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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
lowrider57's avatar
lowrider57 OP
5,411 posts
 
Thanks @lak  for that valuable information.

@almarg , I've been reading that thread.
The Klein device does register 120VAC, but the Overload LED is lit. The polarity LED's indicate normal AC, maybe the overload is due to high DC. Overload is >25vDC.
And I know not to use a multimeter, that's why I bought this device. Thanks.

@jea48 , I think I should call the electrician to address the breaker situation. The 20A breaker being tripped at every powerup has never happened before this week.
Would he be able to measure DC offset?


lowrider57's avatar
lowrider57 OP
5,411 posts
 
I should mention that this unit is one year old and was purchased used. It was manufactured by Core Power Technologies.

I'm thinking that I should start with a call to my electrician before sending the unit for service. 
I wonder if a DC blocker can be installed in this conditioner as it is in my amp.
Thanks everybody.


testpilot
909 posts
 
Equi=Core and Core Power Technologies are the same company.
lowrider57's avatar
lowrider57 OP
5,411 posts
 
@testpilot , true, but not anymore. Core Power Technologies is out of business and has been purchased by Underwood. All new sales and R&D are done at a new facility.

jea48
4,393 posts
 
lowrider57 OP


I think I should call the electrician to address the breaker situation. The 20A breaker being tripped at every powerup has never happened before this week.
Would he be able to measure DC offset?

Good chance the electrician will look at you scratching his head. DC on the AC mains?

I have never head of DC on the mains causing a 20 amp branch circuit breaker to trip open.

If it where me I would pop the top cover off the unit and have look inside. Use your nose and sniff around inside. Look and smell for something that looks and smells burnt. Especially look around the top support mounting plate for the toroid transformer as well at the bottom of the transformer if it rests against the metal bottom of the unit.

Also check where the AC hot wire leaves the power switch to see if there is a DC blocker circuit/device/components between the switch and the primary winding of the toroid transformer. Hard to believe it doesn't have one. I would imagine the transformer is a 2Kva (2000 Va) rated transformer.


When you hire an electrician to change out the 20 amp breaker in the sub panel, you might ask him to have a look inside the Equi=Core unit.

Jim
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