Gyruss No Sound

Hayate Musashi

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I just acquired a Gyruss arcade cabinet with original Konami board and wire harness, but is has absolutely no sound.

1. I went through the entire cabinet to check for bad wiring. I couldn't find anything wrong.

2. Only one potentiometer on the board and one on the inside of the coin door will produce a hum noise when placed at maximum volume from one speaker. The same potentiometer on the board that produces a hum, when merely touched a static noise can be heard from the one speaker. The other POT produces no hum or static noise.

3. I replaced all the electrolytic capacitors on the sound board with new ones.

4. Installed shoestring's test program. Discovered a bad SRAM chip on 17C. Replaced it with a socket and new 6116 SRAM. All chips were verified and OK by the test program.

After all of this still no sound. I'm thinking it has to be the the LA4460 sound amps or a Z80 problem.

Can anyone assist? Thank you for your time.
 
I just acquired a Gyruss arcade cabinet with original Konami board and wire harness, but is has absolutely no sound.

2. Only one potentiometer on the board and one on the inside of the coin door will produce a hum noise when placed at maximum volume from one speaker. The same potentiometer on the board that produces a hum, when merely touched a static noise can be heard from the one speaker. The other POT produces no hum or static noise.


Can anyone assist? Thank you for your time.

Do you have the mono jumper installed on the audio board ?

Do both speakers work ?

Do you get a buzz/raspy noise coming out of your speakers when you run your fingers across the pins of each amp ?
 
Do you have the mono jumper installed on the audio board ?

Do both speakers work ?

Do you get a buzz/raspy noise coming out of your speakers when you run your fingers across the pins of each amp ?

1. Both speakers work. I tested both using AA batteries. I had to replace one of the speakers because one failed the AA battery test.

2. I do not get a buzz/raspy noise coming out of my speakers when I run my fingers across the pins of each amp.

3. No mono jumper.
 
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With the volume turned up you should hear a buzz noise come through the speaker as you run your fingers across the amp if you're sure that the wiring between the edge connector and speakers via pots [on the coin door] are good.

If you hear nothing at all, then there's a good chance you should replace the amps. But I would also go a step further and check for audio on the inputs and outputs of the two amps first to see if the problem can be isolated to the audio side or the logic [ z80, ram, rom, support logic ..etc ].
 
OK, the possibility of the sound board being defective has been eliminated. I just acquired another Gyruss PCB and swapped sound boards. Sound is fully operational on the first sound board.

The problem is now obviously with the bottom board of my first Gyruss PCB. As far as I know, the bottom board has no sound producing tech at all.

These are the only possibilities I can conjure up.

1. Bad ribbon cable? (I'll swap the ribbon cables and reply with the results)
2. Bad solder joints? (I could not find any and they all appear to be rigid and not loose)
3. Cut traces? (I could not find any)
4. Bad Konami custom IC.

I'll continue to trouble shoot and seek a solution with the bottom board, so any advice would be great because I plan on selling one of the PCBs to cut my losses.
 
You're probably missing power. Do you have 12v and 5v on the top board at the chips ?
 
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Only thing I can think of is that there's a problem with the sound data from the bottom board reaching to the top board.

I assume you've already swapped the ribbon cable ?

If you have a logic probe, I would verify the LS245 @ 1D on the bottom board and go from there.
 
Only thing I can think of is that there's a problem with the sound data from the bottom board reaching to the top board.

I assume you've already swapped the ribbon cable ?

If you have a logic probe, I would verify the LS245 @ 1D on the bottom board and go from there.

1. Ribbon cable has been swapped. No change.
2. I'll try my logic probe on that IC you mentioned in a few days. I'll post my findings if anything changes. This board will have to be "a work in progress" for now.
 
To make it easier, you can check for sound data with you probe directly from the top board at @ 2C ( pins 11 & 13 are D0 & D1 ) and 4C ( pins 9,7,11,5,13,3 are D2-D7 ) .
 
To make it easier, you can check for sound data with you probe directly from the top board at @ 2C ( pins 11 & 13 are D0 & D1 ) and 4C ( pins 9,7,11,5,13,3 are D2-D7 ) .


Quick update. New issue. Upon starting the game with the test ROM installed, I get an error on ROM 8C. I've changed the that chip with both a newly burned EPROM and with one from my working board (labeled GY9 located at 8C) and the same problem persists.

Any thoughts?
 
The problem is actually with 19E Labelled GY5 near the K1 CPU on the bottom board.

Sorry about that, my bad, I'll fix it in the next version. 8C is one of the GFX roms! What was I thinking.

Reseat 19E and also verify that 19E has a checksum of $FEE8 before you do any reprogramming. Then if it checks out fine, check the output enable pin 22 of 19E. 19C provides the output enable signal to this 19E, if it's a Fujitsu part then most likely it has failed. Also check the two buffers at 19F and 19G if the demutiplexer at 19C checks out to be OK.

Edit: Here's the update
 

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I just replaced chips at 19C, 19F and 19G. The 19E error is gone, but still no sound. At this point I give up. This repair is beyond my capabilities. I'll just keep it for spare parts.
 
I just replaced chips at 19C, 19F and 19G. The 19E error is gone, but still no sound. At this point I give up. This repair is beyond my capabilities. I'll just keep it for spare parts.

Replacing those chips does not fix sound, it restored function of the K1 related hardware ( sprites ). So you did actually get somewhere.

You're back to the original issue. Did you check for sound data @ 1D ?
 
I fixed another Konami board recently that was also missing sound. I want to say that there was a "mute" signal coming from the bottom board that kept the top board from producing audio.

Let me look at schematics, I may be totally off on this.
 
OK, found it. Its called "sound on" and it comes from the bottom board. Pin 26 of the ribbon cable.

Maybe its not changing state or the IC that its feeding isnt working. Looks like it basically shuts the sound boards Z80 off so that would make sense.

I suppose you could probe pin 16 of the sound Z80 upon power up, make sure that you have attract sound off then coin it up and see if pin 16 changes state.
 

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I would try what game fixer states but also...
going back to the beginning and work way back. Try a test speaker right at the card edge, no sound, try installing mono jumper to see if you get any sound. (I don't think you will based on your comments thus far but worth doing to be 100%).

I haven't tried this but you should be able to use a test speaker right at the mono jumper to test for amplified sound. My theoretical set up is, + terminal to one jumper pin (each jumper pin represents one channel),- terminal to gnd. If you are getting sound at mono jumper then you know problem is in the amplification section, no sound at mono jumper, problem is with sound generation section.

link to my gyruss sound issue https://forums.arcade-museum.com/showthread.php?t=375939
 
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