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Taito G-NET — No Sound Issue Solved (But Not How I Expected…)

HardAzRockz

HardAzRockz

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Hey everyone,


I pulled my Taito G-NET system out of storage today and ran into a sound issue I can’t seem to figure out.





Here’s what I’ve done so far:





  • Adjusted the volume potentiometer — no change
  • Recapped both the main system board and ROM PCBs
  • Tested with three different ROM boards and different games
  • Adjusted the 5V line, since I’ve heard these systems can be a bit temperamental about voltage
  • Still getting no sound at all — not even startup hiss or pops







The system was working fine before it went into storage, and this is the first time it’s been powered on in quite a while. The recap went smoothly (no lifted pads, correct polarity throughout), and voltages look good at the power input.





Has anyone run into this before? Is there a common audio amp failure point or muting circuit issue on the G-NET? I’m starting to suspect the amp IC or maybe a mute line stuck high/low after sitting for years.





Any ideas or known fixes would be greatly appreciated!


IMG_2525.jpegIMG_2526.jpegIMG_2527.jpegIMG_2528.jpegIMG_2529.jpeg
 
Hi! :)

Test with the blue switch in the Mono position on the motherboard, to see...
 
Run your finger over the pins of the amplifier IC--it's the IC attached to the big heatsink. Any popping or buzzing? If so your amp is working. If not, probably try to replace it.
 
Hi! :)

Try with that and try change with switch MONO/STEREO and inside the SETUP Configuration MONO/STEREO

20251102_215306.jpg
 
chacal231077 said:
Hi! :)

Try with that and try change with switch MONO/STEREO and inside the SETUP Configuration MONO/STEREO

20251102_215306.jpg
Click to expand...
I’m not seeing any option in the test or service menus. I’m able to configure the sound levels for the game but obviously no sound. I did consider trying to tapping audio from the header. I ordered the same converter you have from Amazon. If you have any other ideas to try please let me know. I ordered some 4558s(op amps) just in case.
 
trashedcabs said:
Run your finger over the pins of the amplifier IC--it's the IC attached to the big heatsink. Any popping or buzzing? If so your amp is working. If not, probably try to replace it.
Click to expand...
Yes, I did notice I wasn’t getting any buzzing or pops. I can’t imagine how it would go bad while in storage. Hopefully it’s either that or the op amps. I’ll order one just in case. Any other ideas?
 
You can easily build an audio probe and follow the audio circuit around to see what is and isn't working...

DIY Audio probe

Can find mine and share a pic shortly.
 
This is mine:

IMG_3334.jpg


Managed to fit the filter capacitor inside a pen as you can see. Pretty easy to probe around with :thumbup:
 
Just wanted to post an update on my Taito G-NET sound issue in case it helps someone down the line.

I originally had no audio at all from my G-NET setup. I went through the entire sound section step by step:





  • Replaced all LA4705 amp ICs
  • Replaced both 4558 op-amps
  • Swapped out the AK4310VM DAC (used in early PS1 units, and since the Taito ZN-2 hardware is based on that platform, I figured it was a reasonable suspect)
  • Removed most of the sound-section components and began mapping the entire audio path
  • Checked traces, caps, resistors — the whole nine yards
After all that… I found nothing wrong. Absolutely nothing.

At that point I was scratching my head, so I tried something different:

Instead of the CBOX Supergun from AliExpress, which I had been using for testing, I grabbed my Mini Supergun that I had in storage.

Plugged it in… and the sound worked perfectly.
View: https://youtu.be/DIeR0Ab3-Zg?si=17LhB3aG-EKiwBkj


So, I’m both happy and angry right now. Happy that the G-NET is fine, but annoyed that the CBOX wasted so much time. What really confuses me is that the CBOX has worked with every other PCB I’ve ever thrown at it — but apparently not the G-NET. Why? I still don’t know. Something about the audio routing or output circuitry on the CBOX must be incompatible with how the G-NET drives its sound lines.

But at the end of the day, swapping superguns fixed the issue.

Posting this in case anybody else with a silent G-NET is tearing their hair out — try a different supergun before going down the rabbit hole like I did.

Hope this helps someone. If anyone knows why the CBOX specifically fails with G-NET audio, I’d love to hear theories.

Oh and thanks @nam9 I did build that audio probe I’m currently using it to diagnose a Namco system 1 with sound issues.
IMG_2750.jpeg
 
Last edited:
HardAzRockz said:
It’s been suggested that the CBOX supergun doesn’t provide a -5V.
Click to expand...
This was my first guess. It's really common for (mostly older) boards to require -5V for audio and modern PSUs don't often offer it (or not enough of it).
 
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