Should both L and R channels of a Main Mix Fader be exactly the same resistance readings?

[Clay Pruitt]

So, I finally got the courage to rebuild my almost 25 year old Alesis Studio 32 mixer. After washing the board, and hitting all the switches and faders with either Deoxit or Contact Cleaner, things are actually going better than I feared. The only problem thus far was that only the Right Channel of the Main Mix was working.

After looking at the schematic (I have a full Service Manual), I tracked down the problem with the Left channel to the actual Main Mix Fader (it is, of course, a stereo fader, and so I guess one could look at it in the same general way one would look at a ganged Pot: inside the fader you have two separate sets of graphite strips, and matching lugs, hooked up to those strips, and of course the fader action for both channels is actuated by a single lever. Bring the fader up, and the wiper brings up-or pulls down-the resistance on both channels.)

So, I desoldered the fader from the board, and saw that the Left side was not operating at all. So I took the fader apart, found gunk surrounding a mangled wiper, removed the gunk, rebent the wipers back to their appropriate positions, put the fader back together, and now the Left side is working!

But-there is a slight difference in resistance values between the two sides: at it's two extremes, the Left puts out 15.1 ohms and 1696 ohms, while the Right puts out 12.6 ohms and 1724 ohms. I've never dealt in this way with a stereo fader before so I want to know: is this small discrepancy between either channel in a stereo fader normal?

Should both sides show exactly equal resistance values, or is this small difference in ohms between both channels basically what is happening in all stereo faders? Should I resolder this puppy, or should I hope for the impossible and contact Alesis and ask them if they have any replacement L/R Main Mix faders for the Studio 32?

 

[NOON]

Absolute values are less important than the ratio of the wiper position to the total resistance. E.g. when they're at the halfway position they should both read 50% of their individual total resistance (on a linear fader, a log fader will be a different percentage but same principle) Dual faders and pots are never exactly matched but should be very close throughout their travel. How close depends on the quality of the unit.

 

[Clay Pruitt]

Absolute values are less important than the ratio of the wiper position to the total resistance. E.g. when they're at the halfway position they should both read 50% of their individual total resistance (on a linear fader, a log fader will be a different percentage but same principle) Dual faders and pots are never exactly matched but should be very close throughout their travel. How close depends on the quality of the unit.

Yeah, that makes sense. Thanks for the wisdom!

 

[JohnRoberts]

Probably close enough....

JR

 

[Whoops]

At least at 0dbs position and between -5 and +5 it’s crucial they are very well matched.
At the extremes is as important, they can be a bit of and it’s fine