Mixers/Consoles - Mackie SR24-4 bad Master noise, Sub Mix is fine

[djclint]

I have a 24 channel mackie mixer with a nasty signal inside the left master and a minor signal in the right master. We tested the lines thru the solo function and all of the levels look gravy. Next we routed out the sub-outs and the sends... no problems there, signal is clean and pure with balanced levels on L/R. I took the bottom off and cleaned out the dust inside, but nothing major was there.

Unfortunately, the inside of the mackie 24-4 is made of three chips: two for the faders/knobs and one for the in/out on back. The power module is separated by some open box of aluminum with major power cables going to the boards right where mackie placed their cheap ribbon cables made of paper! One of the ribbons looks like it got hot while it sat near that power sink... imagine an IDE cable for your hard disc or cd-rom made from super-thin paper and super-thin wire!!!

Any ideas? I will be trying some fader cleaner. The ribbons on this model are soldered on the boards, so any work will be grueling! Thanks, mackie, but I won't be back! I heard your newer boards are made in China... no thanks.

[museav]

Does the noise vary as you move the master faders? If it does then Mackie's are fairly notorious for noise related to the main left and right inserts before the master faders. Inserting and removing a connector in the insert connections several times, or even doing so with some contact cleaner on the connector, will often resolve similar problems.

[avkid]

Consider yourself lucky if it's an old made in America desk.

If the ribbon cable is damaged you can either attempt to have it fixed (probably too expensive to be worth it) or part it out.

[epimetheus]

Does it sound like a motor boat sound? I know, but that's the best I can describe it. I've seen several Mackie's make this kind on noise in the master section, from both the 8-bus and the SR model lines.

[FMEng]

Originally Posted by museav

Does the noise vary as you move the master faders? If it does then Mackie's are fairly notorious for noise related to the main left and right inserts before the master faders. Inserting and removing a connector in the insert connections several times, or even doing so with some contact cleaner on the connector, will often resolve similar problems.

I agree that bus inserts could well be the culprit. Go to Radio Shack and buy a spray can of DeOxit. Spray liberally into the insert jacks and then exercise them by plugging/unplugging a connector many times. If this fixes it, it's nothing more than a little oxidation on the switch contacts. A VERY common electronic problem.

[TimmyP1955]

Dirty "break" switch (the switch that routes the playback inputs to the mains instead of the submasters to the mains).

[djclint]

Originally Posted by museav

Does the noise vary as you move the master faders? If it does then Mackie's are fairly notorious for noise related to the main left and right inserts before the master faders. Inserting and removing a connector in the insert connections several times, or even doing so with some contact cleaner on the connector, will often resolve similar problems.

I sprayed contact cleaner in the master fader with no changes. I did not spray anything in the TRS female ports, if that is what you mean about the connector. I ran various tests on the master, but it seemed like a fader problem... turning the mixer on was occasionally fine until the master was moved.

I took the unit to West End Recordings in Kansas City on 45th and State Line on the recommendation of Electronics Supply Co. on Main St and 41st. The owner found shattered solder with a jewelry lens and repaired them to no avail. We agreed to order a new fader from Mackie, and when he replaced it and went over the other solder points above the fader before testing it and finding that the problem was solved.

It could be, and probably was, the master fader; however, one may never know without testing between that replacement and the other solder points.

Thanks for all who helped. Read on for individual replies on other topics.

[djclint]

Originally Posted by avkid

Consider yourself lucky if it's an old made in America desk.

..and I was told that these are better than the Chinese boards being made today...

Originally Posted by avkid

If the ribbon cable is damaged you can either attempt to have it fixed (probably too expensive to be worth it) or part it out.

The ribbon cable was slightly discolored and physically contorted, but per my previous reply, it ended up not being the ribbon cable. I guess paper ribbon cable doesn't melt like plastic, but it sure seems cheap to use paper over cables in a $1000 mixer. I have updated my mixer wish list and will never buy Mackie after seeing the inside.

Thanks 4 da reply.

[djclint]

Originally Posted by epimetheus

Does it sound like a motor boat sound? I know, but that's the best I can describe it. I've seen several Mackie's make this kind on noise in the master section, from both the 8-bus and the SR model lines.

Quite an interesting comparison, but on reflection it does sound like a motor muffled by water without the bubbling and with a raspy growl... Replacing the master fader solved the problem for now...

[djclint]

Originally Posted by FMEng

I agree that bus inserts could well be the culprit. Go to Radio Shack and buy a spray can of DeOxit. Spray liberally into the insert jacks and then exercise them by plugging/unplugging a connector many times. If this fixes it, it's nothing more than a little oxidation on the switch contacts. A VERY common electronic problem.

This is interesting to me. I got some and used it on the master fader only, but I thought the deoxit would do more for the faders than the connectors... having a full-orange signal that peaks to the red bar at +10db on the left side only and the right side with three green bars with no signal - could that happen on the connectors to cause such havoc?

It went from working fine for a week with nothing plugged/unplugged to having that horrific hum on L side one evening.

Definitely valid advice, but in this case it was prob the master fader.