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.
This leads me to the question; can DC offset be measured by the electrician either at the service panel or the wall receptacles?
DC on the AC mains can be measured at either location. In your instance you want to measure it at the wall receptacle outlet that you are using for your audio equipment. Question is does the electrician and or electrical contractor you have hired have the test equipment to properly measure for DC voltage on the 120Vac mains. Unless the electrical contractor/electrician has a power quality analyzer meter something like this one then the answer no. https://www.fluke.com/en-us/product/electrical-testing/power-quality/437-series-ii#
A typical good quality digital multimeter (DMM) will not correctly measure for DC on the AC mains unless a low pass filter (lps) is used. The lps is connected between the 120Vac mains and the DMM. The DMM is set to auto DC Mv. I have a FLUKE 87 DMM and it cannot correctly measure for DC on the AC mains. I made a simple lps. Nothing to it. It’s of a lot cheaper than buying a power quality analyzer meter.
I don’t know how big the electrical contractor/electrician is that you have hired. I do know a few good sized electrical contractors in my area. They could easily afford to buy a $10,000 power quality analyzer meter. I doubt if any one of them has one setting on a self in the shop just setting there waiting for the next time it will be needed.
If they have a customer where they may have a power quality problem in their facility the electrical contractor hires a Power Quality Testing Company. For around $150 to $200 an hour you can hire a Power Quality Testing Company that employs qualified, certified, trained, technicians to preform the power quality testing. The testing company furnishes the electrical contractor a complete certified test report when they are finished.
Do you need to hire a Power Quality Testing Company? Probably not. I do find it odd though that the transformer in the Atma-sphere power amp is mechanically vibrating more than it normally should. It’s my understanding Ralph installs a DC blocker in all his amps that use a Toroid power transformer.
Quick test. Check/measure the AC line voltage at the duplex receptacle wall outlet with the power amp turned on. You want a conned load for the test.... A higher than normal AC voltage can cause a power transformer to buzz, mechanically vibrate, louder than normal. Normal? Voltage should be around 120V.123Vac is getting on the high side. 124Vac -125Vac and higher is definitely on the high side.... Look on the rear panel on the amp, what is the recommend nominal AC line voltage for the amp?
There are many DC blockers available, at different price points. PS Audio used to make a popular one, occasionally available used. Audio by Van Alstine, Emotiva, and Isotek all have models.
@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.
@jea48 Multimeter reading on the dedicated Atma-sphere line is 123.0V. Amp is powered up with no transformer hum. I guess I should take a reading when the amp is humming.
BTW, the digital line measured 123.8V and later dropped to 121V, so voltage is fluctuating.
Next time it hums I would walk around your place and look for anything turned on that may not always or usually be on. Once I figured out the curling iron thing I never had a problem again. Who would have guessed. Good luck.
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.
Tuffy, while the Equi=Core was humming I turned off the refrigerator and other appliances. And no dimmers in my house. I live alone so I know what devices are being used. Although I forgot to turn off the router.
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?
It can happen if a power supply sucks juice only on the positive, but not the negative cycle, on the same phase. I could also see something funky if your neutral was loose, but it wouldn't be DC.
Thanks, @erik_squires Speaking of positive and neutral, why does a balanced power conditioner have inverted polarity? I know the 120V signal is inverted into + - 60V, but shouldn’t the polarity be corrected at the output?
Those testers are very very simple devices that work well only with "normal" problems.
Chances are it looks for voltage on the neutral, and decides if it is there, that the voltage is inverted.
It doesn't know anything about balanced power. It's just very basic circuitry performing very simple IF...THEN calculations, and that is exaggerating the complexity already. :)
Why would you continue to use a defective product that can simply be eliminated? Don't ask the electrician to diagnose it. He will have no idea what is going on. I worked summers as an electrician. It is a different ball game than electronics.
I don't believe it's defective and I only wanted him to test connections, which he said he can't work on ancillary equipment. I opened it up and inspected it.
@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.
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.
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.
Wow, I am really sorry and surprised to hear that you have to pay for that. Is your utility not willing to share the expense with you? Perhaps they are blaming the maintenance for the whole problem, but that does not really seem fair to me. Its equipment should be able to withstand weather.
Are you in the US? If so, you may want to consider filing a complaint with your state’s Board of Public Utilities (or whatever its equivalent is) to recover some or all of your costs. It might be worth the effort.
I know from experience that my electric utility is responsible for the meter and the meter pan. I do have underground electric service, so that may explain the difference.
With an aerial drop, I think the utility might be able to claim that its responsibility ends at the drop, not the meter. In that event, maybe your homeowner's insurance might provide some coverage?
. There’s a water leak in the conduit from my roof down to the meter and the seal into the pan has worn away.
Is the meter socket on the outside of the house? Is the meter socket surface mounted on the outside of the house? OR Is the meter socket recessed into the out wall of the structure? If the house was built back in the 1950s or earlier is the meter socket mounted in the basement?
Looking up at the electrical service drop service entrance weather head on the roof. How is the utility company’s triplex cable supported at your house? Eye bolt in the structure? Mast clamp on the steel rigid pipe that drops down to the meter socket? At the point of attachment of the powers company’s triplex cable how far would you guess it is below the weather head where the your service drop wires come out of the weather head? Example,.... Above the weather head? Below 6", 12", 18"? Pictures. https://www.google.com/search?source=hp&ei=7GqgXu_YLML5tAaFkabwBA&q=electrical+weather+head+...
@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.
The picture shows a typical fed overhead electrical service where the meter socket and mast pipe are surface mounted. (Yes I know yours is concealed with a semi- flush mount front meter cover.)
What I want you to look at is where the power company’s triplex cable connects to the mast pipe. (May be in your case to an eye bolt).... Note in the picture the triplex is supported by an insulated mast clamp. Notice the mast clamp is below the bottom of the weather head? The point of attachment of the triplex must be below the bottom of the weather where the service conductors exit the weather head. That is a must!
Looking at the picture. Next notice the loop, (called a drip loop), in the service wires that exit the weather head that are connected to the triplex. See the drip loop? The drip loop is a must! When it rains the rain water that collects on the three wires runs to the bottom side of the loops and drips down off the wires. If the point of attachment of the triplex is above the weather head that increases that side of the loop and will cause the rain water to run up into the weather head and run down the outside of the wires inside pipe onto the termination lugs of the meter socket. (Water seeks its’ own level)
Next go outside and look at your service. Is the triplex attached to the structure above the weather head or below the weather head by around 6" to maybe 12"?
Next thing to look at closely...... Look closely how the two 240V insulated wires and the bare neutral neutral conductor of the triplex are spliced, connected, terminated, to the two black insulated conductors and the bare neutral conductor that enter the weather head. First the terminations should be below the weather head. That is must. If not if rain water can enter between the insulation and the stranded wire conductor the insulation jacket will work just like a siphon hose and the rain water will run down the inside of the insulated conductors and run out onto the lugs in the meter socket.
Next thing to look at closely...... Look closely how the two 240V insulated wires and the bare neutral conductor of the triplex are spliced, connected, terminated, to the two black insulated conductors and the bare neutral conductor that enters the weather head.
That should read:
Next thing to look at closely...... Look closely how the two 240V insulated wires and the bare neutral conductor of the triplex are spliced, connected, terminated, to the two black insulated conductors and the INSULATED neutral conductor that enters the weather head.
Sorry about that......
(Insulated neutral conductor will more than likely be black wrapped with white marking tape.)
@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.
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.
Wow.
Well, it sounds like the utility power lines are below the " square weatherhead". That’s good.....
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 drop is U-shaped but the black cables enter the side of the weatherhead and terminate inside."
weatherhead? Sounds more like a junction box. How big is the box? Just a guesstimate.
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.
I have no idea what you have.... No Idea.... Has to be really old though. What stops the rain from blowing in through the side of the box where power wires enter? I assume the box is surface mounted? Is there a conduit that drops out of the bottom of the box?
The white cable hookup looks like your diagram and enters the bottom of the box.
240V Lines enter through the side of the box, and the white neutral wire enters from the bottom of the box. Correct? Is the box made of steel? .
I have no idea what you have.... No Idea.... Has to be really old though. What stops the rain from blowing in through the side of the box where power wires enter? I assume the box is surface mounted? Is there a conduit that drops out of the bottom of the box?
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.
Your service entrance drop is a cable. It is not a conduit with wire installed in it as I imagined.
It appears to me rain water is entering between the outer sheath of the service cable and the weather proof strain relief connector on the top of the meter socket. My guess is the rubber bushing, (or possibly, depending on the age of the connector, Oakum Packing Material), that is supposed to seal the service cable and the metal connector from allowing water from entering the meter socket is shot, deteriorated, allowing water to enter.
A band aid that may stop/help from rain water from entering the connector, therein the top of the surface mounted meter socket is to apply a good quality pure silicone caulking around the service cable and the weather proof strain relief connector.
Clean the cable with a dampened dish soap and water washcloth at least a couple of inches above the top of the connector and the entire top of the screw down cap/nut of the connector. Remove any loose debris that may be laying between the cable and the inside of the connector. Rinse off the soap with a slightly water dampened clean washcloth. Repeat as necessary to remove all dirt and soap. Repeat process if needed to get all surfaces clean. Allow to completely dry several hours. Surface areas must be 100% dry.
Apply the pure silicone caulk around the cable where it enters the connector throat, opening. Make sure you force, inject, as much silicone into the top of the connector between the cable and the connector as possible.
Finish off forming the silicone product using your finger. You want the silicone caulk to cover the top nut of the connector so the water will shed down the side of the connector.
Next using your finger slightly form, taper, the silicone caulk up all around the cable. Do not leave any globed pockets for water to puddle. You want the finish product to look like cone.
(To stop the silicone from sticking to your finger, as you form it, slightly moisten the tip of your finger with water as you form the silicon.)
Looking at the picture again it looks like the back of the connector may be buried slightly in the outer stucco cement finish. Hard to really tell from looking at the picture.
If you want to get a good water tight seal you may have to chisel away some of the stucco to expose the back of the cable and the back side of the connector.
Use a small chisel and a small hammer... Take your time.... BE CAREFUL! Do not damage the outer sheath of the service 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 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 , 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.
Am I missing something here? Surely all of this should be on the electric company provider to make good and safe? Here if I was even to look at anything on the incoming side of my main panel JEA would likely have me hung, drawn and quartered!
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.
The cable from meter to service panel was inspected and is ok.
@lowrider57
Inspected by who? The city AHJ?
In my city. Any time a new electrical service is installed an electrical permit must be pulled by a licensed electrical contractor that is licensed to do electrical work in the city.
Minimum overhead fed electrical service required for a single family dwelling unit is 100 amp. Is the cable/wire rated for a service entrance rating of 100 amps? In my area, before the Utility Power Co will hook up the new electrical service the City AHJ must release the new service for a hook up.
What all was the electrical contractor/electrician that gave you a price of $2000.00 going do? Was he going to re use the old cable from the new meter socket to the existing electrical panel?
@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.
Am I missing something here? Surely all of this should be on the electric company provider to make good and safe? Here if I was even to look at anything on the incoming side of my main panel JEA would likely have me hung, drawn and quartered!
@uberwaltz
It depends where you live who owns what and who is responsible for what. In lowrider57 case he owns, is responsible for, the service drop, meter socket, and service entrance wiring from the meter socket to his electrical service panel. He is also responsible for the system grounding as well, (grounding electrode system).
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.
That sucks for lowrider. I guess my part of Florida not so bad after all then... lol. JEA is responsible for everything from the incoming side of my breaker box. Upkeep and any work required unless I was somehow to deliberately damage something. If I was then still alive......
@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. Upkeep and any work required unless I was somehow to deliberately damage something.
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.
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.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.
