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[TJ (Tom) Cornish]

The CT70 saves having to carry around a heater in the summertime, and the little noncontact tester can help identify a RPBG that the multimeter and CT70 would both miss, so the CT70 OR multimeter plus a noncontact tester would be a complete set except for missing major deviations from sine waveform. I liked the 3 light tester plus noncontact tester as a quick screen, but you make a good argument that without a parallel load, those won't find excessive voltage sag under load. What do people think is the value added of looking at the waveform under load? Worth doing?

Looking at a waveform under load may be interesting and you may learn something - like how poor power factor distorts the waveform, but then what?  What does a waveform with 5% distortion look like?  How about 25%?  Without a real measurement module, not just guesstimates from the 8-bit scope picture like how most low-end scopes work, you won't know. Even if you do know how dirty the power is, how do you fix it?  Turn off the house lights? Turn off the VFDs driving the air handlers?  Turn off your own amp rack which is probably causing some amount of junk on the power system for everybody else?

The only scenario where an oscilloscope would actually make a difference is if you were in an auditorium with a big dimmer system and you were trying to figure out if a receptacle was fed from the dimmer rack or not. In every other case I can think of, a multimeter with load gives more useful data - voltage drop, neutral to ground voltage, whether the receptacle is wired correctly, etc.  With this data you can decide to try to find another circuit, which is pretty much your only recourse anyway (though your power distortion will almost certainly follow you unless you can find separately derived power, which may exist, but is probably very far away from you).

Your next task is to buy or build a "poor man's distro" which bonds the ground wires of multiple circuits together while not connecting the hots or neutrals. This will solve lots of noise and safety issues, as our gear is almost always more sensitive to junk on the ground wire than on hot or neutral. 

[Kevin Conlon]

The crux of the issue is in boldface.

I suggest Kevin C. taking a look at Guy Holt's profile and clicking on "show posts".  Guy has spent a fair bit of time posting about "dirty" power - what it really is, how it gets that way and what (little) can be done about it if the offending device(s) cannot be powered from a separate source.

The take away I got from Guy's posts is that many of the problems attributed to dirty power are failures or shortcomings in product designs or failures of grounding and bonding practices.

I've never had "dirty power" from a "real generator".  I've had unbonded neutrals, found loose internal connections, poor frequency control, etc.. but genuinely dirty power from an M-Q Whisper-Watt or similar generator?  No.

Thanks, i will check that out. A lot more to it than i thought. The ct70 will get looked at also. I have a good fluke meter and ncvt and use them on all power connections i make. I was wanting to know how much more i could do and all of you have been very helpfull, thank you. Years ago when honda generators were belt driven i knew more about gen. power as i had to fix them. Forty years of new learning has pushed it into some far corner of my brain. I did build a load board out of 500 watt bulbs some 100 watt and a 50 so i could load and test them after a repair. Thanks again to all.

[Mike Sokol]

The CT70 saves having to carry around a heater in the summertime, and the little noncontact tester can help identify a RPBG that the multimeter and CT70 would both miss, so the CT70 OR multimeter plus a noncontact tester would be a complete set except for missing major deviations from sine waveform. I liked the 3 light tester plus noncontact tester as a quick screen, but you make a good argument that without a parallel load, those won't find excessive voltage sag under load. What do people think is the value added of looking at the waveform under load? Worth doing?

For my own gigs I first use a Fluke 117 for a voltage test on the genny for voltage and phase (many large generators can be set for various outputs such as 120/240 or 120/208 and 277/480, etc...). Plus I use it for basic ohm readings on ground bonds. I also use an Ideal Suretest analyzer on any house power as well as my stage stringers to make sure there's been no breaks in the EGC (Equipment Grounding Conductor), plus a quick check with a VoltAlert for RPBG (Reverse Polarity Bootleg Ground). I give my stage crew a 3-light tester and a Fluke VoltAlert and have them do a quick check on every piece of stage gear that's plugged in during a show. At least a few times a year we get a guitar amp with a hot chassis which we swap out, and I see at least several lost-grounds in wall outlets, especially hotel banquet rooms. On the average I run into one RPBG a year in churches with "upgraded" outlets. Ugh....

This power test procedure only takes me around 5 to 10 minutes before I declare the power is safe to the rest of the crew. And they know to NEVER plug in or power up until I give the all clear. Of course when I measure anything suspicious at all I go into diagnose mode and develop a workaround (secondary bonding connection, run an extension cord to another outlet, etc...). I'll put a piece of tape on any house outlets that don't pass the test and tell hotel management it needs to be corrected. I suspect they just rip the tape off after I leave, but at least I tried...

[David Buckley]

Looking at a waveform under load may be interesting and you may learn something - like how poor power factor distorts the waveform, but then what?  What does a waveform with 5% distortion look like?  How about 25%?

Exactly.

The easiest approach is to have a power quality meter on the distro; most folks have multiple meters on there anyway, and the power quality meter measures everything the voltmeter and ammeters measure, plus provide quality info, and many of them are logging and/or have bus outputs these days so one can record the data over a period of time.  And they no longer cost tens of thousands of dollars either, even available from Ali.

[Scott Helmke]

It seems we may have had a similar discussion before... what nature of power problem are you looking for?  A cheap wallwart power supply, with AC output could step down and isolate the mains power to something you could listen to... This may not reveal very HF interference, but problems in the audio range could be picked up.

In fact we had a discussion that ran to several pages!
http://forums.prosoundweb.com/index.php/topic,158738.0.html

[Phil Graham]

From my experience, power quality analysis is beyond the reach of most casual users... I just got test results back yesterday from a test we had done-what "I can do about it" is add line reactors on VFDs and a capacitor bank on the incoming power-beyond anything most are going to do at a gig.

1000X this. Getting SMPS based luminaires to successfully function in industrial environments is part of my day job. Logging power meters can give you high quality 3ph V-I graphs, but ultimately the underlying transients are fairly mundane things like VFD hash, contactor arcing, and inductive kickback.

The external solutions amount to line reactors and snubbers. And then at the power company scale you can use something like a synchronous condenser.

The internal solutions are varied, but amount to either absorbing or shunting transients.

[Scott Helmke]

True, you can't easily clean up dirty power.

But at least you can go outlet shopping, which might find a cleaner source.  I've done a lot of shows in a venue where two of the three legs tend to be noisy, but the third is usable for susceptible gear.

[TJ (Tom) Cornish]

... but the third is usable for susceptible gear.

Maybe, or maybe you can't find a spot.

All of my gear 10 years old or newer is fine.  I have one room where my Mackie SRM-450 gen 1 speakers buzzed even when the only cable plugged in was the power cable - even with a cheater plug.  The best solution for me was replacing them with something more modern and better shielded against the pin-1 problem and just shielded better in general.  YMMV and I understand that gear still producing ROI is hard to get rid of, but for me this was the best way forward.

[Ike Zimbel]

Maybe, or maybe you can't find a spot.

All of my gear 10 years old or newer is fine.  I have one room where my Mackie SRM-450 gen 1 speakers buzzed even when the only cable plugged in was the power cable - even with a cheater plug.  The best solution for me was replacing them with something more modern and better shielded against the pin-1 problem and just shielded better in general.  YMMV and I understand that gear still producing ROI is hard to get rid of, but for me this was the best way forward.

I could be wrong, but it is my understanding that Mackie products have had the Pin-1 problem sorted from day-1 (this from the late Neil Muncy, who identified the Pin-1 problem). That said, if screws and nuts get loose, the Pin-1 problem can rear it's head, even with gear that has it sorted...you need a solid, clean, connection to chassis for the Pin-1 solution to work. This is why even PCB mounted XLR's, (for example) will still have at least one mounting screw. The screw is the chassis ground connection.

[Mike Sokol]

I could be wrong, but it is my understanding that Mackie products have had the Pin-1 problem sorted from day-1 (this from the late Neil Muncy, who identified the Pin-1 problem).

Not true. I use Mackie SRM350 speakers in my No~Shock~Zone ground loop hum demonstration, and they're one of the worst offenders of pin-1 problem.

[ProSoundWeb Community]