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Kujako

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yes and no. An audio probe is a device that's basically a metal pin attached to an audio amp and a small speaker. so you can touch a pin on the circuit and "hear" the data on that pin.

think of it like an oscilloscope with audible output instead of visual

using that you can check the output pins of every chip in the audio circuit to determine where the failure point is.

you might be right that one of the clone parts damaged something else, but heck that can happen with some original parts fail too, it's best not to jump to conclusions until you've gone through all the basics first.
Gotcha, more or less what I was planning on trying via oscilloscope. Issue I had was that the CPS1 B board's in the way. I know people use rigs that moves the B+C to the bottom or similar, but I'm not up to building or buying such a thing. I guess I could try measuring from the bottom of the board. Will consider that next.

Checked pins 8 to 12 which should be the analog output of the YM3012 DAC, get a constant low buzz (which is what I hear from the amp if I crank up the volume a bit). So issue is either with the YM302, or before it.
IMG_0879.jpg
 
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Nebula

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Apart for those CPS1 stuff, I see lots of CPS2 stack from China, all of them without case and everything populated with eproms.
 

awbacon1

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It seems like eBay is flooded with a ton of chinese oddities lately
 

Kujako

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It seems like eBay is flooded with a ton of chinese oddities lately
Reaction to lock down I think, lots of people are spending their time on video games. But it's getting to be a problem. Here's an example. I contacted these sellers, and they won't even commit to sending a 10mhz or 12mhz board. They just have a pile of these weird boards with kludged sound systems. They grab one and ship it out, then you get what you get.

There are also a lot of B boards for CPS1 and CPS2 systems with suspect setups and rom hacks. Getting hard to find actual original hardware.
 

duffcon

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I feel like there's a shop in China who probably got a container of CPS1 stuff and is parting together boards.
 

Kujako

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And fair warning, the solder and flux they used is really nasty... been having a lot of issues getting the chips desoldered.
 

awbacon1

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I feel like there's a shop in China who probably got a container of CPS1 stuff and is parting together boards.
Their ingenuity should be commended though. Even if it’s hack and boot shit I’m always impressed what they manage to rig up
 

GeorgeSpinner

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twistedsymphony

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It was always my impression that some modifications needed to be made to the PCB that would disable Audio over JAMMA. and even then only some games supported "stereo" and even then it wasn't always real stereo but often just pre-mixed audio.

I'd be happy if that's not actually the case.
 

GoldenGlover

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I made a cable for my SF2T board (3 pin JST to stereo RCA) & notice a definite improvement in the audio over mono. It does sound “clearer” and a little more defined with sound effects being split between left & right channels. I think non stereo CPS1 games output mono from this connector but with one channel being weaker than the other. Either way, the most important thing from this CN5 connector is that it appears to be already line level which is a huge plus for anyone that has an amp feeding this audio to speakers!
96ABE93C-B9C4-4458-A66D-DCCB4A40D2A2.jpeg
 

GoldenGlover

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I made a cable for my SF2T board (3 pin JST to stereo RCA) & notice a definite improvement in the audio over mono. It does sound “clearer” and a little more defined with sound effects being split between left & right channels. I think non stereo CPS1 games output mono from this connector but with one channel being weaker than the other. Either way, the most important thing from this CN5 connector is that it appears to be already line level which is a huge plus for anyone that has an amp feeding this audio to speakers!
96ABE93C-B9C4-4458-A66D-DCCB4A40D2A2.jpeg
Also, the pot (VR1) for audio no longer raises or lowers the volume when using the CN5 connector (turning it while on makes no difference in output). O__o Appears that the audio volume from the CN5 is controlled from the amp you’re driving this into...
 

santa978

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I made a cable for my SF2T board (3 pin JST to stereo RCA) & notice a definite improvement in the audio over mono. It does sound “clearer” and a little more defined with sound effects being split between left & right channels. I think non stereo CPS1 games output mono from this connector but with one channel being weaker than the other. Either way, the most important thing from this CN5 connector is that it appears to be already line level which is a huge plus for anyone that has an amp feeding this audio to speakers!
96ABE93C-B9C4-4458-A66D-DCCB4A40D2A2.jpeg
will you sell this cable, if you do ill take 3
 

Kujako

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So looks like I ordered qty 100 74F74 chips to see if that was the problem rather than my intended 1. So.... if anyone wants one....
 

GoldenGlover

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I was reading that you need to remove vr1 to get clear sound from those pins and that only some games support stereo.

Do you know if that's accurate?

These guys seem to think so.

https://forum.arcadeotaku.com/viewtopic.php?t=37461

I don't really want to mod my board, but stereo sound would be nice.
You don’t have to remove VR1. The CN5 connector works without needing to use it as its line level output apparently isn’t attenuated by it (I have tried this in my pic/setup shown above). Just leave it in place...it will still work with JAMMA mono audio.
 

CoolFox

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Took over a year for mine to lose audio, and I'm at a loss as to how to repair it because it's such a departure from what it should be... so far tried swapping the crystal, the z80 and the YM2151 (there was a clone chip in it's place KA51) and nothing. Going to try putting a YM3012 in where they have a KA12 and see what happens. Then I'm about out of ideas.
IMG_0878.jpg


Step 0, make sure the z80 you are using is an actual Z80 cpu and not a Z80 SIO chip
 

Kujako

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Step 0, make sure the z80 you are using is an actual Z80 cpu and not a Z80 SIO chip

Heh, yeah I caught that mistake early on. Using a Z80a CPU not the SIO shown in the picture.

On the subject of my not knowing what I'm doing.... for the line stereo output, where is the second channel coming from? Though the YM3012 was a single channel DAC.
 

jammajunk

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Anyone with experience with the legendHK converts? Man, the market has gone to crap; ebay only has bootlegs or super overpriced 'collector grade' boards for 5X the price of what's socially acceptable. I regret not buying more boards back in the days, but I didn't want to be like those pcb hoarders who buy tons of pcbs but never play with them. Ugh.

Sorry for the random rant. If anyone has interest with those legendHK convert jobs, i'm all ears! Are there audio problems?
 

Kujako

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Anyone with experience with the legendHK converts? Man, the market has gone to crap; ebay only has bootlegs or super overpriced 'collector grade' boards for 5X the price of what's socially acceptable. I regret not buying more boards back in the days, but I didn't want to be like those pcb hoarders who buy tons of pcbs but never play with them. Ugh.

Sorry for the random rant. If anyone has interest with those legendHK convert jobs, i'm all ears! Are there audio problems?

Mine had the audio die after about a year, and I've seen similar things from others. I have managed to find a couple good quality CPS-1 "Dash" boards from Mexico, and Guatemala (also low cost MVS carts....). I've given up on China at least for now.
 
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