Gyruss Sound Issue

Joined
Dec 28, 2024
Messages
85
Reaction score
31
So I'm diagnosing my Gyruss cabinet. Both amplifier chips were no good so I swapped them out and re-installed the heatsynchs on top using thermal paste. Unfortunately, the issue persists - it has no sound at all. I'm looking for guidance on where I should check next and how to go about checking whether the next piece is good or bad.

A friend said:

"The game uses two Z80 microprocessors, one 6809 microprocessor, and one 8039 microprocessor. For sound it uses five AY38910 PSGs and a DAC."

Wondering if we're on the right track or not.
 
Last edited:
How did you determine that both sound amps were bad, if the board has no sound? Is there any other information you can provide about the board and/or cab? (Have you ever seen this board work? Did it die on you, or did you get it dead?)

Gyruss sound boards have a lot going on on them, so there's no simple answer, if it isn't something simple. But if you're missing all sounds completely, that is different than only missing some, or just having low volume, etc.

I'd start by making sure you know both speakers and the wiring are good. Always start with basics.

Make sure the board has all of the power/voltages it needs. (Is this an original cabinet/wiring? Have you tested voltages? If so, where?)

From there, you could check to see if the sound board has a clock. The schematics are here:


PDF page 32 has the sound board schematics. The clock section is in the upper right. You'll need a logic probe to see what's going on there, however.
 
I made sure the sound wiring is solid because I'll stick in my copy of Time Pilot and sound works perfectly.

I originally bought this pcb off ebay broken and have been progressively making it less shitty as time goes on.

I heard there was an old trick to determine whether sound amp chips are working or dead by turning the sound knobs on the board all the way up and rubbing the bottom of the amplifier chips with your fingers. If they are working you'll hear static/crackling from running your fingers across the bottomside of the chips while the cabinet is on. If not, they are likely dead. The old chips did not make a sound (one did but soon died afterwards). Now that they've been replaced, they do indeed make the sound so I know they were installed correctly and are receiving power. However, I did not use a multimeter to test how much power they are receiving.
 
Why don't you continue your troubleshooting in your original thread, instead of starting a new one?

Did you try any of the other steps I mentioned there?

 
Why don't you continue your troubleshooting in your original thread, instead of starting a new one?

Did you try any of the other steps I mentioned there?

You're right, I am big dumb. Thank you, Time Piloteer. How do I delete this duplicate?
 
Back
Top Bottom