Galaga

I have managed to acquire 3 Midway Galaga boards (original two layer sandwich boards) and 2 Gallag bootleg Galaga boards which have been an on-going project to repair.

Two of the Midway boards work perfectly – both are Galaga CPU and Video original boards, and all the EPROMs and custom chips check out fine.

One of the other Midway boards is a Bosconian CPU board combined with a Galaga Video board. This combination is valid as Bosconian and Galaga CPU boards are (virtually?) identical, being only the dip-switches that are different (or so the web implies).

You do need a Galaga Video board though, as Bosconian and Galaga are different when it comes to the video hardware (or so MAME claims…)

This board originally booted to a screen semi-full of yellow 0 characters and a few artefacts in the background, however switching the Video board for another known working one, would make the game fire up correctly.

On the Video board it has socketed Video 2114 RAM on chip positions 3E, 3F, 3H, 3J, 3K AND 3L so I removed and swapped around a few of these and now the board boots, but I’ve lost the video output.

I checked the custom 07XX chip at 1N and managed to break one of the legs of it while cleaning it :/ Not a problem, just re-socketed the chip with 2 14 pin sockets and re-soldered the leg and tested the 07XX chip in another board, and all works fine – so that’s not the issue…

Next steps are to get some replacement 2114 RAM to test, and potentially some replacement RAM for the 2147 RAM for those in sockets 6C, 6D, 6E, 6F and 6J, 6K, 6L, 6M

One of the other repairs suggest that the 74LS

Interestingly the video RAM can be strapped in two ways (referred to as “Video RAM Kit” – “Option 1” and “Video RAM Kit” – “Option 2” on the schematics).

“Option 1”, as this board has uses 8 x 2147 RAM (4K x 1) in sockets 6C – 6F and 6J to 6M, whereas “Option 2” uses 2 x 2148 RAM (1k x 4) in sockets 6B and 6H (I believe 2149 are compatible with 2148 and can be used instead).