Did I just cook my preamp?

P.S. I replaced the 110LP today and everything is sounding great.

Thanks for explaining all this to me, Jim, it’s much clearer to me now. I understand what you’re saying about the neutral wire being broken when the outlet was taken out of the wall. I think everything else you say is accurate to what I have observed.

 

The suggestion of using a GFCI cord seems smart to me. for now I have everything plugged into one outlet, which does not have the reverse polarity. I also got ahold of an old APC power conditioner, although that does not solve my grounding problems.

 

The idea of using a non-contact voltmeter to check for other hot ground seems like a good idea. Thank you.

https://www.homedepot.com/b/Electrical-Electrical-Cords-Extension-Cords-GFCI-Plugs/GFCI-Outlets/N-5yc1vZcgerZ1z0p5yb

FWIW.

The OP can not take the chance of changing the wall outlet to a GFCI duplex outlet.   No way...

The OP could lose the power to the outlet just like the dead one that is now blanked off.

There is a very good chance the outlet is used as a feed through box. Circuit in,  circuit out. Four old rubber cloth covered wires. Chances of moving the old  conductors around, removing the old outlet, and wiring the new GFCI outlet without the old brittle insulation falling off at the steel cable support bracket or breaking falling off the wires at the BX steel armor are slim to none. Or the wires just breaking off at the support bracket from disturbing them.

Not only the outlet the electrician in trying to install the GFCI outlet in, how many other outlets could/will lose power in the process?

Not necessarily a problem, a box extension would need to be installed for the GFCI outlet because of the shallow depth of the switch box.

That’s why I suggested a plug-in type 15 amp GFCI.    

 

Just a gentle reminder that you are allowed to use  GFCI outlet where there is no real ground.  If you have an old house and want to connect 3 prong outlets this is the only safe way besides actually getting a live ground.

Not ideal but much better than using a 3 prong outlet to fake it.

 

@obarrett 

Here is a photo of an old 3 wire rubber/cloth covered wire, steel armored BX cable.

https://i.sstatic.net/pvjp6.jpg

I assume the outlet box that is now blanked off was the Hot 120Vac ground contact duplex receptacle outlet. I hope the electrician taped off or put wire nuts on the two conductors before he blanked off the outlet box. The outlet was the end of a branch circuit with several other wall outlets, and more than likely ceiling light fixture(s) a head of it.

I would suggest you buy this pair of voltage testers and check all the rest of the wall outlets in your apartment.

https://www.homedepot.com/p/Klein-Tools-Digital-Non-Contact-Voltage-and-GFCI-Receptacle-Test-Kit-NCVT1PKIT/323310181?source=shoppingads&locale=en-US&gStoreCode=2115&gQT=1

Use the non contact voltage tester to check for a Hot 120Vac ground contact. Any of those outlets are a possible electrical shock hazard. Put a piece of tape over the outlet so you will remember not to use it/them.

You might consider something like this to plug a power strip(s) into to feed all of your audio equipment. Feed everything from one duplex receptacle wall outlet. The total combined load amps of all the connected audio equipment is around 3 or 4 amps.

https://www.homedepot.com/b/Electrical-Electrical-Cords-Extension-Cords-GFCI-Plugs/GFCI-Outlets/N-5yc1vZcgerZ1z0p5yb

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@obarrett Said:

One, there was actually only one wire feeding this outlet. The wire on the left side of the receptacle was connected to nothing.

Not Quite...

The wire broke when the electrician pulled the outlet and wire out of the box.

Electrical copper wire in the old days was Hard Draw. Repeated bending of a sharp bent wire and straightening out the wire then bending the wire again could/will cause the wire to break at the sharp bend point. The more the sharp bend is bent the harder and brittle the wire gets.

The original wiring method used was not kind to the hard drawn copper wire. The wires were sharply bent 90 degrees coming out of the hole of the wire clamp. From the git go, not good. Even a sharper bend over 90 degrees when the original two wire outlet was made up on the two wires and pushed back into the shallow box.

At least one new outlet was installed to the box. Every time the wire was straightened an re-bent it got harder, more brittle.That’s what hard drawn wire does. The second outlet change may have cause a stress crack in the wire at the sharp bend. When the electrician pulled the outlet and wire out of the box it broke.

It takes two to tangle. It take both, the Hot and Neutral, to make the Light Bulb light.

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What is Hard-Drawn Copper Wire?

Hard-drawn copper is bare copper wire that hasn’t had heat applied to it after it has completed the drawing process through the dies. The more times the wire is pulled through a die, the more “work hardened” it becomes. After a certain point, the wire becomes brittle and could break due to stress.

@obarrett Said:

In the second photo you can see a metal plate; the building super removed that. Behind that was a metal cylinder, inside it was the wire. He pulled it up a few inches and cut it away to reveal a second wire.

That is steel armored BX cable.  about 3/8 inch in diameter.

He pulled it up a few inches and cut it away to reveal a second wire. So my understanding is that the neutral wire was lost down in this metal cylinder. He then insulated both wires by wrapping them individually in electrical tape and then rewired the outlet with these wires.

So my understanding is that the neutral wire was lost down in this metal cylinder.

No... Your photo(s) clearly show the end of the broken wire. I could see the end of the broken copper wire. The break was at the sharp 90 degree plus bend.

He probably was able to pull a few inches of the BX armored cable out of the box and cut off the armor off enough exposing enough of the neutral wire.

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The receptacle is mounted in metal conduit as you predicted, which I presume is grounded.

Flexible BX steel armored cable. The steel armor of the BX cable back when the building was built and wired was not designed, manufactured, for use as an EGC. Nor were the BX box connectors. You may or not read continuity on the steel armored cable but that doesn’t say what its fault current conductivity is. Treat any grounded outlet in the apartment like there is not an EGC.

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It’s clear to me that the building is wired illegally and that the management has no desire to rectify it

It was wired to code when it was built.

New York City pretty much writes their own Electrical Code. Going from memory they start with NEC but they delete what ever the want. Re-write what ever they want.  Add what ever they want. My understanding Romex, NM, sheathed cable is not allowed any where in the NYC Limits.

I have to consider how to handle this to minimize the risk to myself and other residents.

Was you able to find out the manufacturer of the electrical panel? Good chance the branch circuit wiring in the building is original. Yours is... More than likely so is the electrical panels. Get the manufacturers name if you can.

It may not be worth the Fight... If you do not feel safe living there now you might want to start looking for another apartment. Just a guess, the Landlord will let you break the lease. He probably doesn't want a fight either. Though he probably has more money and government connections than you have.

Jim

 

Hi Jim,

A few things in response to your comments.

One, there was actually only one wire feeding this outlet. The wire on the left side of the receptacle was connected to nothing. Maybe it was making contact to the metal conduit, I’m not sure. In the second photo you can see a metal plate; the building super removed that. Behind that was a metal cylinder, inside it was the wire. He pulled it up a few inches and cut it away to reveal a second wire. So my understanding is that the neutral wire was lost down in this metal cylinder. He then insulated both wires by wrapping them individually in electrical tape and then rewired the outlet with these wires. I’m not sure he installed a ground or what he did with the ground. The receptacle is mounted in metal conduit as you predicted, which I presume is grounded. I don’t think he is actually a professional electrician. The only ‘electrician’ tools he carried was an outlet tester the kind you can get off Amazon.

After rewiring the outlet in this way he tested it with his tool and it failed that test (whatever it was). He then said the wiring in that side of the room must be messed up and we agreed we’d just cover that outlet up and not use it. He gave me no real explanation of what the wiring is or what might be wrong. He communicates very poorly.

The wiring clearly looked cloth covered. Correct, I saw no jumper whatsoever. Only that wall is made of brick. The others are plaster or whatever it’s called.

It’s clear to me that the building is wired illegally and that the management has no desire to rectify it. I have to consider how to handle this to minimize the risk to myself and other residents.

@obarrett 

Correction: Edit:

Did the electrician say what type of branch circuit wiring it is? It could be BX steel armored cable. It probably comes through a hole in the back of the box and the clamp holds it in place. In the third photo I think I can see the cut end of the armor.

I looked again at the photos this morning. I am not sure that is the end of a steel armored BX cable. The empty hole in the clamp beside the one with the wires  appears to have a raised ring as well.

Also I do not think the conductors enter from the back of the box. The empty hole in the clamp shows the back of the box solid, no hole, or knock out.

I think the wiring could be old, really old, cloth covered NM cable with rubber/cloth insulation. The cable enters the box from the bottom.

What type of old wiring did the electrician say it is?

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Old rubber cloth covered insulated copper wire. This is why I advise a non electrician do not pull an outlet out of a wall or ceiling box in a really old apartment building, or an old house. 

The building Landlord has mess. An expensive mess. And more than likely the whole building’s wiring is in the same shape. 

Just a guess the electrician didn’t find a bootleg ground jumper wire on the neutral contact side terminal screw to equipment ground terminal screw on the Hot / neutral reversed polarity outlet. (outlet 1.)

I doubt he found a jumper on any of the outlets. The rubber/cloth insulation deteriorated over the years causing the bared copper wire to contact the wire support bracket. There was a 50/50 chance whether the Hot wire or the neutral wire faulted to the steel bracket / box. It’s kind of amazing that both didn’t fault to the box. Dead short.

Neutral fault to the box it’s an earth grounded box. Hot fault to box, a HOT 120Vac to ground box.

The odds are good that there are other outlets in the apartment the electrical wiring is in the same condition

Did the electrician say what type of branch circuit wiring it is? It could be BX steel armored cable. It probably comes through a hole in the back of the box and the clamp holds it in place. In the third picture I thing I can see the cut end of the armor.

 I see brick on walls in your photos. Just a guess the building is constructed of brick. ???

Did the electrician say what wiring method he will use to rewire the apartment? The only thing I can see is install surface mount Wiremold.

Wiremold steel raceway. 500 / 700 series   Start on page 47.  

I’m really curious, find out who manufactured the electrical panel that feeds your apartment. 

 .

P.S. it’s hard to make good contact with the radiator ground. The conducting part is only a small little band in the knob. That’s why the reading is unstable in the video.

Yes, I watched the video. I should get one of those no contact voltimeters, they’re $10 and apparently can detect a hot ground.

some photos from today

 

@obarrett 

https://youtube.com/shorts/t1jazBAT3M4?si=uweJOKoK0xRxrYDH

In your video, when you measured for voltage from the receptacle ground contact to the heat radiator the test probe connection to the receptacle ground contact was poor. The 120Vac reading was not a solid contact connection.

You should have used the OEM power cord ground. Insert the mm probe into the center ground contact. That also frees up your hand and you can focus your eyes on the probe connection to the radiator valve and the meter.

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WARNING: I hope you saved the plastic outlet cover plate you removed from the receptacle. When you remove the 2 to 6 outlet extender everything metal you see is HOT 120Vac to anything grounded. Don’t put your body between them.

** EDIT: On second thought. Don’t remove this one. Just leave it be.

.

Also in case you haven’t thought of it. You are going to have to move the speakers and audio equipment out of area the electrician will be working. Take some pictures first of the equipment where it normally is sitting. Just in case he asks.

The Electrician needs a minimum of 3ft working space in front of the wall outlets. The more the better. A happy Electrician is a productive Electrician.

 

Did you watch this video?   Reverse Polarity Bootleg Ground Testing 

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The deductible is too high, the v2 of the 110LP new is only $600 and renter’s insurance would give only the actual/market value of the used one I have, which is considerably less than $600.

it’s not really a problem, I’m just grateful to be alive. If I had touched the tone arm of my turntable at the same time as I was touching my CD player, I would’ve died, even if both were turned off

@obarrett , I don't suppose you have renter's insurance?

Yes I’m going to replace them with power strips and I’ve obviously stopped plugging anything with three prongs in there. As for the landlord, he’s sent someone to fix it, but he seems unwilling to replace the preamp. He doesn’t really seem to understand what voltage is or even what a ground is. I will try to get the super to convince him of the significance but I have little hope. I can tell him this stuff about electrocution, but he will just say that he’s ‘never had a problem.’

I spoke to the landlord/my point of contact for the management company yesterday. He repeatedly told me he ‘never had any trouble with the electricity’ in my apartment until now. I don’t think I can make him understand just how serious this is.

Sure you can. You can easily show him, with your multi-meter.

The ground contact is Hot 120Vac to the heat radiator.

 

My goodness it’s 120Vac on both settings. It is a hot ground. That’s so disturbing. Someone could easily have died and I’m surprised someone hasn’t yet.

.

If you have any problem with him just mention you could have been electrocuted if you had touched the radiator with one hand and the HOT 120Vac Amplifier metal case with the other hand. electrocuted, dead.

Don’t forget to remove all of those 2 to 6 power receptacle extenders.

I suggest you try another test. Plug an OEM power cord into outlet 1. Insert one of the test lead probes into the IEC female ground contact. 

Turn mm to V and touch the other test lead probe to a bared (unpainted) metal place on the heat radiator. You can also use the LoZ setting on the mm as well.

My goodness it’s 120Vac on both settings. It is a hot ground. That’s so disturbing. Someone could easily have died and I’m surprised someone hasn’t yet.

I spoke to the landlord/my point of contact for the management company yesterday. He repeatedly told me he ‘never had any trouble with the electricity’ in my apartment until now. I don’t think I can make him understand just how serious this is.

The building super claims to be an electrician and he’s supposed to work on it tomorrow. When he opens it up I’ll have a look.

here is a video documenting it: https://youtube.com/shorts/t1jazBAT3M4?si=uweJOKoK0xRxrYDH

@obarrett 

I sent you a PM.

Click on the two Web Links. Especially  the Reverse Polarity Bootleg Ground Testing Video.

Just in case the electrician only uses a plug in circuit tester and says they look Ok to him.

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.         04-01-2025 at 01:11am

Here is a photo of a two wire old rubber cloth covered conductors Bootleg grounded outlet . The wiring is really old. pre-Thermoplastic, PVC, insulated wire. PVC Thermoplastic insulation is really old too. THHN/THWN replaced it, going from memory, in the early 1970s.

Here is good video on Bootleg ground wired outlets. (FYI, a bootleg ground is a NEC code violation. Always has been)

Reverse Polarity Bootleg Ground Testing

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It’s fine. It’s Grandfathered in.

That’s a relief, @jea48 .  As long as I am not living in a potential electric chair or an incinerator  I can live with it.  I was going through in my mind what I was thinking I was going to have to do to run replacement circuits for replacement duplexes, and I wasn’t liking it, but time is one thing that I have enough of, so if I had some kind of bootleg set up I wasn’t understanding, I was going to get started on it.

Once again and as always, I thank you for the education.

How kosher is this set up that I have?

It’s fine. It’s Grandfathered in.

 

I put in were wired correctly (from duplex back to the panel, black/white/ground) doesn’t this mean that ground for the steel box of the duplex in question must end up back at neutral/ground bar at the main panel?

Several NEC code cycles ago NEC was changed stating branch circuit conductors shall be installed in the same raceway or cable assembly. That includes the EGC. (Equipment Grounding Conductor).

When a steel box is used the EGC shall be bonded to the box. Per NEC if the duplex receptacle is an auto grounding type a ground pigtail is not required from the EGC to the duplex receptacle. The duplex is grounded by the auto ground.

I personally still install a ground pigtail to the ground terminal screw on the duplex recept.  

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I assume the 3 wire duplex receptacle was fastened to a steel rough-in box when you used the "EZ check tool", (and with the circuit dead), you checked for continuity from the neutral contact to the green ground screw.

You are a genius, @jea48 !  Thank you much for getting back to me on this!!  To check for continuity from the white screw/white wire to the ground screw I remembered I had the outlet pulled out a bit from the steel box, so I just now did the same thing, and I must have had the screw lightly touching the box the first time.  This time, with the breaker tripped,  I made sure the outlet and hardware was completely clear of the box and, voila, NO continuity.  Then I let the screw touch lightly, and presto--continuity.  So I set it up so I had no continuity, put the EZ Check back in, flipped the breaker back to ’ON’, and the EZ check read as it should--"open ground."

That indicates the steel box is grounded. If the branch circuit wiring that was installed many years ago is only 2 wire that means a ground wire was installed at a later date. I would say, to replace a two wire outlet with a 3 wire grounding type outlet.

Many many, many NEC code edition cycles ago NEC allowed a ground wire could be installed from a steel outlet box to a metallic cold water pipe using an approved pipe clamp. For years a duplex receptacle was considered grounded when fastened to a steel grounded box. My guess that is what you have.

How kosher is this set up that I have?

Oh, and on edit:  I have  three duplex outlets for circuits I put in myself right next to the duplex that I just checked.  With all the outlets installed and breakers tripped, I do measure continuity from an equipment ground hole of the duplex in question to an equipment ground hole of the duplex outlets I put in myself.  Since I know for a fact that the duplexes I put in were wired correctly (from duplex back to the panel, black/white/ground) doesn’t this mean that ground for the steel box of the duplex in question must end up back at neutral/ground bar at the main panel?

Thanks again for getting back to me!

 

@immatthewj 

But the cheap EZ check tool says that they are correct???  With the breaker tripped and the outlet connected to both wires, I tested for continuity between the white screw with white wire and the green ground screw with NO wire and I have continuity????  Are they somehow bootlegged from inside the outlet?

I assume the 3 wire duplex receptacle was fastened to a steel rough-in box when you used the "EZ check tool", (and with the circuit dead), you checked for continuity from the neutral contact to the green ground screw.

That indicates the steel box is grounded. If the branch circuit wiring that was installed many years ago is only 2 wire that means a ground wire was installed at a later date. I would say, to replace a two wire outlet with a 3 wire grounding type outlet.

Many many, many NEC code edition cycles ago NEC allowed a ground wire could be installed from a steel outlet box to a metallic cold water pipe using an approved pipe clamp. For years a duplex receptacle was considered grounded when fastened to a steel grounded box. My guess that is what you have.

The duplex receptacle that is installed on the grounded steel rough-in box may now be an auto ground type receptacle. (One end of the Yoke of the outlet has a stainless steel clip that puts pressure on the 6/32 machine that bonds the supporting back strap to the grounded steel box. 

Years ago before the auto ground clip NEC considered the outlet was effectively grounded to the box with just the two 6/32 screws.

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@obarrett   I appreciate this educational thread and hopefully it's okay with you if I piggyback on it just a bit more.

@jea48 , you asked how many 2 hole outlets I had in the back of the house, and there are 3 per bedroom making a total of 9.

BUT:  I removed two of my "grounded" 3 hole outlets to inspect them for a bootleg ground.  The two I removed do NOT have a jumper from a neutral (white) screw to the green ground screw, but they also do not have any ground wire connected to the green ground screw. In other words, the only wires connected to those two outlets are the black wire and the white wire.  But the cheap EZ check tool says that they are correct???  With the breaker tripped and the outlet connected to both wires, I tested for continuity between the white screw with white wire and the green ground screw with NO wire and I have continuity????  Are they somehow bootlegged from inside the outlet?

Thank you for taking all of the time that you do to provide education and assistance to those of us who have a rudimentary grasp, or probably even less in my case, and struggle with the subject.  I certainly appreciate all your help over the few years I have been on A'gon.

 

@immatthewj 

Here is a photo of a two wire old rubber cloth covered conductors Bootleg grounded outlet . The wiring is really old. pre-Thermoplastic, PVC, insulated wire. PVC Thermoplastic insulation is really old too. THHN/THWN replaced it, going from memory, in the early 1970s.

Here is good video on Bootleg ground wired outlets. (FYI, a bootleg ground is a NEC code violation. Alwas has been)

Reverse Polarity Bootleg Ground Testing

Amprobe INSP-3 Wiring Inspector Circuit Tester

Price over $400.00

How many wall outlets are there in the old part of the house?

The only 100% sure way to check the outlet is look for the jumper wire. Remove the wall outlet cover plate. Good chance using a high power LED small diameter flashlight with the lighting in the room subdued you should be able to see the jumper on ground terminal side of the duplex receptacle outlet without pulling the outlet out of the wall box. (Turn off the circuit breaker at the panel if you are going to do any poking around.

Another sure way is plug in a high current load into the outlet like a hair dryer or portable vacuum cleaner. Anything that draws enough current on the branch circuit wiring to cause a voltage drop on the wiring.

First measure for AC voltage from neutral contact, (longer straight slot of the two.)  Notate the small voltage reading.

Next plug in and switch on the load. Check the voltage again from the neutral contact to the ground contact on the outlet. If the outlet is bootleg ground wired the reading will be the as the first measurement. If the measured voltage is a few to several volts lower, it is not a bootleg ground. 

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@jea48 , I tried to follow this thread but it became too complex for me to understand what was happening, so I apologize if this question was asked and answered and I missed it.  

Bootleg grounds:  now I understand what they are and the reason someone might wire an outlet with a jumper from neutral to ground in order to put a (3 hole) grounding receptacle  on a (2 hole) ungrounded circuit to make it pass the test with a real basic EZ CHECK circuit tester.  Since my house was built in early 1960s  and has (2 hole) ungrounded outlets in the back of the house and (3 hole) grounding outlets in the front, although the grounding outlets all pass the EZ CHECK circuit tester, it still seems like my house might be a candidate for those grounding outlets to be bootlegs. 

I went to google to look for a simple answer of what to look for with an AC VM to identify bootlegged and normal outlets and got drastically conflicting results from AI.

Again, I apologize if you previously covered this, but is there a way to verify with an AC VM whether a 3 hole outlet has been bootlegged or not?  I compared an outlet on a circuit that I installed myself that I KNOW is NOT bootlegged, and ground to neutral reads 0.105; then on a 3 hole outlet that was there when I bought the house and it reads 0.25.  (My meter does not have an LoZ setting.)  

Do those readings mean anything, or is the only way to know for sure to remove the older grounding outlets and visually inspect them for jumpers from neutral to ground?  I am getting the impression that there are more expensive meters that will verify whether or not a bootleg ground was used?

Thank you, and again, my apologies if I am asking a redundant question on this thread.

 

 

 

@obarrett said:

Hey Jim, the reason why I didn’t have an issue before is that I wasn’t using outlet 2 before. Everything that needed a ground was in outlet 1. Only after I moved things around could I access outlet 2.

FYI, outlet 2 has an earthed ground. Well, the mm measurement says so. A plug in circuit tester would say so. A Bolted Hot to the EGC ground fault might tell a different story.

Using outlet 1 you didn’t/don’t have a ground. The ground contact on the outlet is HOT 120Vac with reference to an earthed ground.  All the metal enclosures of the audio equipment were HOT 120Vac referenced to ground. Even audio equipment that didn’t use an earthed EGC.

The TT power cord is a 3 wire cord. When plugged into outlet 1 it fed the branch circuit HOT 120Vac to the TT IEC inlet connector EGC prong. That in turn fed HOT 120Vac to metal parts of the TT and to the tone arm ground, *(by the way the tone arm was HOT with reference to an earthed ground), to >> the phono preamp enclosure, which made all the RCA jacks outer ground shells HOT 120Vac that contaminated all the other metal enclosures through the interconnect cables signal ground conductor.

Why you never got an electrical shock or had problems with your audio system equipment? There was not an earthed ground introduced into the equation. 

So, for the same reason a bird perched on a high voltage power Line doesn’t get shocked.

Now the Squirrel is a different story. He will jump onto High voltage power Line and run down the Line without a care in the world. It’s his dismount from the high voltage power Line to the top of the metal earth grounded pole transformer is his fatal problem. If only he had jumped instead of stepped.

 

FYI, I am pretty sure the heat radiator shown in the video is earthed grounded. Had you been able to touch it with one hand, (in the summer months), and touched any of the HOT 120Vac metal enclosures of the audio equipment with the other hand there is a chance you would have been electrocuted. Therein dead.

DO NOT use outlet 1, until it is wired correctly by an electrician.

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I suggest you try another test. Plug an OEM power cord into outlet 1. Insert one of the test lead probes into the IEC female ground contact. 

Turn mm to V and touch the other test lead probe to a bared (unpainted) metal place on the heat radiator. You can also use the LoZ setting on the mm as well.

Post back the measurement.

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@obarrett 

Reverse polarity OR bootleg ground alone won't manifest until something else goes wrong. It's the combination of the two that is potentially lethal, because any grounded (3-prong cord) piece of equipment you plug into such an outlet sees its chassis, cover (and anyone who touches it) energized.

Please do post your electrician's findings. Curious now! 

Hey Jim, the reason why I didn’t have an issue before is that I wasn’t using outlet 2 before. Everything that needed a ground was in outlet 1. Only after I moved things around could I access outlet 2.

thanks again to you. Thanks also to you Devin. If I actually have a reverse polarity bootleg ground I will be so angry. You guys saved me more than money.

@obarrett said:

It seems like next I should call a professional electrician.

I should consult with a professional either way though.

I agree.

You should call the building manager or Landlord. They more than likely have their own Electrical Contractor they use for the electrical work in their buildings. You shouldn’t have to pay anything. Some of the electrical is unsafe.

FYI, I would remove the 2 to 6 outlet "converters" for the day Electrician is scheduled to come out.

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As for the measurements in your above post.

Outlet 2 (TT, subwoofer):

RL: 120Vac

LG: 0.36Vac

RG: 120Vac

The Hot / neutral polarity wiring is correct.

Hot (small slot) to ground 120Vac is correct.

Neutral to ground 0.36Vac looks good.

If it were me, I would buy one, or two if needed, descent plug strips and plug all your audio equipment into it/them plugged into this wall outlet. At least until you can get an electrician to troubleshoot and fix the electrical wiring problems.

/ / / /

Outlet 1 (amp, preamp, CDP):

RL: 120Vac

LG: 120Vac

RG: 0.09Vac

This outlet has the Hot and neutral reversed, mis wired.

Therefore LG: 120Vac Is wrong, not safe.

I would not use this outlet to feed your audio system equipment. To be honest, I can’t see how you can...

Imo, outlet 1 ground is screwed up causing the 120Vac between outlet "1" and outlet "2" equipment grounds. The wire feeding the ground contact on the outlet is actually the branch circuit HOT ungrounded conductor. It’s not a ground conductor. Good chance the branch circuit is only a 2-wire circuit for Outlet "1".

If you have a drop cord to plug into another grounded outlet, that tested correctly for Hot / neutral wiring polarity, you could confirm if it is the cause of the 120Vac measurement.

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/ / / / /

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I was about to send this post when I noticed your latest post.

@obarrett

Looking for info on the VPI Classic TT I found this YouTube video.

Note the steel plate. Apparently, the tone arm tower base is bolted to the steel grounded plate. ??? I don’t have any proof it is though. Fact, you measured continuity between the IEC inlet connector EGC and the tone arm ground lug/ ground wire.

VPI Classic Turntable

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More reading material for you.

Here is another possible example for the ground contact on the wall outlet, the TT has been plugged into,... to be Hot 120V.

Assuming everything was fine with the audio system until you decided you wanted to tweak the speaker placements.

IF by chance you unplugged the TT power cord from the wall outlet. (Or for any other reason the outlet could have been disturbed using it for other things plugged into it.)

Assuming the duplex receptacle was not grounded. (Therein two-wire branch circuit wiring. Old worn out 2 wire outlet was changed out to new 3 wire grounding outlet by a former tenant.

No wire is connected to the EGC ground terminal

Outlet opening is 1 gang flush rough-in steel switch box.

Hot and neutral are revered on the outlet. Therein the Hot conductor is connected to the neutral side terminal on the outlet. Neutral conductor is connected to the hot contact terminal screw side.

On a regular grounding type duplex receptacle, the EGC contact terminal screw is on the same side as the neutral contact terminal screw.

It is possible the duplex receptacle was not tightly fastened to the wall recessed rough-in box. Odds are it is not.

It is possible if the outlet was disturbed by, Unplugging the power cord and or plugging the cord into the outlet, the HOT neutral contact terminal side and the EGC ground terminal is now contacting the side of the steel 1 gang box. The side of the steel box is electrically energizing the ground contacts of the duplex receptacle.

This one you could safely check.

Remove the outlet plastic plate.

Once removed look at the neutral contact side of the outlet. Does it look like it is against the side of the steel box?

If yes, do you a plastic tea or milk container you can cut out a rectangular piece of the plastic? Slide it between the outlet and the steel box. You can cut a rectangular piece for the other as well.

Slightly tighten the two 6/32 screws that fasten the outlet to the box if needed.

Replace wall outlet cover.

Check the ground contact to see if it is still hot.

No need to reply to either post, unless want to..

If you have any further questions, you can always PM me using the Audiogon messaging system.

Jim

I concur, a professional electrician is definitely your next step.

It’s a detail, but since your landlord is required to pay for the electrician’s bill, you might want to give them a heads up if you haven't already.

I made the following measurements, both on V and LoZ. All the measurements were identical on both settings. I made the measurements two times: once with the 2-to-6 outlet converters on, and once with them off (accessing the bare outlets). The 2-to-6 converters made no difference in the measurements. So I make no distinction between V/LoZ or converter on or off in the below.

Let R denote the (shorter) female slot, L denote the (longer) female slot, G denote the ECG which sits below in the middle.

Outlet 1 (amp, preamp, CDP):

RL: 120Vac

LG: 120Vac

RG: 0.09Vac

Outlet 2 (TT, subwoofer):

RL: 120Vac

LG: 0.36Vac

RG: 120Vac

Now I took a 3-prong power cord, first from the CDP, next from the TT, and plugged into Outlet 1. I used two different cords to ensure one of the cords isn’t the problem. I plugged one MM lead into the ground of the other end of the power cord, and the other lead into the ECG of Outlet 2, and registered 120Vac on V and LoZ.

There is a third outlet where no equipment is attached. It’s on the same wall as Outlet 2. It’s measurements are the same as Outlet 2 and it also has 120Vac between its ground and the ground of Outlet 1.

I am not really following from the recent messages if there are additional tests I should run. It seems like next I should call a professional electrician.

From reading about reverse-polarity bootleg ground, it seems too lethal to be the source of the issue. I should consult with a professional either way though.

Thanks again for all your help.

 

I've looked at different scenarios for how the equipment ground could be Hot to a known EGC ground and the test with the mm would be flawed.

The most common instance is when an equipment ground is not present at the outlet box. Therein a two-wire branch circuit wiring. A homeowner replaces a two-wire duplex receptacle with a three-wire grounding type duplex receptacle. He wants a ground, so he installs a jumper wire from the neutral terminal on the receptacle and connects it to the safety equipment ground terminal. Called a Bootleg ground. Very Dangerous! It doesn't matter if a plug-in circuit tester is used, or a digital multi-meter is used it will show the presence of a ground. 

One danger with a Bootleg ground is if the Hot and neutral conductors are reversed on the duplex receptacle. That's not good... The ground contact of the outlet will be HOT!

Bootleg ground and reverse polarity, isn't that exactly what I said?

 

@obarrett 

I believe I have a way to check the duplex receptacle outlet the TT is plugged into. 

I'll post it later.

For now, hopefully for the last test, the solution would be to use another EGC grounded outlet. Like the subwoofer receptacle. I don't want you to use the CDP receptacle though, for the test. The CDP, I believe, because it uses the EGC is grounding all the non EGC equipment. It was providing the return path for hot to EGC faulted circuit.

The properly EGC grounded TT, (Which I don't think is right), will do the same.

(FWIW I doubt the CDP signal ground is directly connect to the EGC grounded CDP chassis. Just a guess the signal ground is in series with around a 10ohm resistor. This helps prevent ground loops, hum.

As for the TT EGC connected to the tone arm, I would contact the VPI support on that. That makes no sense to me.

Post back the results.

.

@obarrett 

I'm not sure preforming the same test for checking the wall outlet the TT plugs into for reversed Hot / neutral wiring connection to the duplex receptacle outlet and to check for the presence of an EGC will work in this situation. Don't see a receptacle Hot equipment very often.

I've looked at different scenarios for how the equipment ground could be Hot to a known EGC ground and the test with the mm would be flawed.

The most common instance is when an equipment ground is not present at the outlet box. Therein a two-wire branch circuit wiring. A homeowner replaces a two-wire duplex receptacle with a three-wire grounding type duplex receptacle. He wants a ground, so he installs a jumper wire from the neutral terminal on the receptacle and connects it to the safety equipment ground terminal. Called a Bootleg ground. Very Dangerous! It doesn't matter if a plug-in circuit tester is used, or a digital multi-meter is used it will show the presence of a ground. 

One danger with a Bootleg ground is if the Hot and neutral conductors are reversed on the duplex receptacle. That's not good... The ground contact of the outlet will be HOT!

Is that what you have? Maybe, maybe not. You measured two different voltages in an earlier post. On V 121Vac and 68.9Vac on the LoZ setting. For that to happen with a bootleg ground there would have to be a poor and or corroded connection. The high megohm internal circuit of the mm V setting won't add any load to across the high megohm Voltmeter Like the LoZ setting will. Could that be the case. Maybe. But the only true way would be to pull the outlet out of the box aways for a look.

I cannot advise you to do so.

First, you are not the owner of the building.

Second, the breaker feeding the outlet would have to be turn off. And verified 100% it is dead.

Third, and very important reason you said the building is old. Hard telling what type insulation covering was used on the branch circuit wiring. If really old wiring it could rubber and cloth insulation. That stuff gets old the rubber gets really hard and brittle. It doesn't like to be disturbed.

It's time to call building Maintenace. A hot safety ground is definitely electrically dangerous. A reversed hot and neutral on an outlet is also electrically dangerous.

 

 

 

I haven’t yet had the chance to do the tests you suggested in your last post @jea48

I just want to mention that @jea48 ’s advice, contrary to the statements of @erik_squires and @devinplombier , has been essential to understanding what’s going on. I’m inexperienced so I make many mistakes and my messages have been confusing at times, but I don’t see the need to come in to this thread and criticize @jea48 for providing the only instructions that have advanced my understanding of what is a dangerous situation.

regardding LoZ on my MM: without this I’d be thinking that the SMPS has 48Vac on the sleeve which is what the reading was on V and which is factually false.

@obarrett Said:

There is continuity from the ground prong of the TT to the tone arm ground lug. No continuity from either of the other two prongs of the TT.

OK

.

I attached one three prong power cord to the outlet where the amp/preamp/CDP are connected and then the other to the outlet where the TT is plugged in. I turned mm to V/LoZ, attached one lead to the ground of one, the other to the ground of the other. 120Vac.

IF true that indicates the wall outlet the TT is plugged into has a Hot equipment ground contact at the receptacle. (At this point there is not an internal Hot fault in the TT)

Before I go any farther... Test the receptacle as you have the others for the correct AC hot and neutral connections polarity on the receptacle outlet and from the Hot to the equipment ground contact. EDIT. Use both the V and LoZ mm settings.

Is the Electrical panel for your outlets in your apartment? If not do you have access to where it is located?

.

Do you still measure 120V between your two grounds when your DMM is set to standard AC voltage mode?

Yes I measure 120Vac across the grounds of the two outlets in V AC mode on the MM. well, to be clear, both outlets have 2-to-6 outlet converters sitting on top of them and I’ve connected a three prong power cord to each. So there are other things to check.

@obarrett 

Not criticizing, just outlining a simple, safe protocol. 

A couple things though: 

- Stop using LoZ mode. It is dysfunctional in your particular meter, and in any event it is not appropriate in this situation.

- Do you still measure 120V between your two grounds when your DMM is set to standard AC voltage mode?

- If so, you may be looking at a bootleg ground AND reverse polarity at one of the outlets. Unusual but lethal.

- If that were the case though, it's likely been there for much longer and would have manifested in the past.

But if that is in fact the issue, it is super dangerous.

@devinplombier said:

This thread has become surreal.

.

devinplombier post:

446 posts

03-29-2025 at 11:48pm

In response @obarrett said:

isnt that it? 69Vac on LoZ is a major issue, right?

@devinplombier response:

It’s most likely a major issue with your meter. A good meter should accurately measure a hard voltage in either standard or LoZ modes.

"It’s most likely a major issue with your meter. A good meter should accurately measure a hard voltage in either standard or LoZ modes."

No, it’s not a problem with the brand-new multi-meter.

"isn’t that it? 69Vac on LoZ is a major issue, right?"

First a digital voltmeter with a LoZ circuit meter setting incorporates a load across voltmeter circuitry. That pretty much eliminates phantom, ghost, false, AC voltage measurements. I believe I read in the manual for the Klein multi-meter, (the OP bought), the load resistance is 3K ohms.

@obarrett posted this:

121Vac on V

68.9Vac on LoZ

There is a great example of how it works. The unloaded voltage reading measured 121Vac (Using the V setting on the multi-meter.)

The LoZ measurement of 68.9Vac reading indicates there in not a Bolted Hot ground fault. Bolted? A solid Hot to ground electrical fault. The LoZ 68.9VAC tell me the is a VD, (Voltage Drop), in the Hot to ground fault. Exactly what is causing VD, series resistance, I have no idea. I just know from @obarrett posted his voltage measurements it is not a Bolted Hot to ground fault.

FWIW, for troubleshooting lose or open electrical wiring circuits in the electrical field a regular multi-meter is worthless, unless it has a LoZ setting.

A regular digital voltmeter internal resistance is in the megohms.

.

There is continuity from the ground prong of the TT to the tone arm ground lug. No continuity from either of the other two prongs of the TT.

I attached one three prong power cord to the outlet where the amp/preamp/CDP are connected and then the other to the outlet where the TT is plugged in. I turned mm to V/LoZ, attached one lead to the ground of one, the other to the ground of the other. 120Vac.

so the issue is clear: there is a 120V difference between the grounds of the two outlets, which explains every measurement I’ve made as well as explaining the spark event I observed.

doesnt this mean one of these grounds is hot? If so that seems super dangerous. I’m not entirely sure how to check which one is messed up, but this is probably related to the issue of reversed polarity I observed when testing the outlets where the amp is connected to. Maybe the polarity isn’t reversed, just the ground is hot. But when I put one lead of the probe into the ground there and the other on a piece of metal which is unplugged from anything, I see only 5V on the MM.

@devinplombier i don’t understand your criticism. The issue I just diagnosed wouldn’t be caught by your five-step recipe. The eventual issue is to me quite surprising but I’m not an electrician and I don’t know how common such an issue is.

I still don’t even understand what it means that the grounds of the two different outlets have a 120Vac difference.

thanks, Jim, for all your help. Without it, I wouldn’t have caught this issue, I would have bought a new preamp and I would’ve fried that one too.

Look folks, it's simple. Watch me say it in five easy steps.

1. Disconnect all components, from the wall and from each other. 

2. Test each component for internal shorts using the continuity feature of your DMM. This is completely safe, and you can't damage any component any more than it already is.

3. If no shorts are found, take your components to a tech for further diagnosis. 

4. If a short is found, take shorted / faulty component to a tech for repair.

5. Return your defective DMM for refund.

Questions? Please do ask 🙂

This thread has become surreal.

This conversation is going a little nuts. Testing with multiple devices for this is nonsense, except maybe as a learning exercise for new techs.

You should let a tech do all of this instead but if you must, wear insulated shoes and avoid any other points of contact after the device is plugged into the wall. Touch the device ONLY with your meter. Same for the EGC. If you are holding the EGC when you touch an active AC voltage you can be electrocuted. Set up your test area so that you can reach everything, and the EGC is readily accessible for your probe before you plug anything in. If you are squirming and contorting to connect your meter you are likely to make mistakes. Use alligator leads so you can leave the ground attached without moving it.

First make sure you have a good outlet. Use a tester like this one to make sure your ground AND neutral are good. It will also measure your N-E which is important in this case. Yes, an experienced tech can do this all with a good meter but this removes a lot of guesswork.

Plug in one piece of gear at a time, connecting nothing but the power cord. Measure voltage to the EGC using LoZ. Do this from the chassis to EGC and the outer ring of the RCA connectors to the EGC. You should measure practically zero.

If you find a high voltage use a cheater plug and measure the CURRENT from the same points to the EGC. Again, current should be nearly zero, but small leakages around 10 mA are OK. This will tell you the magnitude of the short. I suspect you have a relatively high voltage with medium current (2A or so).

Please note that using a cheater plug is dangerous as it may elevate the chassis voltage. Take extra care after attaching it.

If none of these yield answers, check the voltage on the INSIDE of the RCA. Take care as it may be high especially with tube gear. It’s worth sacrificing a cheap RCA cable to do this easilly. Cut an end off and expose the inner wire for your probe.

If you suspect a tube pre/amp, you may have DC on the inner wire.  That's bad too, but also will need you to select DC on your meter.

I forgot to mention in my above post that the EGC for the TT has to be open, broken, somewhere. It could be at the wall outlet the TT is plugged into or it could be open, broken, at the other side of the TT IEC EGC ground prong inside the TT, or the point the ground wire connects to the TT itself...

Because you don’t know where it is open, broken, DON’T plug the TT grounded power cord into any other wall outlet to find out. You could really cause electrical damage to the TT 120V electrical wiring system.

If you haven’t started the continuity test I wrote in my above post there is quicker way test if the Hot conductor is faulted somehow to the tone arm ground.

Disconnect the tone arm ground wire from the phono preanp ground lug.

Plug in the TT power cord into the same wall out you had it plugged into last night.

.

Set mm to V (volts).

Measure for voltage from the EGC wall outlet you used yesterday to the tone arm ground. you should measure 121Vac.

.