Fixing/cleaning a fader switch yourself?

[u6crash]

I've got a Yamaha MG 12/4 mixer and the fader on the stereo pair 9/10 is really scratchy and tempermental. I've already paid to have this thing fixed once when it died, and I hate to take it in again. I'm broke and I really don't use both stereo pairs simultaneously, but it would be nice if it all worked. Are there some things I can do to fix it myself? I'm not oppossed to opening it up, but I just want to know what I'm getting myself into.

[agedhorse]

The problem with the typical spray in cleaners is that they make a terrible mess inside the board, wash any lubricant off the side-ways, and attracts all kneds of grit and gunk in the future. I would just wait and have it looked at by a service center.

 

Also, if it's making all kinds of scratching noise, it may NOT be a dirty pot but rather a failed component in the signal path causing DC offset to appear across the pot causing this symptom. On as new a console as yours, I would guess this is more likely unless somebody made a previous mess of the fader.

[where02190]

Give it a light spray with Craig De-oxit D-5, and then exercise it for 30 seconds the full length of the throw. If that doesn't fix the problem, and you're comfortable soldering at the PC board level, replace the fader.

[agedhorse]

Very very light spray

[Guest Anonymous]

Originally posted by u6crash I'm not oppossed to opening it up, but I just want to know what I'm getting myself into.

I've never been into one of those yet, but I suspect the bottom 1/2 of the chassis can be removed (maybe). I suspect the outside 4 screws on the back need to be removed, plus the screws along the side/bottom on each side. If you can remove the bottom, hopefully you can gain ready access to that slide pot. If you can fully remove the slide pot as an assembly (unscrew and unsolder it) possibly you can then take some needle nose pliers or small dykes and pry the little tabs up that hold the top and bottom of the slide pot together. Then take a que-tip soaked with isopropal alcohol and swab the spring contactors and black resistor surface. Work the spring contactors back and forth (up and down) while wet with the alcohol. Then take the clean, dry end of the que tip and sop up the dirty alcohol. Repeat if necessary. When finished, lube the spring contactor and resistor surface with a hint of Caig DeoxIt D5S shown here:

 

www.partsexpress.com/pe/showdetl.cfm%3F%26DID%3D7%26Partnumber%3D341-200+Caig+DEOxit&hl=en

 

The Caig stuff lubes as well as cleans, but you only want to use a sniff of it (applied with a que tip). By a sniff: basically show the slide pot a picture of a shadow of an empty can... but get a little on.

 

Reassemble and test drive.

 

Oh... and the plastic knob comes off the slide pot by wiggling (rocking) it top to bottom while lifting up. Don't just pry it off with a butter knife.

 

Credits: I learned most of this stuff from Andy.

[agedhorse]

When faced with an expensive console and lots of faders, it makes sense to clean the parts very carefully rather than replace them. Of course, for the better consoles they use a different more expensive fader style but Marks and my suggestions still apply to the cheaper consoles except that the payback in savings is not so dramatic.

 

For example, I have restored several older PM series consoles to like new condition this way, saving maybe $1000 or more in fader replacement cost. End result, provided the faders were not worn out due to previous spray attempts, is a perfectly functional console with an expected service life of an additional 5 years.