Альфа БК (Alpha BK): Part 2 (Troubleshooting Begins) [TCE #0450]

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The Clueless Engineer

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Published on May 18, 2024 10:41:13 AM ● Video Link: https://www.youtube.com/watch?v=khIJqGc9NvU

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Let's Play

Duration: 45:41

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26

We first looked at this machine about a year ago, way back in TCE #0297. I didn't have any 8080-related spare parts (such as the 8257 DMA controller or 8275 CRT controller) so assumed "can't fix it right now" ... basically, powered it on and got no video output ... "too hard" basket.

But I have those parts now so finally decided to have another crack at it.

I have done some troubleshooting - essentially, I'm still not getting any video output. However, it does seem that there is some output when I check on an oscilloscope ... but is it inverted compared to "normal" Western baseband analogue video signal ... ?

Connecting it up to the Eyoyoyoyoyoyo LCD display shows nothing ... it senses that there is some sort of signal ... the "no signal" message disappears ... but there's nothing there it recognises. Same result with the El Gato USB capture dongle.

I think I might check Sergey's re-implementation of the Radio 86RK for a hint, and perhaps also check the original documentation (see below).

From the Part 1 video description:
The Alpha BK is a mass produced version of the famous Радио 86РК (Radio 86RK), an Intel 8080 (clone) based home brew computer detailed in "Radio" magazine (in 1986):
https://en.wikipedia.org/wiki/Radio-86RK

Lots of info here - including a modern version of the original Radio 86RK design:
https://github.com/skiselev/radio-86rk

Information about the Alpha BK:
https://github.com/alemorf/retro_computers/tree/master/Alfa-BK

ОТКЛ (отключить): OFF
ВКЛ: ON
ВНЕШ УСТРОЙСТВА: EXTERNAL DEVICES
МФ: magnetophone, i.e. cassette recorder
ТВ: TV

Soviet parts used with Latin transliterations & equivalent Western part:
КР580ВВ55А (KR580VV55A): Intel 8255 programmable peripheral interface (PPI)
КР580ВГ75 (KR580VG75): Intel 8257 programmable DMA controller
КР580ВТ57 (KR580VT57): Intel 8275 CRT controller
КР580ВМ80А (KR580VM80A): Intel 8080A CPU
КР580ГФ24 (KR580GF24): Intel 8224 clock generator & driver
КС573РФ2 (KS573RF2): 2716 2KByte EPROM
КР565РУ5Д (KR565RU5D): 64Kbit DRAM (I think)
К589ИР12 (K589IR12): multimode buffer register
К155ИР1 (K155IR1): 7495 4-bit shift register
К155ИР13 (K155IR13): 74198 8-bit shift register
140УД608 (140UD608): op. amp.