 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
206.208.226.139
How would I go about testing my line and ground to determine if it is "dirty" or if I just have poor line regulation on the Live wire?
I have a decent digital voltmeter. Connected between Live and Neutral, I get ~127V, with some small oscillation (maybe a 1V variation with a 1Hz time constant). I measure between Live and Earth Ground, I get the same readings. When I switch to DC, I show an average of .1V DC, oscillating between 0V and 0.2V. I'm not sure if the DC reading means anything, as it may be an artifact of the meter.
I don't measure any appreciable voltage (either AC or DC) between Neutral and Ground.
Are there any other tests I can perform with a DMM and maybe some simple circuits?
Follow Ups:
testing the earth gounding connection is not at all easy.
first you require another gound reference (a Vgood ground connection) say a 10ft copper rod or pipe into the ground (Tesla used to bury large copper plates 50+ft down to ensure a reasonable earth connection.
then you require a low impadance measuring bridge with the correct filters etc. This is a real EE job, and best left to the pro's.
Your DVM cound be giving allsorts of mis-readings and other noise pickups.
given that everthing will be relative to the earth connection and all differential voltages will be relative to whatever the earth is then i dont think you should overly worry at this point in time. There are greater caused of problems elsewhere.
sorry i konw it not a lot of help but i thought i would mention it before you go off on a wild goose chase.
As a side note it was only recently that i discovered when my 3 phase mains was being redone at the intake due to a live1 to live2 to earth short putting my mains voltage to 315v, that my apartment doesnt actually have any earth per-say. The "earth" is actually connected to the neutral wire at the intake!
Do you have some reason to believe that you have a power line noise problem? From what you describe it doesn't seem overtly defective. Dirtiness is in the ear of the beholder and the brain of the equipment designer. It takes a combination of equipment susceptibility and a source of noise to which the equipment is susceptible to have problems.
So, keeping the above in mind, I use a little portable AM transistor radio. The most common sources of noise will have emissions that you can hear easily between stations and trace down using the directional loopstick antenna. The rub is that while it might help you find something that's causing problems, you may flip out worrying about all the noise sources that you find that aren't. Focus on noises on the circuit(s) that run your equipment and try to find where they are coming from.
One thing you will notice is that you will hear every switch-mode wallwart when you get within a few feet of it. But if they drop off rapidly with distance and you don't hear the same noise on the circuit that's running your gear you're probably OK.
One thing I like about using the radio is that you can often identify various sources by their sounds. For instance, if I hear a certain sort of noise on a circuit that I care about, I can wander around the house listening for something that produces that sound. And when you're not messing with your stereo, you can us it to listen to the game...
Rick
To really get a handle on your AC quality, U need an O-scope or U could borrow a noise sniffer from The Cable Co. which will audibly tell U how much garbage is on your line.
Without AC regeneration, or a line stabilizer, U are at the mercy of your local power Co. for AC stability but when it comes to noise, there are a myriad of products that deal with line/GND noise.
Some research/recommendations would be in order here.
Cheers,
~kenster
Hi.
I tested it with a wideband powerline & EMI noise analyser which reads out the the levels of the dirty stuff riding the AC mains.
From its built-in loudspeaker, I also hear radio broadcasts coming out from the wall outlets in a few different domestic locations powered via different hydro companies !!!
Go figure how dirty are our powerlines!
c-J
I believe I might have a Low Freq oscillation (1 to 5Hz) of at most 2V riding on my Line.
Would a high-pass filter (series cap with shunt resistor or shunt choke) work to eliminate it? Would I put such a network before or after the mains transformer? Or is that just crazy thinking?
Hi.
Frankly it's news to me when you replied my post in the Tube/DIY forum
that LF oscillations (i.e. "motor-boating") still occur even when all the tubes (including the retifier tube) of your amp are pulled out !!!
How can this happen? Where comes the LF energy to move the speaker cone?
Any powerline craps must go through the amp first before going to the loudspeaker. But you said there is no amp as the power amp is not working (with all tube pulled out)?
It doesn't make sense to me. Bud.
I'd address to the powerline filter issue later once the mysterious motor boating on the speaker cone is resolved.
c-J
I meant just the preamp signal tubes are pulled. The rectifier is of course still in, as are all the tubes in the amp itself.
Check the schematic in that same thread. There are "safety" resistors which tie the B+ to the output just in front of the output coupling capacitor. When the output tubes are pulled, the PSU noise is directly coupled to that output cap, and the LF oscillation looks like LF signal.
And, I am measuring the AC at the wall with a couple multimeters, both a digital and analog DMM. I can watch the needle wiggle, and the digital meter seems to track up and down in a periodic manner with about a 1 second period.
Though your voltage is high the readings seem to be as they should be. There should be no voltage between neutral and ground. The DC reading on an AC line is not uncommon and is sufficiently low to not cause any problems.
So, I guess i just have a dirty Live line, then.
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
