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Two stories to tell -

First at an historic vaudeville/movie house of the "atmospheric" motif, so the original electrical service has a very "Dr Frankenstein's lab" vibe, although much of it was decommissioned and replaced with modern service (red herring alert).  In the update the architect specified 208/120 100 amp service for SL and SR (no herring here), below stage level (floor pocket) in power vaults (the orchestra pit and seal room were between them).  Popular band from the 1970s, not my show, call from PA provider about hum/buzz.  "PA is quiet until we connect the monitor split; monitors are quiet until we connect the PA split.  I've used every Pin 1 lift I have, do you have 8?"  PA power is SR, monitor power is SL.

Second is personal, and how I nearly did great bodily harm to another PA provider after I recovered.  "Rock on the Tarmac" at general aviation airport, we're providing additional subs, power, and processing for the subs.  Airport electrician wires in 2 feeders to 2 circuit breakers for 120/240v 100 amp service in a brand new panel in a newly built hanger.  Most of the PA was on one distro, and our sub power and DSP was on a second distro.  Another of those "it's quiet until we put them together" problem.  Audio isolation transformers only changed the sound of the hum; pin 1 lifts were more successful.  I then ask the PA provider if the neutral and ground in each of his distros are unbonded.  "Of course!"  After the show, I do the disconnect at the panel as the electrician is at the other end of the ramp, disconnecting food vendors.  On the second service, the electrician (for reason I'll never understand) stabbed the neutral into the bus bar from the Line bus side.  When I removed it, the neutral feeder wire grazed a line bus 'finger'.  The result was a loud bang and flash (neither of which I remembered immediately after), and a coworker leaning over me asking if I was okay.  Eventually I got up, ears ringing, and followed the feeder to its distro.  I opened the distro, found the neutral and ground bonded (hence the arc flash), so I took my diagonal cutters and installed high impedance air gaps in every conductor, put the cover back on, and vowed to kill that SOB.  Revenge is a dish best served cold and Mother Nature took care of for me a few years later.

So anyone want to guess the problem in the lovey atmospheric theater?

All of this was around 25-30 years ago, and both directly changed the ways I deal with show electrical distribution, how I specify power needs, and how I work as a show electrician.

I get a lot of shit for carefully checking power.  I don't do a gig without using the Extech CT70 it's in my gig box.  I wish that others would invest in them, it even has a tiny 20amp load bank it it!


Anyway Tim, what is a seal room? 

Chasing hum in a situation like that, most of us would have had a similar experience and never thought to check the ground at the panel - it's assumed...   

I'm still in touch with the guy that owned the audio truck on this gig. I sent him this piece, and he sent me back an e-mail with a whole other horror story that I knew noting about. Here's an excerpt:
"...we were powered by a generator that had been Supplied by xxxxxxxx that was rented from a subcontractor who had rented it from a subcontractor. After many hours with no sleep I was pretty happy with everything eventually and then a few hours before showtime things started to sound . . . weird. And weirder. And even more weird. Finally, I went over to the genny but couldn’t find an operator or anybody who knew where the operator was. I climbed in the back and took a look around and the AC I was getting was 94 V at 47 cycles. “Ahh” I said (or maybe it was “aarrgghh”) as I raced back to the truck and threw the breaker. After a while, the operator showed up wreaking of dope, and we got the generator refueled, and things went back to normal, sort of!"
He eventually sold that truck around 1986, and for the next few years I worked for the new owner as lead-technician and truck driver. One of the things I did, about a year in, was install a Sola isolation transformer on the mains inlet.

Two stories to tell -

First at an historic vaudeville/movie house of the "atmospheric" motif, so the original electrical service has a very "Dr Frankenstein's lab" vibe, although much of it was decommissioned and replaced with modern service (red herring alert).  In the update the architect specified 208/120 100 amp service for SL and SR (no herring here), below stage level (floor pocket) in power vaults (the orchestra pit and seal room were between them).  Popular band from the 1970s, not my show, call from PA provider about hum/buzz.  "PA is quiet until we connect the monitor split; monitors are quiet until we connect the PA split.  I've used every Pin 1 lift I have, do you have 8?"  PA power is SR, monitor power is SL.

Second is personal, and how I nearly did great bodily harm to another PA provider after I recovered.  "Rock on the Tarmac" at general aviation airport, we're providing additional subs, power, and processing for the subs.  Airport electrician wires in 2 feeders to 2 circuit breakers for 120/240v 100 amp service in a brand new panel in a newly built hanger.  Most of the PA was on one distro, and our sub power and DSP was on a second distro.  Another of those "it's quiet until we put them together" problem.  Audio isolation transformers only changed the sound of the hum; pin 1 lifts were more successful.  I then ask the PA provider if the neutral and ground in each of his distros are unbonded.  "Of course!"  After the show, I do the disconnect at the panel as the electrician is at the other end of the ramp, disconnecting food vendors.  On the second service, the electrician (for reason I'll never understand) stabbed the neutral into the bus bar from the Line bus side.  When I removed it, the neutral feeder wire grazed a line bus 'finger'.  The result was a loud bang and flash (neither of which I remembered immediately after), and a coworker leaning over me asking if I was okay.  Eventually I got up, ears ringing, and followed the feeder to its distro.  I opened the distro, found the neutral and ground bonded (hence the arc flash), so I took my diagonal cutters and installed high impedance air gaps in every conductor, put the cover back on, and vowed to kill that SOB.  Revenge is a dish best served cold and Mother Nature took care of for me a few years later.

So anyone want to guess the problem in the lovey atmospheric theater?

All of this was around 25-30 years ago, and both directly changed the ways I deal with show electrical distribution, how I specify power needs, and how I work as a show electrician.

I've been fortunate "thus far".  One thing I do differently than in the early days is the use of a proximity voltage tester.  I make sure it's working on a known live circuit and methodically check everything to include face of rack gear.

Ya can't be too careful with electricity or any other aspect of what we do.  Loading trucks, rigging, what-have-you - it can be real dangerous.

I guess the big question I have is do you have to lay out any money of your own or are you just spending some one else's money?

Finally, the USB powering scheme has been rather useful for me: I've powered mine from a USB battery pack, when mains power was unavailable. No issues.


Chris

I just looked at the B website for this and noticed that it's powered by micro USB! That's almost an immediate NO to me. I like the idea as an option but I would want another port on the thing for when the micro port inevitably fails (probably when the mixer gets accidentally yanked off of a table). My reservation is that I wonder if I could "add" another port to it for power. But at $300, it's a bit too expensive to consider it a throw-away but not expensive enough to have a few motorized faders. ??   

Chasing hum in a situation like that, most of us would have had a similar experience and never thought to check the ground at the panel - it's assumed...   

Well, it shouldn't be assumed. If you have anybody (including yourself) tie in a distro, pull out a meter and check every connection. Make sure that everything does what you'd expect, like an actually voltage reading between hot and ground, and a very low voltage between neutral and ground.  And if no discernable voltage between neutral and ground, then make sure there's continuity between the two.

So anyone want to guess the problem in the lovey atmospheric theater?

It sounds like the bond screws (ground to neutral) in the disconnect switches had not been removed.  The neutral shares any current it has with the ground, thereby causing a [variable] drop on the ground reference for the two systems.  You might get away with this today, but 35 years ago the pin 1 problem was much more common, and hum was the result.

GTD

Electronics system issues can manifest in ways we would never imagine.  Year of electronics and avionics.  Common causes of problems are wiring, power supplies and software/firmware corruption.

Recently had an issue with DirecTV Genie DVR in my den system when playing back recorded shows, it would drop out and end the playback at some random time of the playback.  i.e. a 1 hour recording may stop playing at 37 minutes in.  So, I contacted tech support and got a replacement.  Installed the unit, left the old power supply dongle attached as it was zip tied into the entertainment system rack.

Guess what?  Replacement receiver manifested the same issue.  Swapped out the power supply dongle and everything works just fine again.

I can't tell you how many avionics faults and issues we corrected by changing out a power supply or voltage regulator.  Next culprit in aircraft is typically wiring issues.  Those manifest from being disconnected and re-connected, bent around, pulled, unclamped and moved to facilitate access to other things embedded deeper the equipment bay or compartment.  We refer to those as FOM removals (For Other Maintenance).

I put patch panels in all my racks and don't plug and disconnect to equipment for this reason.  Did a 4th of July show for an associate in Hanford, CA at the fairgrounds years ago.  His contract and system.  I went out with a helper with his system and did the show at the fairgrounds while he did an annual festival up north a Mondavi Winery.

Set everything up in the infield on platforms and nothing worked.  Power on, everything hooked up right.  Checked a few more things, then got signal from a source.  After changing out a few cables, disconnecting and reconnecting a few more and wiggling a few it was hitting on all 8 cylinders.  I vowed to never do that with a setup, plug directly into processing gear and amps.

Word.

RJ45 are rated for 1300 insertion cycles.  IIRC, HDMI connectors are not much better.  Both are often directly soldered to PC boards, so any leverage on the external connector is potential for eventual failure inside the device, too.

I've had original Cannon Electric XLR sockets that were easily 30, 40 years old remain 100% reliable but new "other brands" fail in 1/4 that time, some of them side by side in a patch panel.  They don't make 'em like they used to.

I have a Roland UVC-2 "web presentation" AV interface.  USB "blue something".  Using any USB cable other than the one provided with the unit was Quixotian.  Tilting at bytes and bits, but never connecting.

Chasing hum in a situation like that, most of us would have had a similar experience and never thought to check the ground at the panel - it's assumed...   

Two stories to tell -

First at an historic vaudeville/movie house of the "atmospheric" motif, so the original electrical service has a very "Dr Frankenstein's lab" vibe, although much of it was decommissioned and replaced with modern service (red herring alert).  In the update the architect specified 208/120 100 amp service for SL and SR (no herring here), below stage level (floor pocket) in power vaults (the orchestra pit and seal room were between them).  Popular band from the 1970s, not my show, call from PA provider about hum/buzz.  "PA is quiet until we connect the monitor split; monitors are quiet until we connect the PA split.  I've used every Pin 1 lift I have, do you have 8?"  PA power is SR, monitor power is SL.

Second is personal, and how I nearly did great bodily harm to another PA provider after I recovered.  "Rock on the Tarmac" at general aviation airport, we're providing additional subs, power, and processing for the subs.  Airport electrician wires in 2 feeders to 2 circuit breakers for 120/240v 100 amp service in a brand new panel in a newly built hanger.  Most of the PA was on one distro, and our sub power and DSP was on a second distro.  Another of those "it's quiet until we put them together" problem.  Audio isolation transformers only changed the sound of the hum; pin 1 lifts were more successful.  I then ask the PA provider if the neutral and ground in each of his distros are unbonded.  "Of course!"  After the show, I do the disconnect at the panel as the electrician is at the other end of the ramp, disconnecting food vendors.  On the second service, the electrician (for reason I'll never understand) stabbed the neutral into the bus bar from the Line bus side.  When I removed it, the neutral feeder wire grazed a line bus 'finger'.  The result was a loud bang and flash (neither of which I remembered immediately after), and a coworker leaning over me asking if I was okay.  Eventually I got up, ears ringing, and followed the feeder to its distro.  I opened the distro, found the neutral and ground bonded (hence the arc flash), so I took my diagonal cutters and installed high impedance air gaps in every conductor, put the cover back on, and vowed to kill that SOB.  Revenge is a dish best served cold and Mother Nature took care of for me a few years later.

So anyone want to guess the problem in the lovey atmospheric theater?

All of this was around 25-30 years ago, and both directly changed the ways I deal with show electrical distribution, how I specify power needs, and how I work as a show electrician.

AVAILABLE FOR PICKUP IN MONTREAL QUEBEC CANADA.
Email: [email protected]
I will ship at buyers expense. CANADA & USA

For Sale: 2 x NSI Leviton MLC Light & Moving Light Console
DMX 512 XLR 3 + XLR 5 options.

Includes: Little, power cable & pro road case by Caisse Design.

Plus included is one more console that may have issues without case and light.

The two with cases power up and function well. The third powers up and functions but may not be reliable

I have 2 of these kits with cases available & a spare console for parts.

$400 + shipping for the lot including the spare parts board. Or Best Offer This Week!
Must sell Immediately. Email:  [email protected]

AVAILABLE FOR PICKUP IN MONTREAL QUEBEC CANADA.