Space Guerilla

I don't think you have any EPROMs missing, from mame it looks like there is a total of 12K programme, which will be on the 6 EPROMs on the board.  I'm guessing 5 & 6 are "missing" because of the (deliberate) gap in the ROM memory map

When I was trying to identify the board I read the EPROMs, I've uploaded the contents to http://www.ukvac.com/forum/uploads/183/SG.zip

Bear in mind in mame it uses 12 x 1K images, so the board looks like it's been re-strapped for the 6 x 2K images

Burned the roms with the proper  images supplied from phil and now getting somewhere.

Most of the time getting random bits of game graphics mixed with garbage but a couple of times got this:

It's stuck there so the game isn't running and for some reason the text and graphics are upside down but it's better than the blank screen I was getting.

Replaced the four 2114 ram chips on the CPU board and got demo mode running up until the space ship descends at which point it restarts the demo but as far as I can tell it's not watchdogging.

I'm guessing the descending spaceship is a sprite so maybe that's causing the problem.

Graphics are still upside down as well.

Will keep digging.

Did the game not use a mirrored cab which would explain the backward text?

Bit more progress.

I managed to get a leg outside of the socket on eprom 4 and fixing that gives me the full demo with the ship flying down and the little green man running up and down.

Can't seem to start a game up though and I'm wondering if it might be like the explorer I fixed that instead of the controls going to GND they were going to +22V.

Will have to trace the inputs but first I want to fix the upside down mirrored graphics problem.

Fortunately this boardset seems to use a pair of 74LS194 chips to turn the bytes of video data into a stream of bits for output like other boardsets do.

I have found that pin 9 on both the chips is stuck high which I think is the problem as pins 9 and 10 set the direction the bytes are streamed so in this case the bytes are being streamed in reverse.

Going to trace what drives pin 9 and see if anything is wrong in the earlier circuitry.

OMG OMG OMG OMG OMG!!!!!

So it's been a while since I dared to try and fix this one.

Since I didn't have any information and felt like I lacked the knowledge and experience to diagnose this from scratch it's been left for *checks date* WOW,nearly two years. Where does the time go.

Not checked the sound yet but from previous tests I think the controls work.

Will post later on what i did but instead of trying to figure it out using logic I just used my slice to slowly check every chip and was going to start replacing the ones that showed the worse results (some chips can show bad because of the way the circuit is designed) and just change them one by one but fortunately piggybacking a couple brought this back which is down to luck more than judgement.

There's still an issue with one chip that might be a loose leg because the graphics corrupt sometimes but I know where that fault is.

Can't wait to get this fully working and playing it in my cab.

I played it a lot in an arcade in Dawlish Warren (the only place I ever saw it) so it's a real bit of nostalgia for me.

I know it's on mame but it's not the same.