn it on. After second there are three or four flashes on floppy drive LEDs - some times all drives flashes, some time only lowest one. Then all three drives turns LEDs and spins disk. That's it, it does not time out. So I think that there are failure. What's first thing to search for it? One time with floppy installed it stopped bothdrives with no floppies, and showed only ";" symbols on screen. If it helps, I can make video of it trying to start.
Following suggestions on other A5120 thread I checked both loops between A10/C10 and A27/C27. 27 seems to be OK - turned off computer shows 0Ohm between A27/C27 of all cards and turned on shows 0V. 10 seems to have problem, because floppy, serial and CPU does not show 0Ohm and turned on computer shows 4,3V on floppy and CPU board and under 1V on serial board so these boards interrupts this loop. Could this be any problem?
Keyboard I have is marked as K7637 on its PCB. Thank You for connection description, I'll connect it properly. I downloaded Teledisk software, You can send me OS image to obalins@gmail.com. Next I have to find proper floppy and drive.

Holm I would very appreciate if You could help me with latin character ROMs. Maybe it's possible to ask for CPU board ROM image too? I would like to compare it with mine. Maybe mine CPU ROM are modified, because there's something written by hand over original sticker.
About OSes - when I manage to write image to floppy and boot computer with any of OSes, then I could start to choose between these You mentioned. It's a long way to go.

Dieser Beitrag wurde am 06.04.2016 um 08:39 Uhr von Bolverk editiert.

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005
06.04.2016, 22:58 Uhr
Bolverk

Thank You for ROM images Rudiger and wpwsaw! Converted latin video ROM contents to image, looks good! I'll try to program these in 28C16 (I can only read 2708) and see if at least symbol problem will be done.

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006
07.04.2016, 09:13 Uhr
constanze czech

If the screen shows just one character in every position during startup, I think, you are dealing with a broken ABS (grafics) board or a broken OPS (RAM). Both are nowadays not that rarely cause of failure.

I suppose, the installed boards are the only K1520 board in you location, right?

You can try to start the computer without the memory card. It then should do nothing on the drives but we perhaps could eliminate a failure from this card. The upper 2kb of the 64k RAM are in parallel with the 2kb screnn character RAM on the ABS card. If you get a nice mix of everything on the screen, it could be a sign for broken RAM. But somebody here has written a RAM-TEST programm for the EPROM on the A5120s CPU board. This could help you to find the broken IC.

Very common are also failures in the data and adress line drivers on the boards, especially the russian versions as the K589UP12 (DS8212) and the K589An16 (DS8216). Check them outside the computer with a scope for working outputs within a valid logic rage (0-1.2 and 2.4 to 5). Perhaps one of them (also on other boards) blocks the data lines of the bus.

You have the stadard serial keyboard. If the missing caps are gone, we will find a way to send you a replacement.

If you are not scared for the costs, we of course can use the way, HOLM help the man from Italy and you can send your cards or perhaps the cards and 1 drive to us for checking in our machine.

schematics for the boards are here: http://9hal.ath.cx/usr/digital-ag/archiv/#Schaltpl%C3%A4ne
--
biete 3-Raum-Computer 96m², Dusche, WC, Zentralheizung, Ferritkerngrill...(nicht ganz) ruhige Wohnlage....zum Zeitwert...

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007
07.04.2016, 11:21 Uhr
Bolverk

Oh, that link is really, really great. I'm wery thankful for that. There are even CM5300 schematics that can't be found on russian sites.

Yes, I read that Holm helped to repair another A5120, but I think that I'll repair my computer by myself. To make things work, that's one of most interesting things to do. Now following Your suggestions and schematics I'll check those weak points and report any progress when I'll found out anything.

RAM test CPU ROM image would be great too, if I'm not asking too much.

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008
07.04.2016, 12:27 Uhr
holm

Avatar von holm

The Problem with the A5120 and related computers is that you wouldn't see anything on the screen until it is fully working. Without a working system for testing purposes ot a 2nd card set this is a pain in the ass to repair it.

Send me your mail address with a P/N, I'll send you the RAM-Test Image from ambrosius (that's the mentioned file you are looking for).

Regards,

Holm
--
float R,y=1.5,x,r,A,P,B;int u,h=80,n=80,s;main(c,v)int c;char **v;
{s=(c>1?(h=atoi(v[1])):h)*h/2;for(R=6./h;s%h||(y-=R,x=-2),s;4<(P=B*B)+
(r=A*A)|++u==n&&putchar(*(((--s%h)?(u<n?--u%6:6):7)+"World! \n"))&&
(A=B=P=u=r=0,x+=R/2))A=B*2*A+y,B=P+x-r;}

Dieser Beitrag wurde am 07.04.2016 um 12:29 Uhr von holm editiert.

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009
07.04.2016, 21:59 Uhr
Bolverk

I have some progress. Holm sent me RAMtest and I burned it into 28C16. I made adaptor to fit it in place of 2708 and turned on computer. And it seems that RAM test runs good! Also I found out that screen is slightly shifted left so I don't see first eight characters, but now I have schematics and I think that I'll figure out how to get it in place.
Is that OK that when RAM test runs, there are some floppy drive activity - LEDs are lit for a bit and drives are making silent noise?
And one more time thank You all for helping me with this machine!

Dieser Beitrag wurde am 07.04.2016 um 22:41 Uhr von Bolverk editiert.

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