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Author Topic: SC48 Phantom Power Issue  (Read 2159 times)

Dave Barker

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SC48 Phantom Power Issue
« on: January 19, 2017, 02:16:28 pm »

On inputs 11 & 12 (top layer) when I engage phantom power on the channels I get a "pulsing" input signal indication. If I remove phantom it goes away and it does not appear on any other channels and does not appear on the same faders on a lower layer.

With phantom on the channel it works fine I have input no problem. The channel also works fine with out phantom. I don't hear any noises or pulsing when cued up.

Just have this pulsing input signal.

Any ideas? Anybody seen this before.

I did put this on the Avid site just thought I would put it here also. 

Thanks
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Tim McCulloch

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Re: SC48 Phantom Power Issue
« Reply #1 on: January 19, 2017, 02:32:31 pm »

On inputs 11 & 12 (top layer) when I engage phantom power on the channels I get a "pulsing" input signal indication. If I remove phantom it goes away and it does not appear on any other channels and does not appear on the same faders on a lower layer.

With phantom on the channel it works fine I have input no problem. The channel also works fine with out phantom. I don't hear any noises or pulsing when cued up.

Just have this pulsing input signal.

Any ideas? Anybody seen this before.

I did put this on the Avid site just thought I would put it here also. 

Thanks

So you're seeing a cyclical "surge" on the input channel's meter but not hearing anything over headphones?

Does this continue if you disconnect the physical inputs to console for those channels?
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Dave Barker

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Re: SC48 Phantom Power Issue
« Reply #2 on: January 19, 2017, 04:18:35 pm »

Correct I am seeing a pulsing of the meter from -45 to -30 on the screen and on the LED's on the channel strip as well.  Very small.  If I go to the patchbay de-select the input 11 from fader 11 so there is no input going to it, it goes away.  If I patch input number 5 to fader 11 and apply phantom it does not do it.

When I cue up the channel it is clear no noise at all.  No pulsing or anything like.  I plug in a microphone that requires phantom works fine no "noise". 

And this is happening with absolutely nothing plugged into the console.  I have also tried loading one of the preset shows and it still does it not just a show that I have created.

We are on current firmware.  I don't know how long this may have been an issue before, not sure if I had to apply phantom to that channel in previous shows, that is only way I would have ever seen it.  Just happen I was programming a show for this weekend and needed phantom on ch 11.

Just have this pulsing green meter on the page.

Thanks
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Eric Vogel

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Re: SC48 Phantom Power Issue
« Reply #3 on: January 19, 2017, 05:42:16 pm »

On inputs 11 & 12 (top layer) when I engage phantom power on the channels I get a "pulsing" input signal indication. If I remove phantom it goes away and it does not appear on any other channels and does not appear on the same faders on a lower layer.

With phantom on the channel it works fine I have input no problem. The channel also works fine with out phantom. I don't hear any noises or pulsing when cued up.

Just have this pulsing input signal.

Any ideas? Anybody seen this before.

I did put this on the Avid site just thought I would put it here also. 

Thanks

I have repaired several headamps in SC48/MixRack/StageRack... Here's a few things you can do to isolate the issue:

1.  use a 'Y' cable (F-2xM) - plug into CH10 (phantom on) & CH11 (phantom off), do not plug a mic load - leave open circuit - look at meter on CH11 and listen.... note results

2.  CH11 - make a plug (M xlr with pin2 jumped to pin1, pin3 jumped to pin1) turn off phantom before inserting this plug!!!! after plugging in the plug, turn on phantom.  This puts a full 14ma load on phantom circuit and also shorts the differential inputs so all you are listening to is the self noise of the preamp.  Look at meter and listen... note results.

3.  If after #2 you have a DMM with DC current measurement, replace the jumps in the plug above with DMM meter leads to verify the phantom circuit is sourcing 7ma per leg full load.

With Venue in particular, do not hot plug loads (mics/Di's) with phantom on - This will lead to eventual failure of at least one component.

-Eric
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David Sturzenbecher

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SC48 Phantom Power Issue
« Reply #4 on: November 03, 2018, 10:21:40 pm »

Correct I am seeing a pulsing of the meter from -45 to -30 on the screen and on the LED's on the channel strip as well.  Very small.  If I go to the patchbay de-select the input 11 from fader 11 so there is no input going to it, it goes away.  If I patch input number 5 to fader 11 and apply phantom it does not do it.

When I cue up the channel it is clear no noise at all.  No pulsing or anything like.  I plug in a microphone that requires phantom works fine no "noise". 

And this is happening with absolutely nothing plugged into the console.  I have also tried loading one of the preset shows and it still does it not just a show that I have created.

We are on current firmware.  I don't know how long this may have been an issue before, not sure if I had to apply phantom to that channel in previous shows, that is only way I would have ever seen it.  Just happen I was programming a show for this weekend and needed phantom on ch 11.

Just have this pulsing green meter on the page.

Thanks

Hey Dave,
Did you ever get to the bottom of your issue? On a gig now with an SC-48 with this exact issue happening on CH10.
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Scott Helmke

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Re: SC48 Phantom Power Issue
« Reply #5 on: November 04, 2018, 03:39:33 pm »

We've got one too, had it happen with a Profile Stage Rack. Basically it's a bad (possibly damaged) input.  Costs $300-ish? to send the whole card into Avid for repair, would be nice if there was a cheaper in-house fix possible.
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Tim McCulloch

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Re: SC48 Phantom Power Issue
« Reply #6 on: November 04, 2018, 09:21:59 pm »

We had this issue on a different channel, Avid swapped out the input module for the price of shipping as we were only a few months out of warranty.  Not sure what it would cost now that the desk is 6 years old.

Later we had similar symptoms but before I pulled the input card I had to do other work inside (re-seating the HUB48 and mix engine cards in the PCI bus extender cage, and the TDM jumper but that's another story).  After putting the desk back together I didn't immediately notice but the channel ghost had been exorcised.  It might be worth the hour it takes to re-seat all connections between the input module and HUB48 card, and re-seat the HUB48 in the extender cage.
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"Practicing an art, no matter how well or badly, is a way to make your soul grow, for heaven's sake. Sing in the shower. Dance to the radio. Tell stories. Write a poem to a friend, even a lousy poem. Do it as well as you possible can. You will get an enormous reward. You will have created something."  - Kurt Vonnegut

Jean-Pierre Coetzee

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Re: SC48 Phantom Power Issue
« Reply #7 on: November 05, 2018, 07:20:53 am »

... It might be worth the hour it takes to re-seat all connections between the input module and HUB48 card, and re-seat the HUB48 in the extender cage.

This is worth a check, it's the general solution for SC48 issues. Have had numerous problems with our console sorted out this one, even recently had the console randomly shutting off, thought it was a faulty supply but was just a connector that needed to be reseated.
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Word & Life Church

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If you want "watts"-then plug in a toaster"
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