🇺🇦 УМПК-Р (UMPK-R): Part 4 (Faulty DRAM?) [TCE #0581]
31Thanks to PCBWAY for their ongoing support! http://www.pcbway.com/
I've been thinking about this little machine a lot since Part 3, trying to figure out how to troubleshoot it (also reading & re-reading helpful comments by @sergijtolmeros and others!)
I've started translating the operation manual (thanks to Grok & ChatGPT) which has helped me to understand the machine a bit more. I'm thinking that four of the eight DRAM are possibly faulty, pulling those bits on the data bus high permanently. So I'll be looking at replacing those 32kbit КР565РУ5Д1 DRAM chips - well, replace one and see if that changes the data bus behaviour.
The manual, including my rough English translation, can be found here:
https://github.com/0ddjob/UMPK-R_Computer
00:00 ... Intro (Dec 2024)
03:30 ... Testing the video output stage (thanks to PCBWAY!)
04:50 ... Time to get started again (Mar 2025)
05:55 ... Major ICs on motherboard
07:30 ... Rambling about the DMA controller
10:50 ... Logic analyser time: ROM select at boot?
17:25 ... Data bus problems?
27:14 ... Channel thanks & outro
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From Part 3:
Just continuing on trying to get a video signal out of the machine, similar to the modern РАДИО-86РК implementation before I continue troubleshooting the rest of the machine (if required).
Sergey's excellent reproduction of the Radio 86RK:
https://github.com/skiselev/radio-86rk
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From Part 1:
Here we have another "serially produced" version of the Soviet-era home brew computer Радио-86РК (Radio-86RK) based on their Intel 8080A equivalent, the КР580ВМ80А (KR580VM80A). This fellow comes from Мукачево (Mukachevo) in the Ukrainian SSR (as far as I can tell). There was a 16KByte version (УМПК-Р16) and this 32KByte version (УМПК-Р32).
It is a pretty simple machine, nicely made if we ignore the membrane keyboard with a dozen space bars. It has a four-pin socket for power in, a 5-pin DIN for cassette, RF-output for TV and a DN4612-style expansion port (СНП?).
As it's an 8080-based machine it requires ±5VDC and +12VDC.
My understanding of the special keys on the JCUKEN keyboard layout (thanks to @Mercury13kiev & @sergijtolmeros for their input!):
[ВК] = Возврат Каретки = carriage return
[ЗБ] = ЗЗабой = backspace
[СС] = Специальные символы = special characters
[ПС] = Перевод Строки = line feed
[СБР] = Сброс = reset
[УС] = Управляющие символы = control characters
[АР2] = Автоматический Режим 2 (automatic mode), or more recently Альтернативный Регистр 2 (alternate register)
[СТР] = Система Трансформации Реальности, or [CTRL]
ВКЛ = Бключить (turn ON)
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