Two receivers fried after being plugged into the same outlet

[Roboturner91]

Both early 90s Yamahas - RX-V850 and RX-770. Both displayed the same behavior - turning off about 2-3 seconds after being turned on.

To make a short story long, I recently changed the rooms my house (old house, built in 1930s). Put my two sons in the same bedroom, moved my home office into the now-empty younger kid's bedroom.

Set up my stereo, enjoyed it a couple days, then poof. Receiver (RX-V850) went dead. I brought it to a repair shop, plugged my backup receiver (RX-770) into the system. Same thing. Worked for a couple days, then poof. It's dead now too. Now I'm suspicious it's the power outlet so I checked that out.

The outlet I had plugged both these receivers into reads hot/neutral reversed on my outlet tester. I plugged the second receiver into a known good outlet and it still doesn't work. I don't have the first one since I brought it to the shop but I suspect that would be the case for it as well.

Is it safe to say this outlet killed my receivers? I didn't think reversed polarity wiring was all that dangerous. I'm going to replace the outlet and hopefully my receiver can be fixed.

 

[toxcrusadr]

Do the receivers have polarized plugs? If not then it shouldn't matter at all.

If they do, it may or may not matter.

Was this outlet or circuit rewired recently or how long has it been like this?

Have you checked the voltage on the outlet?

 

[John James]

Have you asked your sons if they like bunking together?

A little sabotage?

(Joking)

 

[woodj]

The outlet I had plugged both these receivers into reads hot/neutral reversed on my outlet tester.

This could indicate partial loss of neutral in that circuit.

Do the receivers have polarized plugs? If not then it shouldn't matter at all.

If they do, it may or may not matter.

Was this outlet or circuit rewired recently or how long has it been like this?

Have you checked the voltage on the outlet?

Good idea; be careful to set the voltage scale high enough on the initial reading so you do not damage the meter

 

[toxcrusadr]

Probably crazy but I was thinking that somehow two hot legs could have got in there instead of a hot and neutral making the outlet 240V. But anything else on that circuit would feel the burn too.

 

[Roboturner91]

Do the receivers have polarized plugs? If not then it shouldn't matter at all.

If they do, it may or may not matter.

Was this outlet or circuit rewired recently or how long has it been like this?

Have you checked the voltage on the outlet?

The house was built in the 30s. I have no idea of the history of it before I moved in....it's not been touched since I moved in but it is the old two-slot outlet. I changed all the other ones in the house, which all test out fine. I just never got around to this one room because it wasn't really needed.

I haven't tested the voltage of the outlet. I have a multimeter though. What should it be?

 

[Roboturner91]

Probably crazy but I was thinking that somehow two hot legs could have got in there instead of a hot and neutral making the outlet 240V. But anything else on that circuit would feel the burn too.

I had a CD player, turntable and equalizer plugged into the same outlet, all are fine. That's what really baffles me. I've also charged my phone on that outlet with no issues.

 

[Roboturner91]

Have you asked your sons if they like bunking together?

A little sabotage?

(Joking)

ha! No, they begged to sleep in the same room. They are borderline obsessed with each other.

 

[toxcrusadr]

Well it's very doubtful there's 240 in there but set your meter to 250VAC or higher (unless it is autoranging). It should read somewhere around 115-125V. If it had two hot legs it would read 220-240V.

If it's an old style 2-slot outlet, it would not be polarized (i.e. one slot smaller than the other indicating the 'hot' side). How did your tester would know the hot and neutral were swapped in the first place. Did it matter which was which when the plugs weren't polarized anyway? Maybe someone older/smarter than me will know what the convention was supposed to be (if there was one) before polarized outlets.

[Edit: Upon searching the web it's clear that there are polarized outlets with no ground. Is that what you have?

 

[Roboturner91]

Well it's very doubtful there's 240 in there but set your meter to 250VAC or higher (unless it is autoranging). It should read somewhere around 115-125V. If it had two hot legs it would read 220-240V.

If it's an old style 2-slot outlet, it would not be polarized (i.e. one slot smaller than the other indicating the 'hot' side). How did your tester would know the hot and neutral were swapped in the first place. Did it matter which was which when the plugs weren't polarized anyway? Maybe someone older/smarter than me will know what the convention was supposed to be (if there was one) before polarized outlets.

Probably should've mentioned this, I had one of those 2 prong to 3 prong adapters going on.

Just tested the outlet with my multimeter, it goes from 122 to 125, which if I understand right, is on the high side of OK.

 

[Beemerdoc]

The neutral wire (white) should go to the silver colored screw on the plug, and the hot wire (usually black or red) will go to the brass colored screw.
Reversed polarity could damage some things, but only if they have a polarized plug (one spade larger than the other) typically.

 

[toxcrusadr]

Your voltage is OK then. Power companies vary and sometimes the voltage goes up and down during the day.

 

[Roboturner91]

[Edit: Upon searching the web it's clear that there are polarized outlets with no ground. Is that what you have?

Yes. Both slots are "T" shaped with one slightly smaller than the other.

I'll have to shut down the power and pull the outlet to confirm but I'm assuming it was wired backwards.

I can put in a new outlet, that's not hard. I just don't understand how this could've blown up the receivers and nothing else on that same line. The outlet my computer is on also reads hot/neutral reverse but obviously the computer is fine or I wouldn't be posting here right now.

 

[The Fuxtor]

Maybe your speaker wires are touching somewhere?? Possibly fried the outputs??

 

[Roboturner91]

Maybe your speaker wires are touching somewhere?? Possibly fried the outputs??

Unless the problem is somehow inside the speaker, no. I haven't had the chance to take the speakers apart but I tested them about 6 months ago and they were fine.

 

[toxcrusadr]

I don't think we asked whether the plugs on those receivers are polarized or not.

I wouldn't think it would matter to swap leads, if it did the rig wouldn't play at all, but you said the first one played for a couple days. Polarized plugs were basically to limit the amount of circuitry with voltage on it when not powered up, and to prevent voltages in dangerous places (like the threads of a light socket vs. the center button). It shouldn't matter in terms of operating the unit.

Any word from the shop on what's wrong with the first one?

Did you check fuses on the receiver(s)? It would be odd to have two blow in succession randomly, but random stuff happens.

 

[Roboturner91]

Yeah, both receivers were made in 1993, they both have polarized plugs. I have not heard from the shop yet. He said it could be 3-4 days.

 

[Roboturner91]

I tested both speakers, woofers both measured between 8 and 9 ohms, tweeters were about the same which is normal. I do not know how to test crossovers but nothing was exploded in there and everything seemed solidly connected to the board.

 

[toxcrusadr]

What else is on that circuit?

Any electrical storms lately?

 

[N8Nagel]

Still check for a loose neutral. Monitor the voltage at the outlet then turn on a hair dryer or something. If the voltage goes up or down more than a couple volts there is a problem