I picked up a System 16B with 171-5797 ROM board (E-Swat, decrypted) from brentradio a couple weeks back and have been working on it off and on but I am stumped at this point. Game originally had graphics problems and no sound, but after dumping and verifying all ROMs, I found the Mask ROM at B1 was bad; replacing it fixed the graphics problem.
Audio jumpers have been verified (shorted on S11, S14, S16), A13 is the original EPR-12617 EEPROM and A11 is the original MPR-12616 Mask ROM.
As best I can tell, the problem is in the digital side of the audio generation circuit. When I increase the volume at the pot, the audible hum over the connected speakers increases.
I have no analog out on Pin 12 of the YM3012 DAC, but I am seeing a steady pulse from Pin 21 of the YM2151 received on Pin 4 of the DAC. The Z80 is alive and functioning (there's activity on the Address and Data lines at the Z80), but I've swapped it with a known working Z80B and no change. I've verified clock for the Z80 and YM2151 (5 and 4MHz, respectively).
When I check the Address and Data lines at the A11 and A13 ROMs, I have pulses on some of the Address lines but the Data lines are stuck either High or Low. Here's the relevant bits from my logic probing:
(pulsing means I saw a pulse but both the high/low indicators were lit on my logic probe)
z80
1 - a11 - low
2 - a12 - low
3 - a13 - low
4 - a14 - pulsing
5 - a15 - low
6 - clk - pulsing (clock measured at 5MHz)
7 - d4 - high
8 - d3 - low
9 - d5 - low, pulsing
10 - d6 - no signal
11 - +5V - high
12 - d2 - high
13 - d7 - low, pulsing
14 - d0 - low, pulsing
15 - d1 - high
16 - /int - low
17 - /nmi - high
18 - /halt - low
19 - /mreq - pulsing
20 - /irq - high
21 - /rd - pulsing
22 - /wr - high
23 - /busak - high
24 - /wait - high
25 - /busrq - high
26 - /reset - high
27 - /m1 - pulsing
28 - /refresh - pulsing
29 - gnd - low
30 - a0 - pulsing
31 - a1 - pulsing
32 - a2 - pulsing
33 - a3 - pulsing
34 - a4 - pulsing
35 - a5 - pulsing
36 - a6 - pulsing
37 - a7 - pulsing
38 - a8 - pulsing
39 - a9 - low
40 - a10 - low
A11 ROM
32 - vcc - high
31 - /pgm - high
30 - a17 - low
29 - a14 - low
28 - a13 - low
27 - a8 - pulsing
26 - a9 - low
25 - a11 - low
24 - /oe - low
23 - a10 - low
22 - /ce - high
21 - d7 - low
20 - d6 - low
19 - d5 - low
18 - d4 - high
17 - d3 - low
16 - gnd - low
15 - d2 - high
14 - d1 - high
13 - d0 - low
12 - a0 - pulsing
11 - a1 - pulsing
10 - a2 - pulsing
9 - a3 - pulsing
8 - a4 - pulsing
7 - a5 - pulsing
6 - a6 - pulsing
5 - a7 - pulsing
4 - a12 - low
3 - a15 - low
2 - a16 - low
1 - vpp - high
A13 ROM
28 - vcc - high
27 - a14 - pulsing
26 - a13 - low
25 - a8 - pulsing
24 - a9 - low
23 - a11 - low
22 - /oe - pulsing
21 - a10 - low
20 - /ce - pulsing
19 - d7 - low
18 - d6 - low
17 - d5 - low
16 - d4 - high
15 - d3 - low
14 - gnd - low
13 - d2 - high
12 - d1 - high
11 - d0 - low
10 - a0 - pulsing
9 - a1 - pulsing
8 - a2 - pulsing
7 - a3 - pulsing
6 - a4 - pulsing
5 - a5 - pulsing
4 - a6 - pulsing
3 - a7 - pulsing
2 - a12 - low
1 - vpp - high
Not sure what else to check at this point. I've validated continuity for the Z80, YM2151, YM3012, A11 and A13 ROMs, as well as reflowed the pins on the 315-5195 since the Address and Data lines are connected there.
Any ideas of what to check next (I've already been stuck in a loop checking the SRAM at D14, the LS273 at E19, and the CK2605) would be greatly appreciated. If there's any more information y'all want, just ask.
Thanks for any help you can offer!
Audio jumpers have been verified (shorted on S11, S14, S16), A13 is the original EPR-12617 EEPROM and A11 is the original MPR-12616 Mask ROM.
As best I can tell, the problem is in the digital side of the audio generation circuit. When I increase the volume at the pot, the audible hum over the connected speakers increases.
I have no analog out on Pin 12 of the YM3012 DAC, but I am seeing a steady pulse from Pin 21 of the YM2151 received on Pin 4 of the DAC. The Z80 is alive and functioning (there's activity on the Address and Data lines at the Z80), but I've swapped it with a known working Z80B and no change. I've verified clock for the Z80 and YM2151 (5 and 4MHz, respectively).
When I check the Address and Data lines at the A11 and A13 ROMs, I have pulses on some of the Address lines but the Data lines are stuck either High or Low. Here's the relevant bits from my logic probing:
(pulsing means I saw a pulse but both the high/low indicators were lit on my logic probe)
z80
1 - a11 - low
2 - a12 - low
3 - a13 - low
4 - a14 - pulsing
5 - a15 - low
6 - clk - pulsing (clock measured at 5MHz)
7 - d4 - high
8 - d3 - low
9 - d5 - low, pulsing
10 - d6 - no signal
11 - +5V - high
12 - d2 - high
13 - d7 - low, pulsing
14 - d0 - low, pulsing
15 - d1 - high
16 - /int - low
17 - /nmi - high
18 - /halt - low
19 - /mreq - pulsing
20 - /irq - high
21 - /rd - pulsing
22 - /wr - high
23 - /busak - high
24 - /wait - high
25 - /busrq - high
26 - /reset - high
27 - /m1 - pulsing
28 - /refresh - pulsing
29 - gnd - low
30 - a0 - pulsing
31 - a1 - pulsing
32 - a2 - pulsing
33 - a3 - pulsing
34 - a4 - pulsing
35 - a5 - pulsing
36 - a6 - pulsing
37 - a7 - pulsing
38 - a8 - pulsing
39 - a9 - low
40 - a10 - low
A11 ROM
32 - vcc - high
31 - /pgm - high
30 - a17 - low
29 - a14 - low
28 - a13 - low
27 - a8 - pulsing
26 - a9 - low
25 - a11 - low
24 - /oe - low
23 - a10 - low
22 - /ce - high
21 - d7 - low
20 - d6 - low
19 - d5 - low
18 - d4 - high
17 - d3 - low
16 - gnd - low
15 - d2 - high
14 - d1 - high
13 - d0 - low
12 - a0 - pulsing
11 - a1 - pulsing
10 - a2 - pulsing
9 - a3 - pulsing
8 - a4 - pulsing
7 - a5 - pulsing
6 - a6 - pulsing
5 - a7 - pulsing
4 - a12 - low
3 - a15 - low
2 - a16 - low
1 - vpp - high
A13 ROM
28 - vcc - high
27 - a14 - pulsing
26 - a13 - low
25 - a8 - pulsing
24 - a9 - low
23 - a11 - low
22 - /oe - pulsing
21 - a10 - low
20 - /ce - pulsing
19 - d7 - low
18 - d6 - low
17 - d5 - low
16 - d4 - high
15 - d3 - low
14 - gnd - low
13 - d2 - high
12 - d1 - high
11 - d0 - low
10 - a0 - pulsing
9 - a1 - pulsing
8 - a2 - pulsing
7 - a3 - pulsing
6 - a4 - pulsing
5 - a5 - pulsing
4 - a6 - pulsing
3 - a7 - pulsing
2 - a12 - low
1 - vpp - high
Not sure what else to check at this point. I've validated continuity for the Z80, YM2151, YM3012, A11 and A13 ROMs, as well as reflowed the pins on the 315-5195 since the Address and Data lines are connected there.
Any ideas of what to check next (I've already been stuck in a loop checking the SRAM at D14, the LS273 at E19, and the CK2605) would be greatly appreciated. If there's any more information y'all want, just ask.
Thanks for any help you can offer!