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

uk1simon 3rd March 2012 07:13 AM

I would love to see the fix for this :-(

Pelleman Jensen 11th April 2012 03:56 PM

Unstable power on my 828 Mk2
 
Hi guys,

I live in Sweden and think this forum is just great!
Now I have a problem with my Motu 828 Mk2 that really bothers me. It powers on and off as it pleases, and each time the power goes on the volume is at max! This makes it absolutely impossible to use at the moment, which is very unfortunate since I work part time with some production music for TV....
I've had the LED problem for quite some time as well, but that is at least bearable. However, I'm planning on fixing that according to the exquisite instructions provided by Mr. Yoo! The power instability issue might be harder to fix, though grrr
Anyone with a solution (and maybe similar experiances)?

By the way... In the instructions for fixing the LED you only mention a 3mm HIGH BRIGHTNESS green LED, and I would like to know (not knowing too much about this...) if it's impossible to use a SMD LED instead, or if it's just too expensive? (What type should I use, then?) I'm not too familiar with electronics, thus the stupid question!

LeeYoo 11th April 2012 10:12 PM

Hi.
Not sure about your power problem. I havn't had that one yet.
But I have seen other posts somewhere about failing SMD voltage regulators.
Maybe someone else can chime in on that.
About the LED.
3mm High Brightness green LEDs are easy to find, and easy to mount and solder, even with sausage fingers.
You could use an SMD version, but it would be a lot harder to get that in.
Brightness is really important. I have tried normal LED's, but the display was barely visable.
Leo..

Pelleman Jensen 12th April 2012 08:50 AM

Quote:

Originally Posted by LeeYoo (Post 7769381)
Hi.
Not sure about your power problem. I havn't had that one yet.
But I have seen other posts somewhere about failing SMD voltage regulators.
Maybe someone else can chime in on that.
About the LED.
3mm High Brightness green LEDs are easy to find, and easy to mount and solder, even with sausage fingers.
You could use an SMD version, but it would be a lot harder to get that in.
Brightness is really important. I have tried normal LED's, but the display was barely visable.
Leo..

Thanks for a your reply! I suspected the Voltage Regulator, and hopefully that's where the problem lies. Maybe I can set it as a fixed voltage of 230V instead, since that's what we use in Sweden...?
I'll look at some other posts, if I can find them :)
About mounting a SMD led, I found this page that some might find interesting and helpful!

Using SMD Leds

I'll come back if I stumble upon more problems!

LeeYoo 12th April 2012 09:31 PM

Hi.
Quote:

Originally Posted by Pelleman Jensen (Post 7771005)
Maybe I can set it as a fixed voltage of 230V instead, since that's what we use in Sweden...?

No, with a voltage regulator I mean a small IC on the board that makes a fixed stabilized voltage of say 5volts.
Maybe it was this post...

http://www.motunation.com/forum/view...hp?f=2&t=48230

Leo..

aktech 21st April 2012 01:35 AM

Here it is... almost two years later. I ran into the very same problem on 828mkII, crackling on Mic1 channel only. I was getting LED flicker on Mic1 channel, worse when I rotated the pot, along with scratchy noise if the CueMix control for the channel was up. Didn't find this thread until after getting into the box. Pulled out the mic pot header, resoldered the connections on the Mic1 side just in case of a cold joint but that didn't help. Noise gone when header pulled out, but noise still there in Mic1 channel when header reinstalled. Discovered in this thread LeeYoo's description of double track pot and silverglue problem. I currently have a MOTU TechLink report open and have requested a new mic pot header. Given that the same problem exists with a number of units, as seen in this thread and likely many other forums, they (MOTU) must know about the problem. Hopefully, I'll get the header, but if not, thanks to LeeYoo for the "thingy" tech build instruction.

The other thing I hear in my unit is an intermittent very high-pitched whine, faint, can only hear it if I monitor at high gain in an external mixer (and the noise is NOT in the mixer). I don't know if that noise is just internal clock (or whatever) noise, or a design issue, etc, etc. Anyone else hear that too?

LeeYoo 21st April 2012 02:58 AM

Hi.
I recently took the brave step of taking the pots apart.
Didn't expect it, but it was rather easy.
I unsoldered the pots from the daughter board and straigtened the 4 metal tabs holding the blue pot to the metal bracket.
Once open, I cleaned the inside of the pot with a cotton bud, soaked in contact cleaner.
[Don't touch the very fragile contacts on the shaft side, or spray the whole inside of the pot.]
Haven't put it in yet, because the unit is in use elsewhere.
Will keep you posted.
Leo..

Deleted User 21st April 2012 08:45 AM

I haveing a similar problem with my ultralite. I think its the drivers or its all the motu's.

LeeYoo 21st April 2012 11:51 AM

Is the whining noise changing if you do something on the computer, like move the mouse, or drag a window...

aktech 2nd May 2012 10:43 PM

Pursuant to my post about a week ago, I did receive a reply from MOTU Tech. They do not, as a policy, sell the header board as a replacement part. A field replacement would be so much easier, less costly in both shipping and repair time, less down-time for customers, etc, etc. There is no proprietary circuitry on the board, so the only reason I can figure is that they don't want the hassle of any support calls relevant to installing the header.

Anyway, in regards to resistor values that Lee posted earlier in this thread:
--------------
Get a "header terminal strip" from your local electronics part store.
Jaycar Electronics - Search results HM3212
And some small resistors:
2x 180ohm and 2x1k8 for 75% gain and/or
2x 330ohm and 2x3k3 for 50% gain.
--------------
If I want to run at 80%, is my math correct for 130ohm/1k3, or thereabouts? Also, Lee, did you have any luck with the contact cleaner on the opened pot? Thanks.

LeeYoo 2nd May 2012 11:59 PM

Hi.
Any 1:10 ratio is fine. The values set the gain.
They have to be fairly low to have enough gain.
130ohm/1k3 are good values for medium/high gain.
As for the cleaned pots, they have been put in, but I have no answer yet from the user.
Will keep you updated.
Leo..

Kenman 3rd May 2012 04:05 PM

Thanks Lee !!
 
LeeYoo,

Just wanted to post that I followed your instructions for the cracking sound repair of the MIC inputs and it worked perfectly.

The only thing I did because they had no 180/1.8K resisters was to use 150 and 1.5K ohms instead. I guess that would put the volume closer to 80-90%. Anyway, no more cracks and the MIC inputs work. Thanks for sharing!

Ken
Dallas, TX

LeeYoo 8th June 2012 10:57 PM

Update.
Cleaning the inside of the pots as per post #67 did not help :(
The crackling came back after a few days.
Leo

macproaudio 10th June 2012 06:56 PM

Hi LeeYoo,

Not sure if I understand correctly, the fix you mentioned in 'post 16' , does that fix the crackling sound on the mic inputs permanently?

Mac

LeeYoo 11th June 2012 12:23 AM

Hi macproaudio.
Yes.
The cause of the crackling is the gain pots.
If you replace the pots with resistors, you get a working pre again, but with a fixed gain.
The gain depends on the resistor values.
Leo..

macproaudio 12th June 2012 04:02 PM

Quote:

Originally Posted by LeeYoo (Post 7964770)
Hi macproaudio.
Yes.
The cause of the crackling is the gain pots.
If you replace the pots with resistors, you get a working pre again, but with a fixed gain.
The gain depends on the resistor values.
Leo..

Are you still sending out those 'resistor kits'? , really appreciate it , let me know and I'll private message you my address. I'm terrible with electronics and this crackling is getting really annoying now, can't record anything.hjghfgg

Mac

hard_core 3rd August 2012 01:46 AM

Quote:

Originally Posted by WEVEW (Post 6119678)
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..

Dear Leeyoo,

Many thanks for your clear explanation regarding the replacement of the backlite LED of the MOTU 828 MKII.
Based on your description, I was been able to replace the defective backlite LED.
I've made a picture document of the repair actions, which I like to share on the forum. (Repair defective backlite Motu 828 MKII 02.doc)

I've tried to upload it, but am not sure I succeeded.

Best,

Erik

Thank you so much for this fix!! Only took me 20 minutes and now I dont have to buy a new soundcard! cooge

LostTribes 2nd January 2013 08:05 PM

I have the same problem. The unit was fine before but I started to notice it.

The led for mic 2 blinks even when the gain is down and I can hear crackles and pops on my recordings.

I was playing around with the clock source on the MOTU Audio Setup program and changed the clock source to 'built in output' on my mac and the problem disappears.

I know this external clocking isnt ideal but might help some people.

Not sure also if this eliminates the possibility that my problem is related with the gain pot?

rimer 25th January 2013 07:48 PM

First of all thanks to LeeYoo & Erik for the clear guide, having to open my secondary 828 anyway because some power caps were busted, I was able to fix the led and it works perfectly.

What are your thoughts on how bright the led actually should be to approximate the original?
Now I went for a 150 mcd, which were rated as high-brightness, but it is rather dim compared to the original unit..
I guess I'll try something ten times that, those are rated ultra-bright at my store actually.

LeeYoo 26th January 2013 11:30 AM

Hi rimer.
I used a 6500mcd 3mm green LED with a clear lens.
This gives a bright display.
A normal green plastic LED was too dim.
Leo..

JJAM 18th February 2013 09:39 PM

Hi LeeYoo, I am also experiencing the mic pre crackling problem which is driving me mad. Do let me know if you are still sending out these resistor kits too! Your advice is much appreciated.

LeeYoo 19th February 2013 08:30 PM

Hi JJAM.
Sorry, I don't have anymore.
I did google "electronic parts in Londen" and came up with this site.
PCB Interconnects
You can make a lot of them with a 36-way straight CN103 header.
Break this in 4-pin parts.
Use 1% metal film resistors like these.
Metal Film Resistors - Bitsbox
Order e.g.
2x100ohm/2x1kohm
2x180ohm/2x1k8
2x330ohm/2x3k3
Solder the resistors to the short part of the pinheader.
Low value to pin 1 and 3, high value to pin 2 and 4.
Use as explained in previous posts.
Leo..

jayer 13th June 2013 12:48 AM

motu 828 mkII pontentiometer
 
Hi Leeyo

I was wondering if I can use a preset pontentiometer to
do what you suggested on the word doc?
It was suggested to use a 4 pin strip and some ohm resistors.
Also with the ohm resistors what spec do they need to be.

100 Ohm to 300 Ohm Metal Film 0.6W Resistors : Metal Film : Maplin Electronics

on the maplins link above it is speced as o.6w. is this info important? or can I just buy based on the 100ohm spec?

Thanking you

Jayer

LeeYoo 13th June 2013 03:56 AM

Hi jayer.
Those metal film resistors are perfect.
You can find a picture of how to in post#41.
I suppose you could also use two (tracking) trimpots per channel.
But the resistor ratio should always be 1:10. A bit hard to do I think.
Another option would be DIP switches with various fixed resistors.
A perfect solution would be a multi step front panel switch with fixed resistors, but there is not much room for that on the front panel.
Leo..

jayer 13th June 2013 02:51 PM

Thanks Leeyoo

I took the motu apart via this thread and it looks so easy to just replace the daughter board.Shame motu don't make a replica or a like for like part.

Such an easy thing to solve.but yet so delicate to fix.

Thanks again,you have transformed many live of motu 828 users.

Jayer

jayer 13th June 2013 03:02 PM

motu 828 mkII driver bleeps and squeeks(not related to mic pre pots)
 
Ps for anyone having problems
with the drivers and squeeks and bleeps. I have found that imaging your system on to a new hard drive gets rid of the random squeeks.

Having looked into this for 6 years,it seems that if your hard drive is not de fragmented properly or if the hard drive size is small,lets say below 300gb
then at some point you will get the squeeks and bleeps.
This is because you can easily fill up 300gb within 6 months and when the system has not space to run,lets say below 30gb then these problems will start.
Also if you leave stuff all over your desktop and let that build up then the squeeks and bleeps get worse because I guess the hard drive cant keep up with the demand of data going to the fire wire motu and operate your system efficiently.
I don't get any more squeeks and bleeps and I stay on top of defragging right from the beginning.Always keep a back up image of your system.Because reformatting and reinstalling from scratch is a big time consuming pain. Having done all of this my system has been stable for 3-4 years running two motu 828 mkII on win xp SP3

Hope this will help some one out there.


Jayer

Zinalias 19th June 2013 11:18 AM

Quote:

Originally Posted by LeeYoo (Post 5538314)
thumbsup

Hi Lee Yoo, thanks for sharing this much, really appreciate.
i have the exact same problem with this noise, it started with preamp 1, then continued to pre2 also. also mute the channels in the Cuemix and i dont ear the noise, but the noise is recorded (cause the mute is only for monitoring right?) and thats the main problem of course, the other annoying thing is than the noise seems to leak into the other channels, not in the monitoring but in the recording. i mean, when the noise comes up only the meters of pre's 1 and/or 2 turns on, but while recording if the noise shows up it prints in any channel i may use. so as far from now i cant use the motu for recording cause the noise is now showing up at least once in a minute or more.
So, wich one of the 2 solutions you posted can you recommend me for this, DIY1 or 2?
thanks again!

LeeYoo 19th June 2013 12:04 PM

Hi Zinalias.
Have you already tried using the unit with a removed daughterboard.
There should be no crackling noises then.
As said in previous posts, the easy way out is two pinstrips with fixed resistors.
The only drawback is that the mic gain is also fixed.
If you want some sort of gain control, you have to find a way to change those resistor values.
Leo..

steenamaroo 24th June 2013 05:01 PM

Glad this thread is still active - I've had the crackling pot issue for a long time.

I also decided to open and clean my crackly pot this week.

I've tested it for about an hour with frequent gain changes and it has been fine.
It's a little noisy as I turn it, but perfect when set.......so far.

Unlike LeeYoo, I slightly raised the fragile wipers, and cleaned their contact points, as well as cleaning the traces.

Hope that's useful to someone.

LeeYoo 24th June 2013 08:52 PM

Hi steenamaroo.
IMHO, the wipers are not the problem.
As said before, I think the problem is the lack of space between the two carbon tracks.
Sometimes you can even measure resistance BETWEEN the tracks.
A simple clean did not last in my case, but you might be more lucky.
Keep us posted.

Still waiting for somebody to post a detailed mod to re-route that Vref.
That would solve all these problems, and restore the faith in MOTO again.
Leo..