- Joined
- Nov 29, 2005
- Posts
- 4,275
OK,
Turns out Capcom did the same stupid thing as SNK... The board is silkscreened for a Z80A and they put a cheaper, slower rated Z80 on it. That makes this component very suspect if you have audio problems.
However, that's not always the problem on the board.
Tools needed: Multimeter to check for bad traces and a logic probe (preferably one with audio) - bonus if you have an oscilloscope.
Symptom: No FM audio or no audio at all: (And no suicide battery on a QSound audio board)
First check the YM3012 DAC IC. If there is audio coming off of it check the analog part of the audio circuit. The audio part of the logic probe will help here. Look for bad op amps or capacitors. Check for a broken volume pot. If there's no audio coming off of the YM3012 DAC then check the digital portion of the audio circuitry.
To troubleshoot the digital section start by checking the EPROM in socket 9 - the Audio EPROM. Are there any signals on the data lines? No? Check the reset line on pin 26 as you power up the board. If it starts out low then flips to high (after a small pause) then the reset line is OK.
If the reset line is bad, trace it back and fix it.
Next check the clock line on pin 6 of the Z80. If it is bad, replace the 3.579 oscillator. If it is good, replace the CPU.
If the data lines and address lines show signals then check pins 2, 5, and 6 on the YM2151. These are the IRQ*, RD*, and WR* signals. If they are stuck high or low then replace the CPU.
If replacing the CPU at this point doesn't solve the issue try replacing the SRAM IC. (2k x 8 - a 6116 SRAM IC can be used to replace it)
If there is activity on those lines of the YM2151 then check pin 21 of it. It will have a steady pulse if no audio is coming out (Serial Data out). When audio is coming out there will be a series of scratchy pulses on it - this is more evident if your logic probe has audio. If there is no audio pulses coming out on pin 21 then replace the YM2151.
Your FM audio should now be working.
The non-FM sound effects (voice, punching, and other sounds) are simply controlled by the OKI M6295 IC. Check EPROMs 18 and 19 as the digital code for the sound effects is stored there. Repair any bad traces or replace any bad EPROMs. Double check to make sure the jumpers for the EPROMs are set correctly for the EPROM type used. (There's another post on the forum on how to set the jumpers)
Enjoy!
RJ
Turns out Capcom did the same stupid thing as SNK... The board is silkscreened for a Z80A and they put a cheaper, slower rated Z80 on it. That makes this component very suspect if you have audio problems.
However, that's not always the problem on the board.
Tools needed: Multimeter to check for bad traces and a logic probe (preferably one with audio) - bonus if you have an oscilloscope.
Symptom: No FM audio or no audio at all: (And no suicide battery on a QSound audio board)
First check the YM3012 DAC IC. If there is audio coming off of it check the analog part of the audio circuit. The audio part of the logic probe will help here. Look for bad op amps or capacitors. Check for a broken volume pot. If there's no audio coming off of the YM3012 DAC then check the digital portion of the audio circuitry.
To troubleshoot the digital section start by checking the EPROM in socket 9 - the Audio EPROM. Are there any signals on the data lines? No? Check the reset line on pin 26 as you power up the board. If it starts out low then flips to high (after a small pause) then the reset line is OK.
If the reset line is bad, trace it back and fix it.
Next check the clock line on pin 6 of the Z80. If it is bad, replace the 3.579 oscillator. If it is good, replace the CPU.
If the data lines and address lines show signals then check pins 2, 5, and 6 on the YM2151. These are the IRQ*, RD*, and WR* signals. If they are stuck high or low then replace the CPU.
If replacing the CPU at this point doesn't solve the issue try replacing the SRAM IC. (2k x 8 - a 6116 SRAM IC can be used to replace it)
If there is activity on those lines of the YM2151 then check pin 21 of it. It will have a steady pulse if no audio is coming out (Serial Data out). When audio is coming out there will be a series of scratchy pulses on it - this is more evident if your logic probe has audio. If there is no audio pulses coming out on pin 21 then replace the YM2151.
Your FM audio should now be working.
The non-FM sound effects (voice, punching, and other sounds) are simply controlled by the OKI M6295 IC. Check EPROMs 18 and 19 as the digital code for the sound effects is stored there. Repair any bad traces or replace any bad EPROMs. Double check to make sure the jumpers for the EPROMs are set correctly for the EPROM type used. (There's another post on the forum on how to set the jumpers)
Enjoy!
RJ
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