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IREM BomberMan World no audio diagnostics help request. YM2151?

Kujako

Kujako

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Working on breathing life back into a BomberMan World board I picked up as junk from a user here. Hammy was able to help me get working ROMs, and the game now plays correctly. However I've getting no audio. I hear the expected white noise from the amp, so thinking that's OK. I see the YM2151 and am getting an expected digital clock signal out (see pictures) from pins 23 and 24. Just not sure where to look next... I assume there is a DAC chip on here, but my vision may be failing me because I can't find it (also kind of rusty on the ol' oscilloscope...).

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Hammy said:
Check the outputs on the YM 3014 , and be sure the sound program rom is the M97 version and NOT the m99 version.
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On the YM3014, I see a square wave in (PIN2) and what is either audio or static out (PIN3 in the low mv range).... going to try and cobble together an audio probe this weekend I think. But assuming the input signal is valid, the YM2151 would seem to be OK and things are getting at least as far as the YM3014.
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Hammy said:
That signal maybe sound :)

Another thing to check is the caps, if they are "elna" then are the type that go bad...
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Yeah hoping it's audio, will check when I get an audio probe put together. The capacitors are elna, and if I determine I'm getting audio out of the DAC I'll look at them as well as the MB3730A driver.
 
@Hammy even if it's not the capacitors, if I get things working I'll want to recap it. Looking to put together a capacitor list since I don't have a huge selection on hand. From my googling, this is what I see for the IREM M97.

470uf / 25v - C203
220uf / 10v - C201
100uf / 25v - C210
47uf / 16v - C209
22uf / 25v - C204
1uf / 50v - C202, C214, C216
10uf / 16v - C41

Does this match your experience?
 
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OK, so few things...

1) Audio probe built and tested with a signal generator.
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2) Confirmed a digital signal into Y3014 pin 4 (was checking pin 2 before which is the clock, now I see varied cycles that would indicate a digital signal)
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3) Audio probe hooked to pin 2 of the Y3014, just get a faint hiss
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4) Back on the oscilloscope I see a sine wave on pin 2, but it's constant and at only a few nanoseconds, so seems like just static
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Conclusion, possible dead Y3014? Would appreciate anyone's opinion, cheap enough to buy another Y3014 and piggy back it I guess, but I could get a sandwich instead...
 
Looks like things are good until the dac. I would replace the YM3014 and if there is an opamp after it (which it should) that also.
 
Hammy said:
Chop the old one out, remove the legs and fit a new one. Don't do this with dead parts, especially audio.
3014 is common problem swapping it out should do the trick, opamp normally fine after these faults.
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Fair enough... but if I'm going to go the non-lazy route I'll just remove the old one with my desoldering gun and put in a 8 pin socket.

Derick2k said:
Looks like things are good until the dac. I would replace the YM3014 and if there is an opamp after it (which it should) that also.
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Brain may be failing me... opamp? Would that be the MB3730A?
 
It should be an ic after the 3014 , probably says TL on the silkscreen. If you trace the output of the 3014 it should lead to the opamp. I would say get it just in case.
 
Derick2k said:
It should be an ic after the 3014 , probably says TL on the silkscreen. If you trace the output of the 3014 it should lead to the opamp. I would say get it just in case.
Click to expand...

This guy? Thought that was just a memory buffer... not having a lot of luck finding one one the ebays, and I managed to clog my desoldering gun (think one of the pins of the YM3014 got sucked up). So I think that's all I've got in me for the day. Will pick this up tomorrow.
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2 opamps :D

Yeah the 064d is one and the other is the LM358F, not sure what they are doing, maybe the 064 feeds the amp and the other offers line level out to cn1 or cn2??

But first replace the dac and see if that solves all your troubles.
 
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Derick2k said:
2 opamps :D

Yeah the 064d is one and the other is the LM358F, not sure what they are doing, maybe the 064 feeds the amp and the other offers line level out to cn1 or cn2??

But first replace the dac and see if that solves all your troubles.
Click to expand...

Can't seem to find either the 064D or the LM358F locally... so won't worry about then unless the YM3014 isn't the issue. Unclogged my desoldering gun, and while not my best work I have the socket in for when a replacement arrives.


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Yup, just change the dac first and go from there if there are any issues after that.
 
Derick2k said:
Yup, just change the dac first and go from there if there are any issues after that.
Click to expand...

New 3014 is in, but no change. Getting the same static on pin 2. Still looks like digital input on pin 4. But it may be gobbledygook. So going to take a closer look at and perhaps swap out the 2151.
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And eBay tells me I already have a replacement around here someplace (unless I installed it already in a different board)... neat?
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