Avid Artist Mix not powering up

[pucho812]

hard to say without a schematic,
normally with the test points you can isolate what part of the circuit is not working correctly.

 

[scott2000]

What's up with all that flux in the area around around U13 (and U13 looks weird....maybe picture focus)..??? Is that a burn mark on U37???


That entire area looks messy for sure...Not saying it's anything but, sure is messy....solder splashes...etc

 

[sonolink]

hard to say without a schematic

I can imagine... problem is I can't find one 

What's up with all that flux in the area around around U13 (and U13 looks weird....maybe picture focus)..??? Is that a burn mark on U37???

Thanks for your post Scott. The board has quite a few flux splashes but it came with those. Not my work.

Here's a closer view:
https://drive.google.com/file/d/16-bPv17Kh331RH-IF4AZ09mAbrZiSNTh/view?usp=drivesdk

https://drive.google.com/file/d/16-7FQiD25SVR_pWYCERL2mJLdsamMero/view?usp=drivesdk

Cheers
Sono

 

[scott2000]

I tried reflowing L7 and L8 and nothing has changed

After reading your link on this, it seems that replacement of L7 was necessary in some cases....this was said to work and is in the newer Artist Mix..... ICM2824ER301V  (of course it's obsolete from what I can tell...have to find a suitable replacement)

https://www.mouser.com/Search/Refine?FS=TRUE&N=1525883+4292906361

. One person even removed / bypassed it

I have noticed that the unit actually POWERS UP. If I plug the PSU and press Power, I can read voltages at some testpoints AND there's 2 diodes marked D1 and D2 that light up. You can't see that without the unit open. When pressing Power again to switch the unit off the diodes won't light off. I have to unplug it for that.

And how does the working unit act or compare to these observations??

 

[sonolink]

Well I never got to comparing it because someone is trying it to see if he wants to buy it. The problem arouse when I decided to sell both units. That's when I switched them back on. I'll ask him to bring it back and compare

 

[scott2000]

Judging from online....seems that choke is a common failure

 

[sonolink]

Choke would be L7 and L8?
I tried reflowing them but it's not easy with an iron and I'm afraid of using the hot gun. After reflowing nothing changed.
If it's L7 and L8 I'll have to replace them with the component indicated by the Avid guy on that thread I guess

 

[scott2000]

Yes... I mentioned the (obsolete?) part above .... Still be interesting to hear how this fault could affect the rest of the circuit the way it is.....

..... of course it could be  a different issue altogether....

 

[Khron]

Any photos with the suspected choke and the circuitry around it? I'm somewhat curious about its role...

 

[scott2000]

First post has the pic of entire board. Top left  where power comes in. L7.... I guess it's for emi suppression or something...??

 

[Khron]

Makes a person wonder just how that fails there. Do these units really need that much "juice"?

Well, on second thought, they might, when all the faders are moving, i guess... But still, that looks like some chunky wire on those chokes.

Regardless, at least for testing / sanity-checking, you could bypass the two sides of that choke with some not-entirely-flimsy wires. Just measure first and make sure you don't end up soldering the wires the wrong way around.

 

[sonolink]

Regardless, at least for testing / sanity-checking, you could bypass the two sides of that choke with some not-entirely-flimsy wires. Just measure first and make sure you don't end up soldering the wires the wrong way around.

Sorry I don't understand what you mean.... you're talking about the red wires attached to the faders?

Cheers
Sono

 

[Khron]

That choke is (and is used as) this:

https://www.murata.com/-/media/webrenewal/products/emiconfun/emc/2014/10/1410_emc_en28_1.ashx?h=268&w=482&la=en-gb

https://en.wikipedia.org/wiki/Choke_(electronics)#Common-mode_choke

One side is in series with the "positive" end of the incoming supply, and the other side is in series with the "ground".

For testing purposes, i was thinking of bypassing the two sides with some relatively substantial wires (while we're not worried about noise "details", but rather the functioning of the unit overall).

[Later edit]

Taking a (closer) look at the datasheet - i can't help wondering how a common-mode choke rated for 5A(!!!) allegedly "failed".
I see the unit's supposed to be powered with 15V - that would mean >65W would've had to be circulating through that choke.

... Unless the power supply's been spewing out so much ripple, that it somehow affected the core, or...?

 

[sonolink]

Oh I understand now!! At least the idea. It's like an equaliser really, well more like a filter!

So if I understand well this, L7 and L8 have 4 terminals each (2 inputs (+ and -) and 2 outputs (+ and -).

If they are the element that fail, bypassing them would reveal that. So I should short L7 positive input yo it's positive output and same with the negative side, correct?

A couple of questions:

- do I have to desolder and take out L7 or just bypassing it would do?

- Why are there 2 chokes (L7 and L8). To filter different frequencies?

Thanks a lot for your time Khron!

Cheers
Sono

 

[Khron]

L7 is connected to the DC input. Isn't L8 connected to the 1/4" jack terminals?

PS: Upon closer inspection, i see those two factory chokes are not the beefy Wurth ones (ICM2824). Which means my previous comment about that should be disregarded  :-[

Those "monolithic" ceramic ones may well be only marginal in their current-carrying capability.

That yellow through-hole part is most likely a PTC / polyfuse, very likely in series with the DC input.

What component is U3D? SOIC-16 package, just "south" of the big fat D127 diode.

 

[sonolink]

I did read your link. I just assumed both windings were built in L7.
L8 can be found to the right of L7 on the other side of the DC connector.

If L7 and L8 are 2 halves I don't understand how their terminals work...

Cheers
Sono

 

[scott2000]

If L7 and L8 are 2 halves I don't understand how their terminals work...

They are two different chokes.. L8 may be serving another purpose....... foot switch???....

IDK.... Could use a multimeter with a continuity check to get a feel for what goes where

 

[sonolink]

Ok, I'll try to trace some and report back

 

[mrclunk]

You can also google for faults with the Euphonix/Avid MC control.
Use the same power scheme.  I've repaired one of those before but that was a few dry SMT caps.

 

[sonolink]

Tomorrow my friend is giving me back the MC Control unit so I can compare.
I'll report back.

Cheers
Sono