Did I just cook my preamp?

@obarrett 

Odds are that your phono stage's outboard power supply has a short to ground.

Linear power supplies run hot and are generally the first component to fail.

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

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.

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.

@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.

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 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 

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!