System 16B no sound

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    • System 16B no sound

      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!
    • Probing around the 315-5250 on the ROM board and I'm seeing a ton of pins with no signals (I'll need to go through pin by pin and make notes), but in the meantime I'm trying to come up with a pinout since I haven't seen it documented anywhere. Below is what I've got so far.

      I need to go back over it with a micrograbber so I can see if any of the '?' pins go to the 315-5248 on the underside, or if they travel through a via and lose connection somewhere on the underside.

      If anyone has a pinout for the 5250, that would be really helpful right about now.

      315-5250

      1 -> gnd
      2 -> CN4, A3
      3 -> CN4, B3
      4 -> CN4, A4
      5 -> CN4, B4
      6 -> CN4, A5
      7 -> CN4, B5
      8 -> CN4, A6
      9 -> CN4, B6
      10 -> CN4, A7
      11 -> CN4, B7
      12 -> CN4, A8
      13 -> CN4, B8
      14 -> vcc
      15 -> gnd
      16 -> CN3, A10
      17 -> CN3, B9
      18 -> CN3, A9
      19 -> CN3, B8
      20 -> CN3, A8
      21 -> CN3, B7
      22 -> CN3, A7
      23 -> CN3, B6
      24 -> CN3, A6
      25 -> CN3, B5
      26 -> CN3, A5
      27 -> CN3, B4
      28 -> CN3, A4
      29 -> CN3, B3
      30 -> CN3, A3
      31 -> gnd
      32 -> CN3, B2
      33 -> CN3, A2
      34 -> CN3, B1
      35 -> CN3, A1
      36 -> CN4, B16
      37 -> IC4, pin 5
      38 -> IC16, pin 8
      39 -> RA1, pin 2
      40 -> RA1, pin 3
      41 -> ?
      42 -> ?
      43 -> ?
      44 -> vcc
      45 -> gnd
      46 -> ?
      47 -> ?
      48 -> ?
      49 -> ?
      50 -> ?
      51 -> ?
      52 -> ?
      53 -> gnd
      54 -> gnd
      55 -> ?
      56 -> RA1, pin 6
      57 -> RA1, pin 7
      58 -> RA1, pin 8
      59 -> RA1, pin 9
      60 -> ?
      61 -> gnd
      62 -> ?
      63 -> ?
      64 -> ?
      65 -> ?
      66 -> ?
      67 -> ?
      68 -> ?
      69 -> ?
      70 -> ?
      71 -> ?
      72 -> ?
      73 -> ?
      74 -> vcc
      75 -> gnd
      76 -> ?
      77 -> ?
      78 -> ?
      79 -> 80
      80 -> 79
      81 -> ?
      82 -> R1
      83 -> vcc
      84 -> vcc
      85 -> ?
      86 -> ?
      87 -> R2
      88 -> ?
      89 -> RA2, pin 9
      90 -> RA2, pin 8
      91 -> gnd
      92 -> RA2, pin 7
      93 -> RA2, pin 6
      94 -> RA2, pin 5
      95 -> RA2, pin 4
      96 -> RA2, pin 3
      97 -> RA2, pin 2
      98 -> RA3, pin 9
      99 -> RA3, pin 8
      100 -> RA3, pin 7
      101 -> RA3, pin 6
      102 -> RA3, pin 5
      103 -> RA3, pin 4
      104 -> vcc
      105 -> gnd
      106 -> RA3, pin 3
      107 -> RA3, pin 2
      108 -> ?
      109 -> vcc
      110 -> vcc
      111 -> IC16, pin 12
      112 -> ?
      113 -> IC17, pin 3
      114 -> IC17, pin 6
      115 -> IC16, pin 4
      116 -> IC18, pin 1
      117 -> CN4, B1
      118 -> IC18, pin 3
      119 -> CN4, B2
      120 -> ?

      The post was edited 1 time, last by benime ().