Avid Artist Mix not powering up

[sonolink]

I've had this unit out of use for a year or so. It used to work fine. I switched it on a few days ago and it blinked briefly shutting down after. Won't power up at all now.

I opened it but couldn't see anything. The external PSU reads proper voltage.
Any ideas about what could be the reason or where to begin checking?

https://drive.google.com/file/d/1c5dh2IuWu_GVDk9nYc9YoH_YvIlkh-qe/view?usp=sharing

Thanks a lot in advance
Cheers Sono

 

[Khron]

"The external PSU reads proper voltage." - is that when disconnected from the unit?

Just the other week, an old friend came in with his Focusrite Scarlett 18i8 that would no longer boot up.
On its own, the wall-wart did indeed put out 12V as it should have, but was no longer able to take the load of the 18i8.

Cracked the case open, and an almighty stank was observed. Sure enough, the two capacitors on the secondary side of the power supply were crapped out. Swapped'em out with Japanese ones, and all was well once more.

 

[pucho812]

yes load vs no load. check the PSU when with a load to determine what is happening.

 

[sonolink]

Mmmm ok. How do I do that? With a 1M resistor for instance? And if so, should I check voltage across what?

I must say that I have another one of these units. They both have the same external PSU and this one (the broken one) won't power up with either PSUs.

Thanks Pucho and Khron

Cheers
Sono

 

[sonolink]

The PSU says OUTPUT 15V/3800mA

Does that mean that I should use a 4ohm resistor?
(15v/3.8A=3.9Ohms)

If so I guess that if I use a 1w resistor that should do right?

 

[synthiaks]

AVID and Switching PSU:s... Sigh.... :-[  we have had some fail i can say!

 

[pucho812]

I would just connect the unit to the PSU and test away.... Ore better yet start with a visual inspection of the PSU

 

[scott2000]

It's scary to say test the working unit with the questionable power supply because it could've been the reason for the non-working unit being goofed now?

Maybe you could take some measurements on the good unit, without power on, and compare to the non-working one....Maybe a diode or something ??

 

[sonolink]

Guys, I'm honestly grateful for all the input but "test away" or "take some measurements" is kinda foggy for me. I'm a live soundman and a guitarist, not an EE, although I try my best to learn and will put all the effort in not just being spoonfed

So I guess we're talking about following the "power path" right? How do I do that onwards from the onboard DC connector? I don't really have a schem...

Cheers
Sono

 

[fazer]

Better find a tech.  If your apprehensive just find a tech.  If in live sound , ask around with your buddies.

 

[PRR]

> I guess that if I use a 1w resistor

My abacus says 57 Watts at full rating.

A part-load test with convenient part could be 22 or 25 Ohms 10 Watts, 0.6 Amps (quite a small fraction of nominal rating but may clarify if the supply or the Mix is the crap-out).

 

[sonolink]

Mmm I see.

The PSU says OUTPUT 15V/3800mA
Does that mean that I should use a 4ohm resistor?
(15v/3.8A=3.9Ohms)

I guess my calculations are wrong then.

Well thanks to all for the help anyway

 

[pucho812]

Guys, I'm honestly grateful for all the input but "test away" or "take some measurements" is kinda foggy for me. I'm a live soundman and a guitarist, not an EE, although I try my best to learn and will put all the effort in not just being spoonfed

So I guess we're talking about following the "power path" right? How do I do that onwards from the onboard DC connector? I don't really have a schem...

Cheers
Sono

Sorry didn't mean to be foggy.  Easy tests to do are isolate the problem. So for example you have the fader pack and an external power supply.  Can you use the mc mix with another power supply? if you can then we know there is a power supply fault.  If you can't  then we know there is a  fault in the mc mix.  Same would be to test the power supply with a known good mc mix.  That is what I would do, the risk of causing another problem or damage would be minimal to nothing. 

 

[sonolink]

Thanks for your help Pucho.
The first thing I tried was to use the PSU on another unit and it works. I tried a different PSU on the faulty unit and same thing happens. It won't power up. My guess is the MC is smoked
I opened it with the hope that something obvious would show up (like some diode or resistor burnt near the DC connector but I can't see anything. I took the photo in case anyone here could see something I couldn't.
I seem to remember a light smell of burnt rubber the very first time I switched it on and it "blinked" for a sec, but my sense of smell is very bad so I'm not positive on that. I can positively remember the part near the DC connector kinda hot (not burning hot but hot like when something has been powered on for some time).

Cheers
Sono

 

[pucho812]

Thanks for your help Pucho.
The first thing I tried was to use the PSU on another unit and it works. I tried a different PSU on the faulty unit and same thing happens. It won't power up. My guess is the MC is smoked
I opened it with the hope that something obvious would show up (like some diode or resistor burnt near the DC connector but I can't see anything. I took the photo in case anyone here could see something I couldn't.
I seem to remember a light smell of burnt rubber the very first time I switched it on and it "blinked" for a sec, but my sense of smell is very bad so I'm not positive on that. I can positively remember the part near the DC connector kinda hot (not burning hot but hot like when something has been powered on for some time).

Cheers
Sono

o.k. so we know that  the fault lies in the MC mix and not the external power supply.  that is good news and bad news. good that we isolated it, bad that we have an issue.  If you are lucky, it might just be a shorted capacitor.

 

[pucho812]

looks like the board has some test points.

perhaps avid can send you some documents on what you should be testing for to further isolate the issue

 

[sonolink]

looks like the board has some test points.

perhaps avid can send you some documents on what you should be testing for to further isolate the issue

Really? Hey that would be great. The MC is registered and everything. I'll email them asking for that. Hopefully they will comply.
I'll report back.

Thanks!!
Cheers
Sono

 

[pucho812]

Really? Hey that would be great. The MC is registered and everything. I'll email them asking for that. Hopefully they will comply.
I'll report back.

Thanks!!
Cheers
Sono

yes tp1, tp2 and so on

 

[sonolink]

Ok so I've been doing some research and apparently it's quite a common problem with these units
And getting a service manual from Euphonix, now Avid, is simply a no-go...

BUT, I've read this very interesting thread:
https://duc.avid.com/showthread.php?t=339096

If the part involved is the cause for the trouble on my unit I should be ok either reflowing it or replacing it. I'll try reflowing it first and report back.

Thanks again for the input and help

Cheers
Sono

 

[sonolink]

I tried reflowing L7 and L8 and nothing has changed BUT 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.

https://drive.google.com/file/d/157YuFNVEF_rMXJccDs3uaAVTFcsOfhK6/view?usp=drivesdk

Any ideas?
Cheers
Sono