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Lurch666 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Topic: Space Guerilla
    Posted: 07 Jan 2021 at 10:19am
Since there's no schematics or other info I can find on this game I will post what I find while getting it working.
It's a cage with a CPU board,two video boards an I/O board and a sound board on the outside.
Wired it up for +5 and GND plus RGB and got a sync signal but no video output at all.
Pulling the CPU board I saw why:


Six eproms are missing but even worse is that they are TMS2716.
I hadn't supplied the -5V and +12V they need but it wouldn't have worked anyway due to the missing eproms.
Even my pinmaster 48 won't read them so I have no way of verifying the ones that are present and no way of burning the missing chips.

I was thinking about either making adaptors or modifying the PCB to accept normal 2716 but making 12 adaptors is a lot of work and I didn't want to do any permanent mods to the PCB since it's a rare original (as far as I can tell).

Then I noticed this part of the CPU board:


Checking with my continuity meter I verified it was strapping for different sorts of eproms.

Using this handy guide from Mike's arcade:



I figured out how to change the connections to set it up for 2716 eproms:


Now I have to dig out 12 2716 eproms to populate all the sockets. I have about 6 spare so will pull others from working boards and erase them to use in this board (I do have more 2716s coming in the post but don't want to wait for them to come from China).

Next I'll see if sorting out the eproms puts anything up on the screen.
I also noticed what might be missing 2114 ram chips at 4B and 5B but will try without replacing them first and if i get no joy I'll put sockets and new chips in next.


Edited by Lurch666 - 07 Jan 2021 at 10:22am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote philmurr Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jan 2021 at 11:18am
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

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 07 Jan 2021 at 10:32pm
Well I did notice it watchdogging with the original roms in before I changed the strapping but I missed that the mame images are 1024 where 2716 eproms are 2048 so I've got the images wrong.
Will erase and try with six eproms with the code you have supplied and see where that gets me.

Thanks dude.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2021 at 3:29pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote yorkshire_spam Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2021 at 3:54pm
Keep digging! You'll get there!
I've just repaired some damaged tracks on a PCB and that seems to have made it WORSE!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2021 at 5:34pm
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.Wink
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2021 at 6:49pm
Now I have something on the screen I can start finding out the other faults with this boardset.
The problem is it's a five board set with connectors on both sides of the boards.
It runs without the sound board but without the I/O board I get some of the title screen but it's constantly resetting like it's getting credits but it's enough to try and find out why the text is upside down.
The two graphics board have a specific position in the stack but I have found that they can be reversed and the game still works as far as it does.
So what this means is I can run the game enough with either graphic board exposed so I can probe and slice it.
There's several fujitus so I'll start by checking those and if they are OK I'll use the video probe and see what specific parts are generating the graphics.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote philmurr Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2021 at 6:51pm
Did the game not use a mirrored cab which would explain the backward text?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 13 Jan 2021 at 7:02pm
From memory it wasn't a mirrored cab plus if you look at the screen I posted earlier the text is in the correct order it's just the letters are upside down.

EDIT:and mirrored.


Edited by Lurch666 - 14 Jan 2021 at 12:28am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Lurch666 Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2021 at 12:24pm
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.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote yorkshire_spam Quote  Post ReplyReply Direct Link To This Post Posted: 14 Jan 2021 at 12:32pm
Nice work!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hurray Banana Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jan 2021 at 7:05am
Excellent work so far
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