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xodaraP

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Hi everyone,
I'm getting an error on a Truxton board I've been repairing that's suffered some major damage but it's now at least booting to an error screen. I'm getting an error screen complaining of a lookup error at 01447FF which from looking at the MAME driver I can see is the upper boundary for the background pallette RAM.

There are 7 different sets of RAM on this board, so I'm trying to identify which is which.

6264 x 5 (Underneath ROMs 1-4 - maybe sprites?)
6116 x 2 (Above SCU - colour output stage)
62256 x 4 (Above large custom D65018R)
6264 x 2 (Main CPU WORK RAM)
6116 x 1 (Sound RAM)
6116 x 2 (Bottom left)
6116 x 1 (Right next to FCU)

I'm thinking the pallette RAM is most likely the 4x62256 and this does duty for both background and foreground, but I was hoping someone might be able to confirm.

Thanks
 
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xodaraP

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Troubleshooting information in case anyone is looking for this information. I have metered out the locations from the 62256 SRAM to the custom PGA - I was thinking one of these traces might have been bad. These locations assume that you are looking at the underside of the board with the JAMMA edge facing left, SRAMs are above the PGA.

I have named the locations as Row.Pin to make it easier to keep track - all row numbers are horizontal rows. For example, 1.2 is the top row, second pin, 2.4 is second row down, fourth pin in.

Address pins are the same across all 4 RAM chips

Pin 1 - 2.2
Pin 2 - 2.3
Pin 3 - 2.1
Pin 4 - 6.4
Pin 5 - 5.3
Pin 6 - 4.2
Pin 7 - 3.1
Pin 8 - 6.3
Pin 9 - 5.2
Pin 10 - 4.1
Pin 14 - GND
Pin 20 - GND
Pin 21 - 5.4
Pin 22 - 1.3
Pin 23 - 1.2
Pin 24 - 4.3
Pin 25 - 3.2
Pin 26 - 3.4
Pin 27 - 1.4
Pin 28 - Vcc

The data pins are different for each of the 4 RAMs - I started from the bottom RAM IC and worked my way up

Bottom
Pin 11 - 1.5
Pin 12 - 2.5
Pin 13 - 3.5
Pin 15 - 4.5
Pin 16 - 1.6
Pin 17 - 2.6
Pin 18 - 3.6
Pin 19 - 4.6

Second from bottom
Pin 11 - 1.7
Pin 12 - 2.7
Pin 13 - 3.7
Pin 15 - 4.7
Pin 16 - 1.9
Pin 17 - 2.9
Pin 18 - 3.9
Pin 19 - 4.9

Third from bottom
Pin 11 - 1.10
Pin 12 - 2.10
Pin 13 - 3.10
Pin 15 - 4.10
Pin 16 - 1.11
Pin 17 - 1.15
Pin 18 - 3.11
Pin 19 - 4.11

Top
Pin 11 - 1.8
Pin 12 - 2.8
Pin 13 - NC
Pin 15 - NC
Pin 16 - NC
Pin 17 - NC
Pin 18 - NC
Pin 19 - NC
 
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