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Author Topic: SC48 shuts down before show.  (Read 11435 times)

Nitin Sidhu

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SC48 shuts down before show.
« on: September 26, 2011, 04:33:18 am »

Hello!

The past weekend I was engineering, and in charge of Sound and lights reinforcement, for what would arguabally be the most important production for me this season. The FOH console shuts down with a thud at the nth moment.

I have a thread on at the DUC for those interested.
http://duc.avid.com/showthread.php?t=308126

I would really appreciate a better understanding of what could've happened.

Regards,
Sidhu

Quote
Main event for the Indo-German festival. Inaugaration. Approx 5K in attendance. German and Indian percussion ensemble. Maxing out the SC48. Using sub mixers for WL, Video and Electronic stems. JBL Vertec 4886/4888 deployment. Running 3 time aligned zones.

Gates at 7pm. Stage blackout at 6:45pm. Im just begining to SC the main act, Sivamani.

5:30pm loud pop from PA. I am on stage with my ipad controlling the Venue via VNC. VNC disconnects.

Console is in power off mode. Connected to a UPS on primary power supple, and direct to distro on secondry power supply. Also connected to the UPS is my laptop, router, Soundcard and phone charger.

On trying to repower the console, all i get is a clickty click sound of the relay I think, a few seconds pause and then same thing.

I have an M7 as a backup, but i realize no way im gonna get everything redone again. Already on call with Avid support in Bangalore.

A few calls to and fro, and im told this situation arose recently with another console, and the output card is fried. And short of replacing it, nothing can be done. So I give that a thought, lack of another card, and the possibility of a replacement SC48 within the hour, and Im willing to swap the Hard Disks as long as I can have my most recent setting back. Never mind me not having checked the main act. They say it could be possible. (I could also swap the card, in retrospect)

More brainstorming with bangalore and the thought of maybe trying to boot the console without the output card connected arises. So we start to unscrew the the top.

The Germans see the console being ripped apart and now they flip. Im seriosuly grateful to them for having held off so far.

We disconnect the ribbon, and Voila! the console boots. I recover what I can. Wait for the replacement board to come in. 5 minutes to curtain. I am repatched and a little nervous.

Show starts with a speech by the German ambassador to India and other dignitaries. The entertainment begins with a loud squeal, but then on we had a great gig!

Christoph Haberer from germany is a wicked drummer!

I would need some serious consuling to get my faith back.
At least need to know what could've gone wrong ? Everything else connected to that power supply and phase in general is still working great. The power distro was tested, and retested to be a stable 235v @ 51cycles, with the load on. All grounding was intact.

The console was not in the sun or in humid conditions, it was pleasent weather.

Regards,
Sidhu
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Sheldon Radford

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Re: SC48 shuts down before show.
« Reply #1 on: September 26, 2011, 12:29:45 pm »

Hi Sidhu,

As mentioned on the DUC post we'll be looking into this to figure out what might have caused the issue. Given that removing the card resolved the problem it could have been that the damaged card was somehow shorting/affecting the power supply, but that's just a guess.

Sorry again for the added stress.

Sheldon Radford
Avid
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Nitin Sidhu

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Re: SC48 shuts down before show.
« Reply #2 on: September 27, 2011, 02:24:33 am »

Thanks Sheldon!

Response from Avid has not been short of reassuring.

Regards,
Sidhu



Hi Sidhu,

As mentioned on the DUC post we'll be looking into this to figure out what might have caused the issue. Given that removing the card resolved the problem it could have been that the damaged card was somehow shorting/affecting the power supply, but that's just a guess.

Sorry again for the added stress.

Sheldon Radford
Avid
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Kevin Maxwell

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Re: SC48 shuts down before show.
« Reply #3 on: September 27, 2011, 01:33:06 pm »

Thanks Sheldon!

Response from Avid has not been short of reassuring.

Regards,
Sidhu
You mentioned on the Avid user forum
ďA study of the output card showed a short on channel 12. Channel 12 was feeding the video guys. I am not too sure if they had isolation in place.Ē

When doing a show with a sound system we brought in I had a couple of outputs die on a DSP that was feeding the in house system, we were just using the delay speakers. The unit continued to work I just lost those outputs. We used another DSP just for those feeds to get thru the show. Now whenever I work that room I use line level isolation transformers between the DSP and their system. The sound company owner thinks I am being paranoid but he lets me do it.

It is disturbing to think that a problem with an output is enough to take down the whole console. I will go as far as to say that it sounds like a design flaw that needs to be fixed.

I had a cheap measurement mic die on me when it got plugged into a true 48volt phantom power instead of its own preamp that was much lower in voltage. The manufacturer fixed it (and updated it so it wouldnít happen again) for free even though it was many years out of warranty.
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TJ (Tom) Cornish

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Re: SC48 shuts down before show.
« Reply #4 on: September 28, 2011, 09:11:30 am »


It is disturbing to think that a problem with an output is enough to take down the whole console. I will go as far as to say that it sounds like a design flaw that needs to be fixed.
+1  If it is true that something as simple as a shorted cable can crash the board, that's a serious FAIL.  I don't care how good it sounds if it won't power up...
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Sheldon Radford

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Re: SC48 shuts down before show.
« Reply #5 on: September 28, 2011, 01:42:25 pm »

+1  If it is true that something as simple as a shorted cable can crash the board, that's a serious FAIL.  I don't care how good it sounds if it won't power up...

Shorting an output or connecting to an input with +48V will not damage the outputs. They are protected against these types of incidents.

What's known at this time is that the output was subjected to a very high voltage/current from the connected equipment - far beyond what standard protection mechanisms can handle and of sufficient strength to burn the traces on the PCB and damage many of the components in line. This is exceptional.

Fortunately the support team was able to sort out a replacement console for the first day, and by my understanding the original console was used the next day (with a replacement output card), showing there was no permanent damage to the console or PSU.

Sheldon Radford
Avid
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Kevin Maxwell

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Re: SC48 shuts down before show.
« Reply #6 on: September 28, 2011, 03:37:32 pm »

Shorting an output or connecting to an input with +48V will not damage the outputs. They are protected against these types of incidents.

What's known at this time is that the output was subjected to a very high voltage/current from the connected equipment - far beyond what standard protection mechanisms can handle and of sufficient strength to burn the traces on the PCB and damage many of the components in line. This is exceptional.

Fortunately the support team was able to sort out a replacement console for the first day, and by my understanding the original console was used the next day (with a replacement output card), showing there was no permanent damage to the console or PSU.

Sheldon Radford
Avid

Its good to know that the outputs are protected against the normal things. But of course the abnormal is always what really gets you. Thatís why as I said when connecting to the outside world (things that arenít completely under my control) I like to use isolation transformers. Are these output cards offered with transformer-isolated outputs? It probably would be too expensive and just cheaper to isolate the outputs that could be a potential problem. I never trust video world, maybe because most of my work used to be doing sound for video and some film.     

So I assume that in a startup self test the console sensed a problem with the output card. Or it couldnít even get past the problem as it tried to startup. It would be nice if it would notify you of the problem and continue to work minus the blown outputs. But I have seen some very minor things prevent a computer from starting up. And needless to say thatís what the consoles basically are.

Are there any parts that might be good to carry as spares to be on the safe side? Besides another console.
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Nitin Sidhu

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Re: SC48 shuts down before show.
« Reply #7 on: September 29, 2011, 02:12:28 pm »

Hello!


I only seek guidance to avoid such issues.

Let me get a few things clear.

>The board has NOT been out for a gig ever since. A replacement output card was available the next day, and installed.
>We only checked all inputs on the board and found them to be  working yesterday.
>I did not realize the replacement board came in from an official channel. We requested a fellow vendor in town to send his in if possible. None the less, I am highly obliged, and have shared my thanks.
>Support from Avid has been prompt.
>I am a sound engineer and not a vendor. My preferred vendor bought the board on my request.

Now, there have been similar cases. I can almost guarantee that with the instant answers I got for my problem.

My console was not powering up successfully. There was no deliberation over what could be the problem, I was told in AN INSTANT : "The output card is fried. A similar case was faced recently. Nothing can be done.". Period.

I again appreciate the truth. But does this only happen with the SC48's or is this a mere coincidence ? Never ever heard of another console ever going down.

Therein lies my problem.

Regards,
Sidhu




Its good to know that the outputs are protected against the normal things. But of course the abnormal is always what really gets you. Thatís why as I said when connecting to the outside world (things that arenít completely under my control) I like to use isolation transformers. Are these output cards offered with transformer-isolated outputs? It probably would be too expensive and just cheaper to isolate the outputs that could be a potential problem. I never trust video world, maybe because most of my work used to be doing sound for video and some film.     

So I assume that in a startup self test the console sensed a problem with the output card. Or it couldnít even get past the problem as it tried to startup. It would be nice if it would notify you of the problem and continue to work minus the blown outputs. But I have seen some very minor things prevent a computer from starting up. And needless to say thatís what the consoles basically are.

Are there any parts that might be good to carry as spares to be on the safe side? Besides another console.
« Last Edit: September 30, 2011, 12:18:03 am by Nitin Sidhu »
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Brian Ehlers

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Re: SC48 shuts down before show.
« Reply #8 on: September 29, 2011, 06:37:58 pm »

Its good to know that the outputs are protected against the normal things. But of course the abnormal is always what really gets you. Thatís why as I said when connecting to the outside world (things that arenít completely under my control) I like to use isolation transformers.
While transformers may offer some overvoltage protection, there are plenty of events which will march right on through the transformer and still potentially damage circuitry.  For example, if one leg of the isolated differential pair gets shorted to 115V mains, that 115V 60 HZ AC signal will go right through the transformer as if it were an audio signal.  If the protection components (varistors, transorbs, etc.) try to clamp that voltage but aren't sized to handle that much power (especially for a continuous short), they'll blow and possible take out other circuits with them.

Good audio transformers will even pass common-mode transients -- even though common-mode is exactly what a transformer is supposed to reject.  The very characteristics which make a transformer good for audio also creates capacitance between the primary and secondary windings.  A lightning strike nearby may create a high-voltage transient on both legs of the isolated differential pair;  some of that transient will travel through the winding capacitance and hit your outputs.  Is it enough to blow the protection devices?  Maybe.
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John Livings

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Re: SC48 shuts down before show.
« Reply #9 on: September 29, 2011, 07:28:29 pm »

 [I never trust video world, maybe because most of my work used to be doing sound for video and some film.]

Hi Kevin,

Not to Hi-Jack the thread, Would it be possible to post a simple diagram of the DI box inserted into your chain? (Showing the entire chain)

Also as you mentioned video, what did you find most successful for recording cameras to a recorder?

I know the questions are basic, As we do small Theater Productions and just started adding some Live Instruments.

Always looking for ways to improve audio.

Now we use 16 mics, 10 wireless and 6 wired. We use the 16 D.O. of the mixer to go to an Alesis HD 24 XL, and was wondering the best way to get one channel of each of the 4 cameras into the HD-24.?

The Cameras have XLR out, and I just record to tape and at least I have back-up.

Any thoughts would be welcome, I will be more than happy to start a new thread if that would be better.

Regards,  John

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Re: SC48 shuts down before show.
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