Dragon Ball Z Repair Logs

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Repairer: cal2
Forum Thread: Dragonball Z PCB Repair

Symptoms

Repeating graphics on first scroll plane:

Pcb repair dragonball z 1.jpg

Pcb repair dragonball z 2.jpg


Repair

Based on the mame driver, I found that the graphics for this plane come from 222a09.25l (K053536 PSAC-2 #2).

The board passes the PSAC2 rom test, so I assumed the mask rom is good. Note that the pinout is compatible with M27C160.

I reproduced the problem on mame by changing the way the pixels bits are fetched from this eprom.

Normaly it should be:

0 1 2 3 4 5 6 7 8 9 a b c d e f

But is displays like this:

0 1 2 3 0 1 2 3 8 9 a b 8 9 a b

In binary this means:

3210 3210
0000 0000
0001 0001
0010 0010
0011 0011
0100 0000
0101 0001
0110 0010
0111 0011
1000 1000
1001 1001
1010 1010
1011 1011
1100 1000
1101 1001
1110 1010
1111 1011

So it means bit 2 is likely stuck to 1 or 0.

Since the tiles are 16x16 in 4bpp, this means b0 isn't used. So, if b1 = A0 it means b2 = A1 on the mask rom.

Looking at A1 using a probe, i found it was bad compared to the other signals. It should be a squared signal of 1/2 frequency of A0. Instead, it is pulsing very quickly.

So A1 is bad. A1 is connected to O3 of 27F374 @ 24M.

I changed the IC to see but it didn't make changes.

After taking time tracing the board, I found that a pin of the custom chip 053936 @ J16 was desoldered and made contact to an other pin.

Fixing this pin, also fixed the graphic problem


Repair Logs converted to wiki format by Brad from Aussie Arcade.