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Plotting 4-in-1 Homebrew Multi

twistedsymphony

twistedsymphony

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Not my project, @AlxUnderBase pointed this little multi kit by BrK out to me and I thought it was interesting enough to share.

IMG_20250319_202721.jpg


it's a 4-in-1 bank switcher for a Taito Plotting PCB: https://oshpark.com/shared_projects/PcfvgpI6
Interestingly while 1 game is Plotting, the other 3 games are homebrew ports

Sokoban L.E. (homebrew) https://www.ukvac.com/forum/threads/new-game-release-sokoban-le-for-taito-l-system.36006/
SQIJ! (homebrew) https://tardis.dk/wordpress/?page_id=1695
The Speccies 2(homebrew) https://www.ukvac.com/forum/threads/new-game-release-speccies-2-for-taito-l-system.36007/

There's one for sale assembled with pictures here: https://www.ukvac.com/forum/threads/taito-l-system-4in1-pcb.86811/

It appears to use Atmel AT49F002T https://www.alldatasheet.com/datasheet-pdf/download/56178/ATMEL/AT49F002T.html
which look to be essentially Electrically erasable 27c020 so I don't see why normal ROMs wouldn't work.

While the Osh-Park link says "Puzznic", the Puzznic PCB is slightly different than Plotting and has a some of the main board circuit offloaded to a sub-board. So I'm skeptical that this could be used on Puzznic without undoing some of the factory modifications, or at very least a PAL swap. If you want to try it out I'd recommend sticking to a Plotting donor.
 
The board was orginaly designed from Puzznic since it was the only one I had. It should work with any 27C020 eproms.
This is how it look on puzznic. No need to remove the top board. If one wants to remove it, the PAL should be moved from the to board to the main board.
For the DIP switches, one can cut a 6 or 8. be careful to leave the remaining 2 undamaged.
IMG_20250426_172737.jpg
IMG_20250426_172748.jpg
 
I finally got the PCBs for this in that I ordered from OshPark.
this is an incredibly tiny multi. the pictures don't do it justice!

Here's a mini guide on building.

Parts you'll need:
1x PCB
6x 14pin socket headers rows (84 pins total) (round pin style like this: https://www.amazon.com/2-54mm-Plated-Single-Straight-Header/dp/B083RYP6G5)
3x 32pin IC sockets
2x 4.7k resistors
1x 2-position DIP switch

soldering the kit:
You'll need install the socket headers and IC sockets in a specific order otherwise you'll paint yourself into a corner and be unable to install the next part.
the order is
1 = the socket headers for IC2
2 = the IC socket for IC2
3 = the socket headers for IC4
4 = the IC socket for IC4
5 = the socket headers for IC6
6 = the IC socket for IC6
solder_order.jpg


The socket headers are the shorter rows and the sockets are the longer rows.
After you install a pair of socket headers the IC socket that gets installed over it will likely not sit flush do to the solder side of the socket header pins. What I did is before installing the IC socket I used flush cutters to trim down the solder side of the socket header row under the IC socket I'm about to install. Then I reflowed the solder for this row. the result is instead of a pin sticking up, you have just a minor solder bump as the pin end is now flush with the PCB and it wont interfere (much) with the socket.

once you've got all the socket headers and IC sockets installed then it's just a matter of installing the dip switch and resistors, no tricks here.
IMG_20250517_164100426_HDR.jpg


building the ROMs:
To build the ROM files I put together a little build script (see attached .zip file). Plotting you can get from MAME, and downloads for the 3 homebrew games are linked in the top post.

extract each zip into it's own folder and place the build script files in the root. it should look like this:
rom_build_folder.jpg


then run the .bat file and it should generate 3 ROM files in an "output" folder. Each 256K in size, if they're smaller then something in the script failed.
output_folder.jpg


installing the multi
Burn the 3 ROM files in the output folder to 27c020 or 27c2001 EPROMs and and install on the multi in the sockets that match the file names.
Remove the 3 original ROMs from your Plotting (or Puznic) PCB and install the multi kit into the now empty sockets.

thats it!

IMG_20250517_181743706.jpg


This is a pretty neat little multi. Thanks @Georgian2 !
 

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