Gyruss volume pots

Paul Olson

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Does anyone happen to know what pots are used for the volume control at the coin door? The cab only had one in it when I got it, and it is 75ohm. There is not enough range to go from no sound(or even low sound) to nice and loud. I am bringing the game to CAX tomorrow, and I want to make sure there is enough adjustment without having to adjust the pots on the board. Any suggestions?

Thanks,
Paul
 
Someone will have to look at theirs to get the value. I dont think its listed in the manual. I can do it but wont be home until around 8 p.m. tonight.
 
Does anyone happen to know what pots are used for the volume control at the coin door? The cab only had one in it when I got it, and it is 75ohm. There is not enough range to go from no sound(or even low sound) to nice and loud.

The pots at the coin door were only intended for balancing the two channels and making minor volume adjustments. Rather than sweeping the wiper between the + and - signals as a normal volume pot would do, they simply insert a variable resistance from 0 to 75 ohm* into the signal path. Assuming the speaker is 8 ohm, that allows for somewhere in the neighborhood of 20 dB of attenuation.

You could rewire them as regular volume controls - you'd need to make some harness modifications, and keep in mind that you're dealing with speaker-level signals, and I'm too lazy to figure out the pot values you'd need. Another option would be to remove the on-board pots, install similar value pots up front, and run wires from them to the old pot locations on the board. Or, tap the signals at the stereo / mono jumper and use a separate audio amp, putting its controls at the front.

None of those ideas are probably reasonable to implement by tomorrow, so I'd suggest turning the front pots all the way up, adjusting the board to be just a little louder than you want, and then you should be able to trim the sound appropriately with the front pot.

* - yes, I think that is the right value, but I'll be darned if I can find a confirmation of that anywhere. The pots aren't shown on any schematic I can find at the moment.
 
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I never saw the pots listed either. I picked up a 250 Ohm pot at Fry's on the way down to CAX. That is the lowest ohm rating that they had; they just discontinued the 100 Ohm pots. It worked well, and the stereo sound was up minutes after I wheeled the game in the door.

Thanks for the reply.

Paul
 
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