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-   -   MOTU 828 mkII USB crackle (https://www.gearslutz.com/board/music-computers/449416-motu-828-mkii-usb-crackle.html)

p.pan 30th January 2015 06:38 AM

Hi,

I receive a 828MKII refurb from Motu 2 years ago.
The machine was looking very nice like new......BUT she stop and start randomly.

Meaning I switch on the motu and after hours she stop and restart......
Impossible to work with....
I put the 828 away.

In the same time I dont think its a big things.
I try to have info to be able to repair it.

Any help are welcome.

LeeYoo 30th January 2015 07:06 AM

Hi p.pan
From memory, the 3.3volt regulator IC could have dry-joints on one of the pins.
The regulator looks like a transistor, and lies flat on the main board.
Located near one of the transformers. I think LM117-3.3 is printed next to it.
All from memory and pictures, because I don't have the unit here.
Try reflowing the pins with fresh solder first.
You will need a temp controlled iron and some experience....
Get help if you don't have these skills.
Leo..

p.pan 30th January 2015 08:49 AM

Thanks a MILLION LeeYoo.

I am not a technician but I will find one here where I live, and give him the indication.

Again......I am impress because on Motunation nobody give me infos.

kfhkh

6strings 30th January 2015 03:20 PM

Quote:

Originally Posted by LeeYoo (Post 10773258)
Hi 6strings.
The power rating of the resistors is not important. 1/4watt is perfect.
Best to use metal film resistors for lowest noise.
Pinstrips are VERY common, and are used on almost every circuit board.
RS has sooo many listed that it's hard to find a plain one.
You must be able to get them in your local electronics store.
Schmartboard Qty. 10.3 Jumpers and 40 Headers : Jumpers & Headers | RadioShack.com
Break-away 0.1 36-pin strip male header (10 pieces) ID: 392 - $4.95 : Adafruit Industries, Unique & fun DIY electronics and kits
Leo..

Hi LeeYoo,

Thanks for the info! kfhkh

Cheers,

JP

Otium 9th September 2015 07:25 PM

Quote:

Originally Posted by LeeYoo (Post 6158283)
I saw in another thread that some people also had problems with mechanical buzzing noise inside the unit. This was also a problem in our unit.
This is how I fixed it. Sorry Erik, stole part of your picture for that.
Leo..

Hi LeeYoo!
First off: thank you for your effort and all the good information you are sharing! You should get paid by Motu for that. kfhkh

I also have that mechanical buzzing noise coming from the transformers. But when I open your .doc file on my computer, the "dots" where to put the glue don't seem to be in the right place. So could you maybe upload a pdf version or describe where to put it exactly?
And is there any risk of damaging the unit or the transformers with that glue? I do have basic soldering skills, so I think I should be able to do that.

Thanks!
Alex

vogltek 26th September 2015 01:05 PM

same here, same here.
 
Like many others I have that Mic 1 Crackling-Sh** (pardon my french) as well.

Im able to fix minor damages like soldering Faders and so on, but my rechnical/repair skills aren´t good enough to fully understand YeeLoos fix.

Maybe I could do it, but my mother tongue is German, my English is good, but its another thing to understand technical instructions and technical vocabulary.

Unfortunately YeeLoo isnt answering my PM, the post is rather old, so I wanted to ask if anybody else could

->prefix YeeLoos solution and send it to Austria.
(for sure incurred costs will be covered in advance)

->or translate the solution in detail to German.
(Even if I cannot do it with a German solution, I could explain it to a
e-engineer-friend)

Would be very nice, need my Mic 1 back;-)

PS: Is it really impossible to get this special poti, even searched worldwide?

Tronographic 5th December 2015 05:06 PM

Hey Starbearer, since BLA no longer services the 828 MKII, do you think you could share with us a little more info detailing this modification. like maybe a few pictures or just a few more clarifications. I'm about to tear into my MKii to fix the LED and I would like to address this issue as well. - THANKS!

Alternately, has anybody else here performed this mod and can you post some more details?

Also, I'm not sure you guys saw this or if it was posted in this thread but this guy here has a slightly more elegant solution to the LED fix:

How to fix the display backlight of the MOTU 828 mkII | niek.be

Quote:

Originally Posted by starbearer (Post 6368034)
I just simply rerouted the v-ref voltage further up the signal chain so that it's not going through the dirty pot. This eliminates the v-ref voltage from sporadically changing due to the weakened stability of the pot. Motu is the ONLY interface company who i've seen who routes the v-ref through a pot. That is just stupid.

you don't need to replace the pots. just take out the resistors that feed the v-ref to the 2134's and put new isolating 10k (at least 10k) resistors on the other side of the 47k resistor network or solder them straight to the input pins of the next buffer stage. but then you take some ultra fine hook up wire and hook up the v-ref voltage to those resistors.


Bob4u 9th November 2016 02:29 PM

It's well known that MOTU 828 MKII have defective MIC/GUITAR inputs causing very annoying and unpredictable noises and crackles, even with sensitivity TRIM set to minimum.
To proof it just *disable* completely MIC/GUITAR inputs and see if noises disappear.
The cause is in two potentiometers with defective terminals (not the usual wiper problem of pots).
Unfortunately they are IMPOSSIBLE to find in the market.

In this tutorial I will explain how to build compatible potentiometer, even on the mechanical point of view, and fit the problem spending only about 10 $ !!

Enjoy!


caotico 23rd November 2016 06:24 PM

Quote:

Originally Posted by Bob4u (Post 12244771)
It's well known that MOTU 828 MKII have defective MIC/GUITAR inputs causing very annoying and unpredictable noises and crackles, even with sensitivity TRIM set to minimum.
To proof it just *disable* completely MIC/GUITAR inputs and see if noises disappear.
The cause is in two potentiometers with defective terminals (not the usual wiper problem of pots).
Unfortunately they are IMPOSSIBLE to find in the market.

In this tutorial I will explain how to build compatible potentiometer, even on the mechanical point of view, and fit the problem spending only about 10 $ !!

Enjoy!


Thanks. Impressive.

wakestyle 24th November 2016 05:38 AM

Generally, people make the mistake of thinking they can use a interface like this to play large amounts of VI's at near-realtime latencies, and you can't. You have to use Direct Monitoring routing then all will be good.
Use offline rendering, etc.

Dan Williams 27th February 2017 04:59 AM

Bad op-amps. MOTU uses cheapo 1458 op-amps and after a while they develop popcorn noise. has happened to two of mine. replace the mic inputs with AD8599, the other inputs with OPA2134 and outputs with NE5532. Change to the sound is amazing and the popcorn noise is gone.

steenamaroo 6th October 2017 12:26 PM

Hello again folks,
Old thread, I know, but I thought I'd revive it as I've decided to replace my potentiometers with a view to selling my 828mk2.
I will disclose and describe the fix, of course....but that's not why I'm here.

I ordered dual potentiometers of 2k2+20k rev log (twin waver) from omeg.co.uk

My intention is to mount them on the faceplate and do away with the daughter board completely.
That requires drilling/filing out the faceplate hole to 7mm for the pot bush and also requires using different pot caps (4mm shaft) so while this may not be a like for like transplant in that respect, it is still a solution of sorts.

That said, 6mm shafts were available, as are different lengths, but the bushes would then have been larger...I just chose to go this way but shop around - Maybe you'll find an even better option!

While voltage on a pot may not be ideal, if the original issue was caused by crosstalk between the tracks I suppose separate wafers should solve it, long term.

Minimum order was £25 which, with postage and tax, would have got me three pots.

Being that they are used in pairs I opted to buy four and, as such will have two available if anyone wants to buy them.
Happy to show my final receipt - There's no attempt to profit here.

I'll post back here with confirmation that everything's OK when the jobs done, and add some pics too. :)

steenamaroo 6th October 2017 01:27 PM

3 Attachment(s)
Well, job done and everything is perfect.
It's neater than it looks, I assure you. ;)

If anyone would like my spare pair, please give me a shout.
Thank you Margaret @ Potentiometer switch manufacturer, Omeg for your help.

Edit : My alternative pot-caps are in the mail.

steenamaroo 14th November 2017 07:34 PM

1 Attachment(s)
Pot caps fitted - Everything's good.
Still have the pair of spare pots if anyone's interested.

rasseru 15th November 2017 02:06 AM

I have this problem. How do you disable the mic inputs?

Mine is creating a weird change in pitch (almost like sample rate changing) so I don't know if it's the same thing.

Tried turning the volume down on inputs and it didn't seem to do anything

steenamaroo 25th November 2017 02:49 PM

Quote:

Originally Posted by rasseru (Post 12959246)
I have this problem.

Doesn't sound like that's the case.
Maybe you should slave to a different clock for troubleshooting?

cake100 28th November 2017 05:19 PM

Someone is selling one near me for around $140 US. I took a look at it and the screen seemed a little dim.
Looking through this thread and the reports about the crackling, etc., is this worth buying?

steenamaroo 1st December 2017 06:59 PM

Did you see it in person? LED screen often appear dim in photographs.
If it was dim IRL maybe he added the current limiting resistor or replaced the LED at some point?
Worth asking but not really a big deal.

Regarding the pots, I would consider them a time bomb. If you're going to buy, do so assuming that they will go crackly some day. It's the only way not to be disappointed.

Personally I just used outboard pres and ignored built-in 1+2.
The only reason I sourced a better repair solution was because I didn't want to take a big hit on resale value.

If you're capable of the fixed resistor mod detailed in this thread and wouldn't care too much about having fixed gain then it's always there as an option.
If not, my solution is great although, as I described, pot mounting differs from the original way.

FlashHercules 1st June 2018 09:53 PM

Can someone point me into the direction of these pots, link perhaps? I have a used 828 MKII on the way with a crackle on Mic 1, and would like to do this mod as well.

tophatelec 9th June 2018 12:37 AM

Hi all, the Vref mod to remove the DC offset from going through the gain pots and causing the crackles is as follows in the diagrams.

Firstly remove the 4 x SMD resistors shown in red ( 2 per channel) to isolate the DC from where it is unwanted.

Then connect 4 x 10k resistors (2 per channel) between the Vref nodes (shown in blue) and each of the inputs to the following stage (shown in magenta)

Obviously the Vref line is common to one side of each new resistor, but the other side of each resistor connects in 4 different places due to there being 4 signal inputs.

I have tried to make the diagrams as clear as possible but use care during the mod, because of lack of space to mount the new components. It is neater to make use of the through-plating in the various locations to solder the resistors, rather than the SMD pads, carefully scrape these to bare copper and then feed the leg of the resistor through the existing hole in the PCB. Where the two resistors need to be connected together common to Vref, they can simply be soldered to each other rather than separately onto the board.

The other common mods have also been done to this unit, blue backlight for the LCD and various other general servicing.

Good luck

Image 1
Image 2
Image 3
Image 4

steenamaroo 24th June 2018 06:40 PM

Quote:

Originally Posted by FlashHercules (Post 13348818)
Can someone point me into the direction of these pots, link perhaps? I have a used 828 MKII on the way with a crackle on Mic 1, and would like to do this mod as well.

Replied to your PM.
I still have my spare pair; All the details are a few posts above.

JosMeulman 20th August 2018 10:44 AM

Quote:

Originally Posted by steenamaroo (Post 12889436)
Well, job done and everything is perfect.
It's neater than it looks, I assure you. ;)

If anyone would like my spare pair, please give me a shout.
Thank you Margaret @ Potentiometer switch manufacturer, Omeg for your help.

Edit : My alternative pot-caps are in the mail.

How can I get the pots and a discripton how to do (motu 828MKII)?

JosMeulman 20th August 2018 01:36 PM

Quote:

Originally Posted by steenamaroo (Post 12889436)
Well, job done and everything is perfect.
It's neater than it looks, I assure you. ;)

If anyone would like my spare pair, please give me a shout.
Thank you Margaret @ Potentiometer switch manufacturer, Omeg for your help.

Edit : My alternative pot-caps are in the mail.

I think I have the same problem with my Motu 828mkII
How can I get the parts en the discription how to solve the potmeter problem.
Sorry for my englisch.
Gr Jos Meulman, The Netherlands

esox_13 8th January 2019 06:04 PM

What do you think about that :

RK14K Series - Basic information

Upload 25th May 2019 01:39 PM

Downgrade solution
 
Hello everyone,

For disable cracks (software generation) in MOTU 828 Firewire, the coolest solution is downgrading drivers with this one :

https://ufile.io/qe6iqkmw

I Known is working in Windows 10

bumpkinbumpkinbumpkin

MFSAKA 30th June 2019 03:35 AM

Hi!
Got my Motu 828 mk2 usb audio interface run on my PC. Win 10 Pro x64 1903. Try all drivers versions for MOTU but
from time to time the sound completely disappears. Before this happens, there is a strange high-frequency squeak or short sound. Sometimes she switches to 48 kHz.

Another strange thing that i have COMPLETELY NO SOUND if i set my latency to 128


The hardware of the device is normal, diagnostics were performed, there are no problems. The device is powered via a UPS with a voltage regulator. I connected different cables to different ports of USB.

In the "Energy Saving Schemes" power off USB is prohibited.

Try different settings combinations in MOTU audio console software.
Try to reset defaults on device.

Nothing helps. Help to deal with this problem.

Specs:
AMD FX8320
ASUS SABERTOOTH 990FX R 1.0 MB
NVIDIA GEFORCE 560 SE
8 GB Ram

Samsung SSD
WD RE 1 TB HDD

PC Seasonic 1000W 80 plus
USB Logitech Mouse and Hator Gaming Mechanical keyboard


Today i test MOTU on diffirent computer so i'm sure that not my PC hardware issue!
Please help

PeterWoodx 28th December 2019 01:28 PM

Quote:

Originally Posted by LeeYoo (Post 5212187)
This post if for you slutz, who want to replace the backlight themselves.

Don't start this if you haven't got some technical and soldering skills.

Remove the front panel from the unit. Don't forget the little srews next to the mic sockets and a nasty hook on the circuit board that locks the two boards together. Unplug the two plugs from the MAIN BOARD, not from the front. This plug has got less pins than holes, so you could make a mistake here, plugging it in again (like I did). Work on a clean surface, to prevent dust building up behind the perspex front. Remove the display (note that one screw has a plastic washer). Remove the solder on the two contacts, next to the display with a solder sucker, or with solder litze. Break away the very small strip with the smd led on it, by pulling on the desoldered wires. This is glued onto the side of a perspex sheet, that runs under the display. Buy a 3mm HIGH BRIGHTNESS green LED from your local electronics store. The green means the light, not the colour of the plastic. It should set you back close to US$5.00 , don't use a normal one. Cut off the shortest leg to 10-12mm (half an inch) and bend it 90 degrees. Tack this short leg to the bottom contact, making shure, the front of the led shines into the middle hole (indent) of the perspex plate under the display. You can see this by lifting the tin foil a bit. If it fits, cut off the other leg and solder it to the top contact. Stick a piece of black tape over the led to prevent the light bleeding into the neighbouring display. Assemble in reverse order.
Post your findings..

Thank you so much for this guidance. I just replaced the faulty LED on my MOTU 828 Mk2 with your help!kfhkh