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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.


128x128lowrider57

Showing 2 responses by almarg

almarg's avatar
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almarg
9,670 posts
 
@Millercarbon, as someone who has been here for not much more than a year you may not be aware that over the course of many years it has become abundantly clear to long-time participants that Jim (Jea48) knows more about electrician-related matters than pretty much the rest of the membership combined.

I suggest that in the future you think twice before directing insulting and completely unconstructive comments toward highly respected members (and others as well), as you have done on numerous occasions.

Regards,
-- Al

almarg's avatar
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almarg
9,670 posts
 
Hi Lowrider,

DC offset on an AC power line can't be measured with an ordinary multimeter, or with the device you purchased. Although after looking at the description of the device I'm not sure why it indicated an overload. Apparently it automatically senses whether the voltage is AC or DC, and I would have expected it to illuminate the LED corresponding to 120 volts AC.

It might be possible to measure DC offset to some degree of accuracy with an oscilloscope. But a better way would be to construct a low-pass filter that would remove the 60 Hz content, and use that in conjunction with a multimeter. If that might be of interest to you or anyone else reading this thread see the posts by Jea48 and me on page 2 of the following thread (assuming you have the posts sorted oldest first):

https://forum.audiogon.com/discussions/dc-offset-blocker-killer-where-to-buy-in-the-usa?page=2

In any event, good luck in getting the issue resolved.

Best regards,
-- Al
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