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Primal Rage, Intermittent Audio

plasticfactory

plasticfactory

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Hello, I'm having audio issues with a PR board, that appears to be related to a short somewhere. I'm looking for schematics as following traces for hours has so far been fruitless.

It may not exist, the image attached is all I can find. T-Mek uses the same board I believe, but I am running into the same issues there.

Essentially, I have no audio. The CPU passes its test (LED is lit as well), and ROM Checksums are good. I could push on the DIN 96 connector (ROM expansion connector in the image) and get sound, so I reflowed that part but now I can't manipulate things to get audio at all (though the DIN no longer wiggles). I've ordered a replacement, but doubt it will actually fix the problem. The board itself looks great, and I can't find any faults or damage anywhere.

EDIT: Sometimes I can get audio by wiggling on the DIN that connects the sound board to the main board. Though I'm not getting audio now, and this isn't working, it seems the problem is clearly with this connector.

It is press fit, and I have OEM replacements. Does anyone have any experience replacing press-fit connectors?
 

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Are you just trying to get jamma audio? And is all the normal wiring correct (these two harnesses circled above)?
 
Yes, cables are correct. The audio was intermittent from pushing on connectors, but I can no longer replicate that. Everything is getting proper voltages as well.
 
My board.
 

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I do not have an audio probe.

I'll look closer when I'm back on a computer, but the tmek layout looks very different. The primal rage manual references a quad amp board for some reason.
 
plasticfactory said:
The primal rage manual references a quad amp board for some reason.
Click to expand...
The one in the T-Mek schematic is "quad amp" but I think primal rage is just 2chan. I imagine at least the ICs are similar, since part numbers in the manuals are
A053304-01 (2chan)
A053304-02 (4chan)

Anyway looking at it a little closer, eh, the schematics don't show a whole lot anyway unless I'm missing something.

Since you reworked the connector, it's worth a re-check. Could just be a simple solder bridge somewhere. Did you rework the joints on the main pcb as well as the joints on the audio board? Otherwise I guess I'd start with the boot rom (i think it's 27c1001 but I'll confirm later.. but you can find the pinout i'm sure) to make sure it's enabled and firing, and the TMS (https://pdf1.alldatasheet.com/datasheet-pdf/view/84125/TI/TMS320C31.html) is not in reset. Assuming that's all still good, you can probably assume it's getting input signal and generating the analog signal that was previously heard. If that is the case, it would be helpful to have an audio probe.
 
Thanks for that post, I'll go through your suggestions one by one.

I actually did rework the connector again just to be sure. This connector doesn't actually connect to the main board.

Attached are photos of both connectors. The one that doesn't connect to the main board is the unused expansion port, and is soldered to the sound board. I reworked this twice. I checked for continuity across all pins adjacent to each other, and the very middle 6 pins were all connected, but I assume via traces I can't visually inspect (under the housing) because there is absolutely no bridging on any pins. This is also the connector that when pressed on would give me sound. After reworking that no longer works.

The connector to the main board is press fit. I get continuity from the blue line to the red line, so I assume this isn't the issue.

I can't see or test anything wrong with either connector, but I can't shake the feeling the problem is with one of them. I ordered replacements just in case (I'd like to swap the one with the broken housing, anyway)

Do you have a recommendation for an audio probe? All I can find are DIY options (which is fine, but I'd prefer to just order something).
 

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It’s on my bench now (barely fits...) so maybe I can help. You resoldered JROMBUS in PR_pins1.png? I don't think that goes anywhere, i.e. the problem is elsewhere. Maybe flexing it there was helping connect a trace on the nearby roms, or the clock.

If you flip that switch near the jamma edge it will boot to a test mode. You can go into sound check and confirm the checksum on your audio rom is good. It will also report sound CPU status.

Here's a boot sequence, see if your LEDs do the same thing.
View: https://youtu.be/92iQtHLHv4U


My boot rom is 27c040 https://www.circuits-diy.com/wp-content/uploads/2021/10/27C040-80-Pinout.jpg so you can check those lines if you have a normal logic probe, but doing the self-test should cover you.
 
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Yes, my LEDs do the same thing.

The ROM checksums are all good, and the CPU status shows good.

Yes, JROMBUS is what I resoldered in PR_pins1. I think that header acts as a bridge of sorts. It has traces that go to pins. I tested continuity on all the ones I could see but think there are still traces under the housing.
 
plasticfactory said:
I think that header acts as a bridge of sorts.
Click to expand...
MAME identifies it as a rom expansion which makes sense to me. Some games used headers like this so devs can pop on expansion boards and use cheaper eproms during development. Then they consolidate it all to a larger mask rom for production. Anyway I don't think it would bridge anything, i.e. you could probably remove the header entirely and it would function. However if there's a broken trace or via, or something bridged with solder, that certainly could goof things up.

That said, if your audio rom checksums passed, I don't think there's an issue. If your sound cpu reads OK, that's good too.

Just one more thought - if you switched setups at all during this process, the game does need -5v for sound.
 
That's very interesting. I plugged in an NBA Hangtime and got nothing but noise, and was pretty upset as this is my wife and I's favorite game... Then I realized I had no -5v on the line, and ordered a negatron to make it work.

So... if that's the case, how on earth have I been getting audio from my PR board intermittently? I would have to have -5v, right?

EDIT: I think you may be mistaken on the -5v. From the manual:

1687792524873.png
 
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If that’s the manual yes I’m mistaken. I saw -5v on the mame pinout of the audio board power connector and made the assumption it was being used!

Oh yea actually looking at the pcb now, the -5v pin itself is even depopulated. Sorry!
 
I got really excited for a moment, lol. I did receive my logic probe (and makeshift audio probe as a result), so I should be able to do more troubleshooting tonight. I'm sure I'll have some questions :)
 
@ekorz Alright, dumb question -- where should I hook the logic probe leads to the Primal Rage board?

I'm guessing GND and +5 pins??

1687825580784.png
 
IMG_4470.jpeg


There are ground and 5v test points right on the sound pcb, next to the LEDs. For logic running at 5v that’s right. Set it to TTL if it has a setting (vs cmos).

For an audio probe you’d probably need 12v but I think you just have a regular logic probe right?
 
Ugh... I'm not sure if I should be happy or not. I started testing caps since I got my ESR70, and then hooked up the logic probe to start... Probing. Audio works after turning it on. I've tried gently flexing and pressing to essentially make it go away, but could not. I'm sure it will randomly stop working at an inopportune time, lol.

I have no idea what could have changed.
 
Good times! Maybe power? The board is huge. There are even LEDs on the main board to show you under vs over voltage.

Question about that meter, does it let you test caps in circuit, or are you taking them out?
 
Power has been basically perfect. Measuring the CPU on the sound board was giving me 5.0v.

After jostling it around a bit putting the new case on it I had the sound cut out again. This time I brought it back by pressing on the DIN connector that actually connects the sound board to the main board. I could also get some static when pressing on the power connector. I'm considering just reworking every through hole solder joint when I redo the caps...

The ESR70 lets you test caps in circuit, but I think it either has limitations or I am doing something wrong because I was getting 2000uf on 1000uf caps, and some of them wouldn't read at all. Given the sound is clearly not firing due to some sort of short, I have no reason to believe those caps are actually bad. I plan to recap the sound board anyway, so I'll test them after removal to get an idea of what's going on here.
 
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