Mortal Kombat Y-Unit Rev3 - Constant beeping sound

PCB problems and fixes
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TulioAdriano
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Mortal Kombat Y-Unit Rev3 - Constant beeping sound

Post by TulioAdriano »

Hi all.

I just received a Mortal Kombat Y-Unit Rev3, the seller said there was no sound, and in fact there wasn't. The sound board had a potentiometer soldered directly to P5 connector, but one of the joints had come loose.
After reconnecting the potentiometer, however, the only sound I get is the boot-up beep doing "ding, ding, ding, ding" on an endless loop.

I appreciate anyone's input on this. Any ideas?
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TulioAdriano
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Re: Mortal Kombat Y-Unit Rev3 - Constant beeping sound

Post by TulioAdriano »

Solved the problem.

Turns out crystal Y1 had a broken leg. It's a NTSC Frequency (3.579545 MHz) crystal used to clock the YM2151. Had to replace the crystal and the two neighbouring C49 and C47 capacitors which have 100 pF capacitance to make that particular crystal oscillate.

After replacing with a new 3.579545 MHz crystal and the appropriate 18 pF capacitors, I could see activity coming out of YM2151 into its YM3012 DAC, but no sound out of the output pins. Replaced the YM3012 with a spare and sound started to happen. Reseated the original YM3012 and sound continued to work.

I guess this ding ding sound is something particular that will happen if a fault is detected with the sound board, since it was obviously not coming out of the FM chip.

All diagnostics pass, time to tell those people from outworld who's in charge.
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cools
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Re: Mortal Kombat Y-Unit Rev3 - Constant beeping sound

Post by cools »

Nice fix! :D
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