Thanks for this advice. I agree with what you wrote. I bought the amplifier used and it came with a power cord without a ground. I’m going to immediately replace that power cord with a proper three prong power cord. I think that the preamp developed a short and current was definitely flowing through the interconnects into the amplifier. What a mess.
How the preamp became so suddenly hazardous is beyond me. I can’t rule out the possibility that I connected it to the power when the other end of the TT interconnects wasn’t connected. It’s hard to remember assembly details like that one years later when you’re just moving some equipment around. Nevertheless, that should NEVER cause the dangerous situation that ensued. When I connected a ground wire from the TT to the amplifier after it had been roasted by the preamp, it SPARKED. Very upsetting.
I don’t ignore the possibility that the ungrounded amplifier could be the source of the current, but the amplifier continues to function normally and doesn’t become charged unless connected to the preamp.
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Thank you all for your responses. It’s a big help to me as I’m not an expert on electromagnetism.
@jeffbij although the amp is not grounded, it functions fine with no voltage/charge unless connected to the phono preamp. When connected to phono preamp it predictably becomes dangerous.
@erik_squires as it turns out as others have pointed out, no ground pin was removed and the amp is by design ungrounded. I agree it’s dangerous. Could you elaborate on what an outlet tester would tell me?
@jea48 RR2160 amp has built in DAC and has two coax inputs. One to CD player one to bluesound node. Since this episode I’ve been listening to music off the node without problems. Thank you for pointing out the RR2160 doesn’t have a ground pin. At least one of us is paying attention, I guess. The preamp and amp are plugged into the same single duplex outlet; the TT is plugged into a different single duplex outlet but was OFF when this happened. Could you describe what information I could use a multimeter to obtain? I will get one if it will help diagnose.
yes you’re right the preamp was grounded to the tone arm.
yes the outlet cover is plastic and the plug in power supply for the photo preamp is plastic.
you asked what two metal objects I was connecting. I was connecting the interconnects from preamp OUTPUT to the analog INPUT of the TT. those inputs are near the speaker wire plugs for the right speaker. When I touched the interconnect from the preamp to the amp analog input the second time, there was a large SPARK and even some SMOKE. It created a small crater on the housing of the interconnect. Obviously extremely hazardous.
@lynn_olson @jea48 do I need a multimeter, socket tester, or both?
I had an idea which may be totally wrong but I noticed the blue light in the 110LP flickering the last couple months, and it’s connected to the circuit inside the preamp by a wire. Maybe something went wrong with that wire and it shorted to the exterior of the preamp box. It would be easy enough to check by disconnecting that wire, but first I need to get the appropriate equipment. I was going to just get a no contact voltmeter, but it seems maybe I should instead get a multimeter? Let me know what you would advise.
thank you.
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@jeffbij Yes I’m sorry I misspoke. I was connecting to the RCA input of the amp, not the TT.
@jea48 yes wired coax to router, then Ethernet from router to bluesound node. Ethernet is not shielded. Both cables pass close to the interconnects going to/from the preamp through the back of my cabinet. I made a video: https://youtu.be/dPq8B54utCw?si=o6S-uJqUXYGxfJiT.
yes, I meant analog input of my RR2160. Apologies.
spark from outer shell of RCA cable. In video I show exactly where as it left a crater in the metal casing. NOT the center pin of the interconnect.
i ordered the Klein tools MM720 you recommend. It should arrive tomorrow. Please tell me what tests I should start with and how to execute them. I’m not going to get a separate outlet tester if it can be achieved using the multimeter. Thanks for all your help.
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The CDP appears to be grounded with three pins and the power cord has three prongs. The amp is placed on top of the cdp so they are touching.
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I will test now following your instructions and report back. The subwoofer plug into the wall has three prongs but when it plugs into the subwoofer it has only two. So it’s not grounded either. I will be around for the next few hours and will send messages as I proceed through your instructions. Thanks so much.
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I just tried an additional test.
I plugged in the preamp to the wall using its SMPS.the blue light went on, off, on, off four times getting fainter then went off.
I plugged the black lead into the ground of the OEM IEC power cable. I put the MM on V. Red lead on any one of the four RCA inputs/outputs of phono stage. Same reading as in the SMPS: 48V, but when I switch to LoZ, drops to 0.128V.
i then unplugged the phono, connected it to TT via RCA Input on phono, plugged in again. Measured 49V with red lead on the shield of the interconnect plugged into the R input of the phono, which dropped to 0.14V on LoZ
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I did your test from your long post.
wall:
hot neutral 121.7V
hot ground: 122.0V
Neutral ground: 0.285V
OEM ITC:
Two females: 121.3V
female ground: 121.7V
SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):
48V on V
0.13V on LoZ
thoughts?
SMPS (red lead center, black on sleeve):
18.5V on B
0L and it beeps on LoZ
Note: this wasn’t using the outlet where everything is currently plugged in. I used a spare outlet. I can test the outlets where things are plugged in too.
and to elaborate: yes I felt current on the enclosure of the preamp. I also felt current, I believe, on the enclosure of the amp at some point. And when I connected the tone arm ground cable to the amp ground (the amp has a built in phono stage), there was also a spark. I believe current was flowing through the interconnects between phono preamp and amp, but i don’t know the source. But since all this I’ve listened to about 3 hours of music using the amp with no issues whatsoever (phono disconnected of course).
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I think I messed up on the DC measurements, i think they were AC. so let me try again:
SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):
0.6 mV DC on V
0.0 mV DC on LoZ
SMPS (red lead center, black on sleeve):
18.15 V DC on V
18 V DC on LoZ
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I tested the outlets where things were plugged in. The hot/neutral is reversed. So the hot is the longer left slot, the neutral is the shorter slot on the right. The ground appears to be functioning.
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Does the 120Vac IEC inlet connector on the back of the sub have three prongs? Therein an equipment ground prong? My bet is yes. Correct?
Yes I verified your question about subwoofer in earlier comment today. The subwoofer pins are only two even though the power cord has three prongs. So I assume it’s ungrounded. But note the CDP is grounded and the amp is sitting on top of it and connected via coaxial cable.
Was the SMPS unplugged from the 120Vac wall outlet or the power cable from the SMPS disconnected from the phono preamp? Preamp was dead?
I believe it was plugged into but I’m not confident on this. But moreover I was trying to connect the interconnects; at some point they were connected, then they were disconnected. So when I felt current on the enclosure of the amp I do not know what was connected to what.
Yes agree. But, my understanding is the SMPS was feeding power to the phono preamp at the time. Correct?
yes with 90% confidence.
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Ok I did AC again and verified the previous numbers.
SMPS (one lead in ground of OEM ITC, the other on the sleeve contact of the SMPS):
48.7 V AC on V
0.125 V AC on LoZ
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Saturday, check for voltage from the outer shell of the output RCA jack of the phono preamp to the outer shell of the analog input RCA jack on the RR2160 amp.
Should of done that to begin with...
Both units powered on.
5.5Vac on V
0.02Vac on LoZ
When you get a chance check the wall outlets the equipment plugs into for proper Hot / Neutral polarity and for equipment ground. At least you will be able to check them off your list.
I sent a lot of messages last night so perhaps you missed:
I tested the outlets where things were plugged in. The hot/neutral is reversed. So the hot is the longer left slot, the neutral is the shorter slot on the right. The ground appears to be functioning.
Explicitly, this means when I’m on V or LoZ and I go into hot/neutral I get 120Vac. When I go neutral/ground I get close to zero, and when I go neutral/hot I get ~120Vac. However, hot/neutral is reversed.
i don’t think it matters but when I plug one lead of MM into ECG and the other isn’t connected to anything I get 5V on V but it disappears of course on LoZ.
Question... Is the SMPS 120Vac plug in blades the same width or is one wider than the other? Therein polarized. If both blades are the same reverse the SMPS 180 degrees in the receptacle and perform the test for high voltage again.
the blades are the same width. For the following test I plugged the SMPS into the wall in the same configuration as it was in when the incident occurred.
I don’t know what I was thinking yesterday... I should of had you do the tests with the phono preamp connected to the SMPS. Therein the connected load. Likely a defective connected load that might be overloading the SMPS. A real world test...
ok I did this test following your 7 instructions and got the following readings:
52.5Vac on V
0.16Vac on LoZ
i know you said LoZ not necessary but I did it and again the voltage disappeared.
0 on DC on V and LoZ (I looked into ghost voltage and it seems like a purely AC phenomenon).
i was watching the blue light on the 110lp as i was doing this test and it was blinking continually. I made a video: https://youtu.be/Dcaxu_ZM6VQ?si=sj70-NxTUOHN3noQ. The blinking did NOT fade away but kept going like this faintly.
I remember last weekend when I had the preamp connected to the amp’s analog 1 input and I listened, I heard a ‘bump’ paced exactly the same as this blue light’s blink. This was as a record was playing and the preamp was connected to the TT. I heard no music just this gentle regular bump.
I’m starting to think neither component (amp or preamp) is behaving evilly on its own (although the preamp seems clearly broken), but only together there is a toxic combination. Note, I used these components together fruitfully for the last 3 or 4 years. It was only when I moved them last weekend that disaster struck. It’s also conceivable to me that the preamp was dangerous but now some circuit is shot and it’s not dangerous anymore. I’d also like to test connecting something else to the RCA input on the amp but I’m not sure I have anything I can test. Maybe my TV. As mentioned I did connect the TT directly to the phono stage of the amp last weekend and it did function normally, just was unlistenable (because of how bad the integrated phono stage is).
I’m obviously leery of connecting them again but if there’s some way to do so safely I might be willing to try. Thanks for all your help.
and yes, I’ve been listening to music off the amp using the node (am doing so right now) and it sounds great. (Hariprasad Chaurasia today.)
one more remark: when I was trying to connect the IC from the preamp out to the amp analog 1 input last weekend, the whole general area of the rear of the amp felt dangerous. It wasn’t just the rca plug. It might have also included the speaker wire which is securely seated in the amp. On this point, you saw the crater on the IC exterior in my video but I’ve been unable to see any corresponding damage to the amp. I just looked closely. It almost seemed like the spark jumped from the air and landed on the IC. I don’t know if this is possible.
@mark200mph thank you. Fortunately I can still listen to music over digital and that is what’s keeping me sane.
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I haven’t mentioned it yet. You may have damaged the analog L & R input circuitry in the RR2160 amp. The pair of RCA jacks you plugged the ICs into from the phono preamp.
This wouldn’t be a big deal if the three other RCA inputs still worked. Last weekend I connected the preamp to analog input 4 on the amp and it made the same soft bump sound. I just remembered the blue sound node also has an integrated DAC and RCA out. So if I don’t mind risking frying it I could try connecting it. Ideally I should find something cheaper, maybe my TV (which is old and I don’t use). I’ll check if it has RCA out when I get home.
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I just plugged everything into all the outlets as it was last weekend (minus the interconnects between phono and amp) and re-did the test where one lead is on preamp output, one on amp analog 1 input rca plug.
121Vac on V
68.9Vac on LoZ
0Vdc on V
isnt that it? 69Vac on LoZ is a major issue, right?
I then unplugged the grounded 3 prong power cord from the cd player and the voltage registers ~0Vac on LoZ between the RCA output on the preamp and the rca input on the amp.
both amp and preamp were on at that time.
i then turned the amp off and turned off its power switch but left it connected to the wall and the same readings were registered.
if this is the problem I think it is, I need your help to understand what the core source of the problem is and what piece of equipment is misbehaving.
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Wow, listen to this.
i unplug the preamp from power. I unplug all interconnects from preamp. I leave the grounding wire connected, which grounds the preamp to the record player tone arm. I put one lead of the multimeter in the ECG coming from the outlet where the preamp, amp, and CDP are connected, and the other lead on the RCA output of the preamp and I read 121Vac on LoZ.
I now unplug the (grounded) power cord from the turntable and do the same test (still with the ground cable attached to the preamp and the tone arm) and see 0Vac.
note: The turntable is connected to a different power outlet than the preamp and the amplifier. the turntable is off the whole time.
the building I’m in, yes it’s old (I think maybe 100 years) and I rent. I will need to test the outlets where the TT is plugged in tomorrow.
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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.
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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.
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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.
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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.
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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.
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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.
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
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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
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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.’
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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
 
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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.
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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.
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P.S. I replaced the 110LP today and everything is sounding great.
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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.
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