@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.
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.
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.
Showing 49 responses by lowrider57
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? |
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. |
Thanks @jea48 . I always appreciate your help. I've read about mods where the torroid is removed from the bottom of the chassis and a layer of cork or other substance is used for the transformer to sit upon. I found this comment on a transformer hum thread... Changes in acoustic buzz from a power transformer often indicate that the AC waveform is not a pure sine wave, but has harmonics. The cause of this is probably outside of your control - you may find the buzz comes and goes depending on demand on the grid. There are so many switching power supplies (including large industrial motors) that rip the **** out of a pure sinewave. Jim, thanks for your thoughts. I'll have some time later this week to look at the conditioner. A massive transformer... https://images.app.goo.gl/ZvE7yvoxRMrJcL3BA |
@jea48 , I'll try and answer all your questions. Here goes...
I leave the EquiCore on 24 hrs/day. My weekly schedule changes so when there's two or three days I won't be listening, I shut it down. To power up the system, I turn on the Equi=Core, then the panel breaker trips immediately. I used to repeat this procedure but the panel tripped every time I turned the EQ on. Now I stand at the panel with the EQ power switch in the on position and retry the breaker every few seconds until resetting is successful. The 20A is a standard residential breaker. The breaker on the EQ has never tripped and the unit has always run cool. All inputs are low-current-draw components; DAC, transport, iFi reclocker, LPS with 50VA torroid, Bluesound Node. (all digital, no SMPS) Amp and preamp are on a 2nd dedicated line. I will swap in my old Brick Wall conditioner when I have a chance. Good idea. |
@jea48 Square D QO main panel, 8 space 100 amp. Going to try to have the electrician who did the install come to the house. Will call today. I was planning to open up the EquiCore before his service call.... -- Should I have the audio sources hooked up so he can test it under load? -- What type of breaker should I request he bring; a heavy duty or commercial breaker? Good idea to try the vacuum cleaner. As always, I appreciate your time. Jim S. |
@grannyring , made an appt. with the electrician. This device is highly thought of on the forums... https://avahifi.com/products/humdinger-dc-line-blocker Will the very large toroid in the Equi=Core 1800 be a problem for a small device such as this? |
@jea48 Thanks for the transformer wiring info. I'd like to keep you updated if you don't mind. Electrician appt. is Tuesday; my service order states to inspect panel and subpanel, replace the subpanel breaker, and inspect/service the Equi=Core. I pulled the EQ out of service and will pop the top this weekend. I have a Brick Wall passive conditioner in the circuit running digital devices, no issues. But now I'm hearing hum from the power transformer in my Atma-sphere amp. It uses the second dedicated circuit from subpanel with my preamp. I'll have to check with Ralph, the amp is supposed to have a DC blocker built in. Preamp is Audio Note using their large EI transformer. This leads me to the question; can DC offset be measured by the electrician either at the service panel or the wall receptacles? |
@jea48 , this is a large electrical contractor in Philadelphia. I’ve been with them since they were a small family business. Now their prices are high and using younger techs. My guy, a master electrician who knew audio and owned a nice system is no longer with the company. He did test for DC offset and polarity when he upgraded my power 3 years ago. This morning line voltage was 124VAC on my monitor I keep in one of the duplexes. That’s high, it’s been steady at 122V for years (using a Furman conditioner with voltage display). I’ll test voltage on the amp line as you suggested. I know Ralph uses a DC blocker in his amps. Many thanks, Jim. |
@twoleftears Thanks. I'm aware of the Van Alstine as an inexpensive solution... https://avahifi.com/products/humdinger-dc-line-blocker The Isotek looks great with its ability to rebalance the AC sine wave, but it's expensive. https://www.musicdirect.com/power/IsoTek-EVO3-Syncro-Uni-Sine-Wave-Rebalancing-Unit-C19?variant=AISO... I used to own the Emotiva when I was having ground faults. I guess about five years ago, and there was never any DC on the mains. As I stated earlier, this issue is a recent occurrence, but a very real problem. |
An update and a question... The dodgy breaker fried when resetting it to power up the Equi=Core. It left a strong burning smell in the room. Of course when the electrician was here it worked fine, but he will be replacing it. So, I moved all components over to the other dedicated line and all is well. No hum from any toroid. Question: is it possible to have DC offset on only one line coming from the subpanel? A heavy gauge cable from a breaker in the main service panel feeds two 20A breakers in the subpanel. Two Romex lines (same length) take separate paths up to the receptacles. Or could there be a different issue with the one line? |
@atmasphere , replacement of the breaker solved the tripping problem. Now, I should add that the electrician found corrosion on one leg in the meter outside due to water leakage. This will be replaced soon. Until then, the subpanel breaker was moved to the other leg which is free of corrosion. Subpanel has 2 separate 20A dedicated lines; one feeds the EquiCore/all digital, other line feeds the Atma-sphere amp and Audio Note preamp plugged into a Wiremold strip. iFi power module is inline with the preamp. |
@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. |
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. |
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. |
@jea48 Jim, thanks for responding. I'll answer as many questions as I can... Philly rowhome built in 1939, new electric inside. Since I kept you in the loop during my upgrade, I know it's all up to code. Meter socket is on the outside of the house flush against the wall. There is an overhang above the meter (extension of the kitchen) so meter always stays dry. All houses are attached with flat roofs. The pole feeds the first house on the block, then power line runs along each structure close to roof with small transformers mounted on side wall. The drop attaches from this to my weather head which looks like a square box bolted to wall. Conduit runs downward mounted with U-clamps. Only the drop wire is exposed. Conduit travels 25' down then turns under the kitchen overhang into top of meter. Outside of meter is in good condition, corrosion is on wiring and contacts inside, one leg only. Meter has heavy cable travel through exterior wall directly to service panel. This cable in good condition. Electrician says the water leak starts at the top after the drop. Appreciate the help Jim. |
OK @jea48 . I can clearly see the drip loop and it's exactly like the one in your picture. I'll need to use my binoculars to see the rest. So, I'll check that the mast clamp is below the bottom of the weather head... 6" to 12" Next, I'll look for the triplex terminations. And they should be below the weather head. Now I understand how this design keeps water out of the conduit. Will report back tomorrow. Thanks Jim! |
@jea48 Hi Jim. I had a good look at my outside power hookup. There are 3 lines from the pole that run parallel to all the rowhomes; 2 heavy gauge, one thin cable. They are mounted to the rear wall and extend about 15" outward and 12" below the square weatherhead. The service drop consists of two black cables and one white. The drop is U-shaped but the black cables enter the side of the weatherhead and terminate inside. They are horizontal at the point of entry. The white cable hookup looks like your diagram and enters the bottom of the box. I'm awaiting your reaction to these findings. Thanks. |
@jea48 I have no idea what you have.... No Idea.... Has to be really old though.It is very old. This is an old neighborhood which used to have blackouts during storms. We finally got new transformers on the poles. Power is stable and higher now, 122-124VAC. Nothing stops the rain from entering the box. The black cables from the drop make a 90° turn and enter through 2 holes on the exposed side. The white neutral enters through the bottom and keeps a perfect U- shape. What's interesting is the electrician knew exactly where the water leak was. I was looking at the meter and he said no, it comes from up there. I'm going to take pics. I'll try and post them for you over the weekend. The box is surface mounted and looks like steel, about 6" x 4". The conduit drops out of the bottom and is very weathered looking; really beat up. I'm going to check out the hookups on some other homes. Jim, I always appreciate your help. Jim S. |
@jea48 These are pics of my service drop connection to my mains. https://ibb.co/qpQnYf5 https://ibb.co/VVzq1W5 https://ibb.co/JCsg9jj https://ibb.co/Y3ynkkq |
@jea48 Jim, I'm not planning to do this work myself. There's the issue of the age of these parts plus their unknown condition. There may be multiple areas of damage to the cable run. And some of the brackets are loose or broken. I couldn't open the meter lid, but not only are the contacts corroded, the entire box needs replacement. I'll take a pic once the electrician opens it. And yes, there is stucco surrounding the cable. |
@jea48 Yes Jim, I see now that it's a cable. But isn't that a vertical conduit that is attached to the box near the roof? It's fastened to the wall by brackets and ends where the cable turns and travels to the meter? I have a 2nd contractor coming to look at it. Have you ever seen an installation like this? All the attached homes have the same hookup. |
@jea48 , I plan on having the entire outside cable run plus meter lid replaced. The cable from meter to service panel was inspected and is ok. Service panel is an older unit, the previous owner had about 80% of branch circuits replaced. It's easy to spot these...new breakers and cables. The old wiring runs to low current draw areas such as bedrooms, light fixtures. I had my electrician strip wires and organise the panel to keep an even load on each leg. I extended the service to include a subpanel with (2) 20A lines, 12/2 Romex, hospital-grade duplexes. 8' ground rod off main panel with second ground rod from subpanel. Most of the homes are grounded to plumbing. |
@uberwaltz , power company owns only the meter. Homeowner is responsible for service drop and wiring to the meter box. That means I own the box, they own the meter. Things have changed a lot for homeowners in this city. Philly also decided they're no longer responsible for trees in front of house on city property. We have to pay for pruning or removal. I could go on. Some work requires permits like roofing and an addition to house. |
JEA is responsible for everything from the incoming side of my breaker box. At least the gas company is still responsible for all lines outside and inside. Homeowner's responsibility is for the appliances unless purchased from the gas company, eg, hot water heater. I think this may be universal. |
@jea48 , At first, the electrician wrote an estimate for $2500 which included all outside replacement plus meter to panel cable. He then examined the cable from meter to panel and said it didn't need replacement, so changed amount of estimate. Service for this 2 story rowhome is 60A. Don't need a permit for inside work; electric or plumbing. For this outside job, contractor will get permit and contact power company. Building inspector is only required by mortgage company during sale of a house in Philadelphia. It was inspected when I made the purchase. It passed with the old wiring and ground to water main. |
I have an electrician coming next week to install a new service drop, 30' cable, meter lid, and the service cable to a new 100A panel. He's included cost for permits and inspection by city agency. $1900. And he'll tie in to my subpanel. He talked about eliminating harmonic distortion, so I think I found the right guy. |
@jea48 I wanted you to see the new installation. And I was wrong about conduit; code does not require it. https://ibb.co/tzhyY6B No more transformer hum. |
I decided to install a whole house surge protector; a Square D to mate with my new service panel. https://www.amazon.com/dp/B00CONA1OQ/ref=cm_sw_r_other_apa_i_x2a.EbGRB0EEQ The instructions state that a 2-pole 20 amp breaker is required. OK, fine. Now here's what I don't understand; if the surge protector has its own breaker wired to hot, neutral, ground on both phases, how is it going to absorb a spike before other circuits? Won't a surge trip other breakers as well as the surge protector? There is no point of least resistance. @jea48 Feel free to comment. |
@jea48 That's all great information; the position of the SPD relative to the main breaker and how using short wiring will clamp surge voltage. There are plenty of knock-outs available to do this correctly. Your explanation of having a low grounding electrode resistance to earth helps me understand the entire concept. Now, regarding the subpanel, why is a SPD needed? Wouldn't a surge be clamped by the SPD on the main panel? As always, I appreciate your thoughtful comments. |