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Author Topic: Buck & Boost Transformers  (Read 14267 times)

Mike Sokol

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Re: Buck & Boost Transformers
« Reply #20 on: June 12, 2014, 02:07:00 pm »

RE: PoCo knitting asshole covers...
I'm going to have to remember that one, I like it.

I did a Google search for them, and this is a close as I could find. Would make good presents for some management types I know.
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Mike Sokol
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Stephen Swaffer

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Re: Buck & Boost Transformers
« Reply #21 on: June 12, 2014, 03:11:50 pm »


 but the school plant guys insists it's been like that for a decade. What is it with these plant guys?  >:(


Had plenty of experience in maintenance.  If its been like that and still works, then its not broke so I don't need to fix it.

Breakdown maintenance vs preventative.

To me it is the equivalent of saying "There aren't any idiot lights on. So why should I check the oil in my car?"
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Jonathan Johnson

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Re: Buck & Boost Transformers
« Reply #22 on: June 13, 2014, 02:23:52 pm »

Had plenty of experience in maintenance.  If its been like that and still works, then its not broke so I don't need to fix it.

But in this case, it IS broke. Because of the low voltage, critical systems are not working properly.

The way to fix this is to overload the PoCo's transformer 'til it melts down. Then they have to replace it. 8)

My church (seats 120) recently replaced an old oil-eating, fire-breathing dragon of a furnace with an electric resistance heat furnace (why resistance? Because at 4.75 cents/kWh, and the church occupied <10 hours/week, a heat pump would be dead of old age before the cost would be recouped through savings). That increased our electrical load dramatically, which overwhelmed the wimpy PoCo transformer out on the pole. We had expressed concern about it when we put the furnace in, but they brushed it off, saying if there was a problem they'd deal with it then. To their credit, they dealt with it, putting in a larger replacement transformer at no cost to us.
« Last Edit: June 13, 2014, 02:29:23 pm by Jonathan Johnson »
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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #23 on: June 13, 2014, 02:39:42 pm »

Buck-Boost update: I just got a call from the electrician doing the wiring who reported that with the "Boost" transformer in place they're now getting a solid 121 volts with no load that dropped to 119 volts with several of the HVAC units on. They're predicting another 2 volt drop on Sunday when ALL the HVAC units are running, so maybe this gets down to 117 volts worse case.

If they get through a few Sundays with no buzzing noise, then they can demonstrate to POCO that the low voltage is actually causing a problem and maybe get something changed for free. But in the meantime if this Buck-Boost fix works the pastor will be most happy. Now I'm crossing my fingers that I guessed correctly about the low voltage causing the power supply buzzing noise in the rack. I'll update this thread on Monday once I get feedback from the church but I'm optimistic. 
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John Roberts {JR}

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Re: Buck & Boost Transformers
« Reply #24 on: June 13, 2014, 02:55:04 pm »

Have you tried putting individual gear on VARIAC to see what acceptable low line voltage is for them?

Good luck, sometimes it isn't simple.

JR
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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #25 on: June 13, 2014, 02:56:47 pm »

So here's a good question on the automatic voltage adjuster alluded to earlier in the thread: http://www.sweetwater.com/store/detail/AR1215/

If you have it inline and very slowly adjust the incoming voltage down so that it begins to add "boost" taps, what exactly happens to the output waveform at the instant of switching. Do the have a bunch of zero-crossover Triacs doing the switching, or something as barbarian as relays? If it's relays I wouldn't trust it not to do something bad during the Boost switch point. However, I myself could easily design a Triac circuit to do this electronically with no dropouts, so I've got to assume their own engineers did the same thing.

Have any of you actually looked the output of one of these things with a storage scope while it's switching the voltage? Got a schematic of how they do the switching under load? I want to see this for myself before I recommend the technology to anyone else.
« Last Edit: June 13, 2014, 03:06:15 pm by Mike Sokol »
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Mike Sokol
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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #26 on: June 13, 2014, 03:02:34 pm »

Have you tried putting individual gear on VARIAC to see what acceptable low line voltage is for them?

Good luck, sometimes it isn't simple.

JR

Not yet, and they're a two hour trip each way from me. But if this "shotgun" approach fixes the buzz problem, I'm still going to recommend some future testing. Right now they're ready to shoot the monitor guy every time this happen during a worship service.  But that's probably a bad thing to do in church. :-\  At a rave, maybe... :o

But seriously, a lot of times the apparently complicated problems are really simple once you figure them out. And the intermittent fails are the worst ones of all to troubleshoot. I'm crossing my fingers this is it, but I've been fooled before.
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Mike Sokol
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John Roberts {JR}

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Re: Buck & Boost Transformers
« Reply #27 on: June 13, 2014, 03:13:16 pm »

Not yet, and they're a two hour trip each way from me. But if this "shotgun" approach fixes the buzz problem, I'm still going to recommend some future testing. Right now they're ready to shoot the monitor guy every time this happen during a worship service.  :-\ But that's probably a bad thing to do in church. At a rave, maybe... :o

But seriously, a lot of times the apparently complicated problems are really simple once you figure them out. And the intermittent fails are the worst ones of all to troubleshoot. I'm crossing my fingers this is it, but I've been fooled before.

They are often simple after you determine exactly what is going on...  8)

Yes voltage sag sounds logical, if it sags enough, but larger professional equipment designers accommodate operation around the world where voltage stability is far worse than we generally see here in the US..  Back when euro gear shipped with 220/240V switches some customers used them for some extra help... and would blow up marginal circuitry with over voltage on good days.  :-[  (I recall re-engineering one powered mixer amp module to survive such customer misuse (high line in wrong voltage position.)

Modern universal power supplies generally work down to pretty low line. While it just takes one marginal unit design in the entire path to corrupt the audio. 

JR

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Mike Sokol

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Re: Buck & Boost Transformers
« Reply #28 on: June 13, 2014, 03:39:20 pm »

Yes voltage sag sounds logical...

Modern universal power supplies generally work down to pretty low line. While it just takes one marginal unit design in the entire path to corrupt the audio. 

Yup, and I think that whatever is buzzing right now at 108 volts is probably going to hard fail at some point in the future. But if this wide spectrum cure corrects the problem for now, at least we have a little breathing room and have isolated the problem to a single rack of gear. Then we can experiment with each piece of gear until we find the culprit. Divide and conquer is my motto.  ;D

BTW: I really suspect the old Allen & Heath power supply in the bottom of the rack. Just a gut feel, but that's the first thing I'll put on a big variac to try to force a failure. Of course, if my voltage correction doesn't correct the "buzz" then it's back to square one. We shall see...  8)
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Jonathan Johnson

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Re: Buck & Boost Transformers
« Reply #29 on: June 13, 2014, 04:06:31 pm »

But seriously, a lot of times the apparently complicated problems are really simple once you figure them out. And the intermittent fails are the worst ones of all to troubleshoot. I'm crossing my fingers this is it, but I've been fooled before.

That's my general experience with computer networks. The bigger the problem, the easier the solution. Whole network down? Everyone twiddling their thumbs? It's probably something unplugged. We'll have the network up in 5 minutes.

It's those minor annoyances that can really take up your time and money. Back in the day, I probably spent days trying to figure out why Windows 98 wouldn't shut down properly. Finally I decided that's just the way it is, so that's what I told my customers. (I think I actually DID figure out why it wouldn't shut down. 98 would stop the networking drivers before it finished logging off from the network, so it would hang during log off waiting for the process to complete which it never could do because the network was turned off. Microsoft never issued a fix, so I just told people to hold the power button until it turned off. Thankfully Windows 98 is so far in the rearview mirror I can't see it anymore.)

Must be something about the law of diminishing returns in there.
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Re: Buck & Boost Transformers
« Reply #29 on: June 13, 2014, 04:06:31 pm »


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