MOTUnation.com

Wanted to re-open this old post, because I found a fix for Motu 828 Mk 2 physical transformer hum that I hadn't seen anywhere else.

I had a unit that worked OK for many years, then suddenly developed an annoying physical hum. OK if it was in a rack somewhere, but very annoying when I moved it under my iMac, right 18" from my head.

I opened the unit, tightened/loosened the transformer screws, tried to squeeze glue into the transformers etc, nothing worked.

Then I spotted that C205 - a capacitor near the transformers - looked wonky and appeared to have leaked some fluid. It's a 330uf 63v Electrolytic capacitor.

I replaced that capacitor (it was pretty fiddly to desolder the old one, I ended up soldering the ground wire directly to the PCB trace) and immediately the hum is dramatically reduced.

[YouTube]http://www.youtube.com/watch?v=zVey-8ROmZY[/YouTube]

Thank you for that - I will try one of these days. Can I ask - when you opened it - did it seem the hum was from capacitor or from transformer?

(or maybe I should get another one - now the backlight for the LCD display is gone as well)

The buzz seemed to be from the transformer.

I just de-soldered and re-soldered the transformer in my motu 828 mk2. No noise at all now. None. It buzzed so much previously that it just put me off using it at all.

All I did was to pull the transformer away from the main board while de-soldering and resoldering the joints. It now sits about 1mm above the board and I repeat - there is no noise at all!

I dont know if re-soldering capacitor c205 was anything to do with it but one of the joints looked a bit dry so I re-soldered it anyway.

I am going to try the same thing on my 1224 next (slight buzz but nowhere near as bad as the 828 was.

My 828mkII sits approximately 18 inches from my face. Until reading this thread, I never noticed a hum or a buzz. After reading this thread I stood up and put my ear against the top of the case.

There is a slight buzz.

Sonufagun, mine does, too.

I checked my other rack gear. The MTP AV does not. Almost everything else does.

My 828mkII is the most noticeable rack mount as I can detect it from about 10" away if I know what to listen for. I do now...

Not as loud as my Mac or HDs, however.

Got my 828MK2 this summer back from MOTU repaired for bad input. Finally sat down tonight to do some work and the thing buzzes like crazy. Do they not check this stuff out when it leaves the repair facility? I have a serious project coming and more down time! I should have checked this out when I got it back. I am gong to try the fixes. Any other ideas?

Started on the fix. Thanks MOTU for the stripped screw in the chassis.

Off to get a screw extractor.

All is quiet now. Took the unit to where I teach and the electronics repairman and I took it apart. We had to drill out the stripped screw. His remark was who the... torqued these screws down. Upon opening it was apparent what was buzzing. The shielding around one of the transformers was vibrating. The fix was a plastic toothpick inserted between the windings and the shield. Worked like charm. It is 12 inches from my head and I can not her it. Here is a link to a pic of the fix.
http://www.davidosuna.com/html&swf/828fix.html

Thank you for the picture. My unit's buzzing more subtle nevertheless definitely audible. Will try toothpick next time I open it up.

Old thread but what the heck . . . I've had my 828 mkii for over a decade. It's always had a slight tolerable buzz/humm, but a few days ago it suddenly became much worse and intolerable. Great to see so many have had some success in curing the problem. I'll probably dig into it this weekend to see if I can fix it.

buenavista wrote:Old thread but what the heck . . . I've had my 828 mkii for over a decade. It's always had a slight tolerable buzz/humm, but a few days ago it suddenly became much worse and intolerable. Great to see so many have had some success in curing the problem. I'll probably dig into it this weekend to see if I can fix it.

Sent from my iPhone using Tapatalk

Apparently it needs the words .


Sent from my iPhone using Tapatalk

I used google and found this at the top of the heap.

http://cdn-data.motu.com/manuals/firewi ... al_Mac.pdf

tombola wrote:Wanted to re-open this old post, because I found a fix for Motu 828 Mk 2 physical transformer hum that I hadn't seen anywhere else.

I had a unit that worked OK for many years, then suddenly developed an annoying physical hum. OK if it was in a rack somewhere, but very annoying when I moved it under my iMac, right 18" from my head.

I opened the unit, tightened/loosened the transformer screws, tried to squeeze glue into the transformers etc, nothing worked.

Then I spotted that C205 - a capacitor near the transformers - looked wonky and appeared to have leaked some fluid. It's a 330uf 63v Electrolytic capacitor.

I replaced that capacitor (it was pretty fiddly to desolder the old one, I ended up soldering the ground wire directly to the PCB trace) and immediately the hum is dramatically reduced.

[YouTube]http://www.youtube.com/watch?v=zVey-8ROmZY[/YouTube]

I finally dug into my 828mkii. I had three swollen caps, including c205 that tombola mentions. Replaced them all, and got the same results as tombola--dramatically reduced humm. Before the replacement the humm was intolerable, now it is hardly noticeable. I actually just ordered an an original traveler (bus powered or wal-wart)to replace the 828. Hoping for the same sound with absolutely zero noise.