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Equi=Core Hum & Other Issues

I’ve owned a Core Power Tech Equi=Core 1800 for 6 months. Recently the transformer has started to hum inside the chassis. It happens when components are on and also when sources are powered down. The transformer hum is intermittent. It ranges from multiple times per day to 3 or 4 days without any hum. I never had DC on my dedicated lines before, so I picked up a Klein Tools AC/DC tester... https://www.kleintools.com/catalog/electrical-testers/electronic-acdc-voltage-tester-12-240v-ac-15-2...
and when plugged into wall receptacles it indicated overload. Line voltage is steady at 122VAC and always has been.
What am I doing wrong, and how should I test for DC on the power line?

I discovered another problem when testing the Equi=Core duplex receptacles; they indicate inverted polarity. All house outlets measure correct polarity.
I’m looking for some assistance in diagnosing this hum. I’m not sure if it’s due to DC offset or if the torroid itself is vibrating in its mounting.

I know this is becoming a long thread, but I must mention that the Equi=Core now trips the breaker at the panel when powered on. It trips several times in a row, eventually allowing power-up. This is a 20A dedicated line from a subpanel which I’ve had for years.
Any advice is much appreciated.


lowrider57
lowrider57's avatar
lowrider57 OP
5,418 posts
 
@erik_squires 
After finding the corroded line in the meter,  moving the system (2- 20A lines) to the opposite leg greatly reduced the volume of the hum in the Equi=Core. When this hum presented and for the past month, it was so LOUD that it could be heard in the next room. Now it is many dB lower, but still audible from 12 ft. away.
As far as to how frequent it hums, it's too soon to say.


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lowrider57's avatar
lowrider57 OP
5,418 posts
 
So, the corrosion in my meter box is causing distortion in the mains. Moving my subpanel to the opposite leg stopped the Equi=Core hum for awhile, but now it's back.

 Does anybody know if a toroidal transformer can be damaged due to longterm hum from harmonic distortion?

 @jea48 , I saw your comments regarding this subject on the other forum. My concern is that this harmonic distortion may cause damage to the Equi=Core and my Atma-sphere amp which is also experiencing hum.



cleeds
6,246 posts
 
lowrider57
... the corrosion in my meter box is causing distortion in the mains.
That's potentially hazardous. Your electric utility should install a new meter and/or meter pan, as needed.
 Does anybody know if a toroidal transformer can be damaged due to longterm hum from harmonic distortion?
That seems unlikely.
lowrider57's avatar
lowrider57 OP
5,418 posts
 
Seems unlikely?
Thank you @cleeds .
That's potentially hazardous. Your electric utility should install a new meter and/or meter pan, as needed.
I know. Unfortunately, the homeowner is responsible for the maintenance of the meter pan and meter drop onto the property.
There's a water leak in the conduit from my roof down to the meter and the seal into the pan has worn away. The estimate from an electrical contractor is $2000 and money is tight right now. I need to get some more estimates.


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