I have a Midway Stunt Pilot and need to replace the trim pots on the sound board. But I don't know anything about trim pots. What ohm value should I use? Is there anything else I need to consider? I don't see any markings on them to help me out. I do know the board runs off 6 volts. And any idea where to get them? I looked at great plains and mouser and didn't see any that looked like these. Any help would be appreciated. Thanks in advance.