you can use pinwiki, but frankly it's the king of confusion in my eye.
Here's the instructions for doing the single 2732 EPROM at u2 from my original notes and documents.
Mod2: Single 2732 at U2 on a Bally -17 or Stern M-100 MPU board.
Note this modification is an excellent choice for -17 and M100 MPU boards because it uses a single 2732 EPROM at U2 instead of two ROMs at U2 and U6. This is especially helpful because these boards often need their chip sockets replaced, so using one chip instead of two means less sockets to deal with. This modification combines the two original 9316 ROMs at U2 and U6 into one single 2732 EPROM at location U2. This works only for the early 1977 to 1979 games using 9316s at U2/U6. (Six games which include Black Jack, Night Rider, Mata Hari, Bobby Orr Power Play, Evel Knievel, Eight Ball, plus some Stern M100 games.)
Note this mod still allows the use of Leon's Test 2716 EPROM at U6 without any adaptor (just plug the 2716 directly into U6).
To combine the original 9316 (or 2716) U2 and U6 ROM computer files into a single 2732 U2 ROM file, use the following DOS command:
COPY /B U2ROM.716 + U6ROM.716 U2COMBO.732
Make sure you use the "/B" option in the copy command, as shown above. This binary copy command will combine the two files into one. Or you may just download the Bally -17 2732c Zip file with all these conversions for the six Bally games already done. Stern M100 software is already formatted for a single U2.732 in this Stern M100 2732c Zip file
In addition to the jumpers listed above (6-7, 8-10), you must also make the following cuts and jumps to the -17 or M100 board to use this configuration.
1. Make sure jumpers E6-E7 and E8-E10 are in place.
2. Remove any jumpers at E3-E4, and E1-E2.
3. On the solder side of the board, cut the trace leading to U18 pin 4.
4. On the solder side of the board, run a jumper from the via above U3 pin 6 (that had its trace cut in the prior step) to U18 pin 5. This connects U18 pin 5 to U2 pin 18.
5. On the componet side of the board, find U2 pin 13 (top right hand corner). Slightly higher and to the right is a via ("trace thru dot") with a trace going straight down. Cut this trace to separate the via from this trace.
6. On the component side of the board, run a jumper from the above via ("trace thru dot") to jumper pad E4. This connects jumper pad E4 to U2 pin 21.
7. On the component side of the board, notice the large GND trace that runs to the right of the ROM sockets. To the right of the U2 ROM socket, scrape the green solder mask from this large GND trace and jump a wire from this GND trace to the jumper pad E3. This connects U2 pin 20 to ground.
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