Did I just cook my preamp?

@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.

.

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?

 

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 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.

@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.

.

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.

.

/ / / / /

.

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

.

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