Альфа БК (Alpha BK): Part 4 (Making Progress) [TCE #0454]

Channel:

The Clueless Engineer

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Published on May 25, 2024 10:33:37 AM ● Video Link: https://www.youtube.com/watch?v=qnfDnGsyMwg

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Let's Play

Duration: 37:12

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I think I'm making progress. The TL;DW summary is: doesn't seem to work on initial power-on (i.e. powered off for some time), but after replacing the original КС573РФ2 EPROM containing the Monitor software (and Soviet IC socket) with a 2716 EPROM & new IC socket it does now seem more stable on subsequent power-ons. However the characters are wrong ... it prints:

"АДПФА%БЦ" ... "ADPFA%BC"

instead of

*АЛЬФА-БК* ... *ALPHA-BK*

The Alpha-BK Monitor ROM can be found on my Discord in the "альфа-бк-alpha-bk" channel.

So the next thing to do will be desoldering the character ROM and installing a socket and a replacement 2716.

If this clears the issue ... I'm assuming the character ROM is getting the correct addresses from the 8275 CRT controller but is outputting the wrong data ... then it'll be back into the case to try the ... ahem ... "keyboard" out.

I was able to burn new 2716 EPROMs using a combination of my Book 8088 and AR Labs' AR-32A EPROM programmer (runs on DOS and uses a parallel port):
https://www.arlabs.com/eprom_plus.html

So sick and tired of my Chinese Wellon programmer crashing my Windows machine.

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