Hypex faulty power switch, is this issue common?

[archerious]

I ordered a Audiophonics MPA-S250NC (Hypex NC252), but when it arrived I noticed whether the power switch was on or off, the unit still powered on and played music.

Had a loud audible hum as well.

Thought nothing of it, until I went to move it from my office to my listening room and it shocked me!

Is this issue common with Hypex power switches?

Audiophonics is going to allow me to return it, and their customer service has been great, just kind of concerned about my options going forward.

 

[March Audio]

This is clearly a fault with the switch or incorrect wiring if it doesn't turn on / off or hums.

Our implementation is unique in that we have a control board and touch switch which activates the amp module from standby, we don't use a typical mechanical push switch.

What's very much more concerning is that it shocked you. Before you send it back my advice is to take the lid off and take some photos of the internal wiring. Post them on the forum for people to comment. It's difficult for me to publicly comment as I just get criticised for being a manufacturer trying to damage my competitors.

*If* it turns out that there is a problem with the wiring then people need to be aware so they can check their own audiophonics products for safety.

 

[archerious]

This is clearly a fault with the switch or incorrect wiring if it doesn't turn on / off or hums.

Our implementation is unique in that we have a control board and touch switch which activates the amp module from standby, we don't use a typical mechanical push switch.

What's very much more concerning is that it shocked you. Before you send it back my advice is to take the lid off and take some photos of the internal wiring. Post them on the forum for people to comment. It's difficult for me to publicly comment as I just get criticised for being a manufacturer trying to damage my competitors.

If it turns out that there is a problem with the wiring then people need to be aware so they can check their own audiophonics products for safety.

I am worried if I open it up they'll blame me for the issue tbh.

Had bad experiences with the industry I work in being like that (Aruba and Meraki enterprise networking gear).

 

[Doodski]

I am worried if I open it up they'll blame me for the issue tbh.

Had bad experiences with the industry I work in being like that (Aruba and Meraki enterprise networking gear).

Are you in the USA? I thought the USA has laws protecting the consumer from the sort of thing you are concerned about if you open it.

 

[archerious]

Are you in the USA? I thought the USA has laws protecting the consumer from the sort of thing you are concerned about if you open it.

I got a warranty stick void if opened on my Meraki MR36

 

[Kal Rubinson]

Is this issue common with Hypex power switches?

This is not a Hypex power switch. This is a switch that Audiophonics assembled in a chassis with some Hypex modules.

 

[archerious]

This is not a Hypex power switch. This is a switch that Audiophonics assembled in a chassis with some Hypex modules.

Thank you for clarifying, pardon my ignorance. I didn't realize it didn't come from hypex.

 

[Doodski]

I got a warranty stick void if opened on my Meraki MR36

It's your property and you are not modifying anything nor servicing it. I don't think there's a judge in a developed nation that will not support you on that basis. I used to take it (the bull) and not complain and then I took up civil court a couple of times and they backed off real fast. Just the thought of a consumer opening a file in their hometown makes them back off because they have to attend wherever you open the case file.

 

[archerious]

It's your property and you are not modifying anything nor servicing it. I don't think there's a judge in a developed nation that will not support you on that basis. I used to take it (the bull) and not complain and then I took up civil court a couple of times and they backed off real fast. Just the thought of a consumer opening a file in their hometown makes them back off because they have to attend wherever you open the case file.

Good point, plus I'm curious what's wrong with it myself, bet the people on this forum could tell from a glance.

I'll look for a hexagon shaped screwdriver, I think I own one.

 

[wwenze]

You should just return it to Audiophonics, this is clearly a defect and not a design issue. I mean they could have saved money on a power switch.

Internet photo of MPA-S250NC, does not look like that is anything to go wrong. Power button is just a control signal. It even has an earthed chassis. If you can get shocked at this point, I would check the house's earth connection.

Note that in many appliances, despite an earthed chassis, the secondary side can still be floating, and couple up to half mains AC voltage, so it may sting if you brushed against for example the RCA connectors. But it will not hurt as much if you hold the RCA connector, for example. Just like how static on a doorknob works. And this is acceptable by the industry as long as the current through your body is below a certain limit.

One possible reason for an appliance to remain powered up despite an off-ed power switch is wiring issue. This applies more to switches and broken wiring on the AC wires themselves. For example, a switch that only cuts Live but by wiring mistake it cuts the Neutral. Sometimes this allows a capacitive path from Live to Earth to power the appliance (common-mode EMI filter comes to mind). I think if I thought harder there can be more fault examples. But in this case this is unlikely since the power switch here is just a control signal and the SMPS looks like a 2-pin one. Maybe a fault condition allowed AC to leak somewhere, and since this device is earthed it will form a complete loop when you touch it.

tl;dr -
1) This is a fault, get Audiophonics to check the unit
2) Check your power cabling
3) The "shocking" may be normal or may be due to the fault condition, you just need to compare it against an LCD TV or an AVR. Generally if it does not make you go "WAT THE ****" and jolt your hand away feeling all cramp and numb it's normal.
3a) Or sometimes the fault condition allows that amount of "shocking" to sufficiently power the appliance.

 

[AnalogSteph]

I'll look for a hexagon shaped screwdriver, I think I own one.

Torx will generally do as well. (BTDT.) By the looks of it you need to loosen two of these and two Phillips on the back.

OP, this may be a problem just with the power switch or its wiring (can't hurt to check it against the stock photo) and not related to the other issues.

This unit is built as IEC Class I, which is to say mains protective earth connects to chassis. (That's the green-yellow wire.) If you have collected static electricity from walking around in a dry environment, you may find touching the case a somewhat "shocking" experience as the charge makes its way to earth potential. A PC would have done the same.

As for the hum, please test without input cables connected. I suspect you may have unwittingly used unsuited cabling to interface from unbalanced outputs and incurred a ground loop. (These cables should generally do the trick, only in severe cases the shield may need to be disconnected from XLR pin 1. Bit of a strange-looking XLR, not sure how these open but they generally do.)

Is the outlet you're using protected by an RCD/GFCI? From what I gather these are not quite as common in the US as they are here.

 

[archerious]

You should just return it to Audiophonics, this is clearly a defect and not a design issue. I mean they could have saved money on a power switch.

Internet photo of MPA-S250NC, does not look like that is anything to go wrong. Power button is just a control signal. It even has an earthed chassis. If you can get shocked at this point, I would check the house's earth connection.

Note that in many appliances, despite an earthed chassis, the secondary side can still be floating, and couple up to half mains AC voltage, so it may sting if you brushed against for example the RCA connectors. But it will not hurt as much if you hold the RCA connector, for example. Just like how static on a doorknob works. And this is acceptable by the industry as long as the current through your body is below a certain limit.

One possible reason for an appliance to remain powered up despite an off-ed power switch is wiring issue. This applies more to switches and broken wiring on the AC wires themselves. For example, a switch that only cuts Live but by wiring mistake it cuts the Neutral. Sometimes this allows a capacitive path from Live to Earth to power the appliance (common-mode EMI filter comes to mind). I think if I thought harder there can be more fault examples. But in this case this is unlikely since the power switch here is just a control signal and the SMPS looks like a 2-pin one. Maybe a fault condition allowed AC to leak somewhere, and since this device is earthed it will form a complete loop when you touch it.

tl;dr -
1) This is a fault, get Audiophonics to check the unit
2) Check your power cabling
3) The "shocking" may be normal or may be due to the fault condition, you just need to compare it against an LCD TV or an AVR. Generally if it does not make you go "WAT THE ****" and jolt your hand away feeling all cramp and numb it's normal.
3a) Or sometimes the fault condition allows that amount of "shocking" to sufficiently power the appliance.

I plan to return it for sure.

 

[March Audio]

As for the hum, please test without input cables connected. I suspect you may have unwittingly used unsuited cabling to interface from unbalanced outputs and incurred a ground loop. (These cables should generally do the trick, only in severe cases the shield may need to be disconnected from XLR pin 1. Bit of a strange-looking XLR, not sure how these open but they generally do.)

.

looks like just RCA, no XLR.

Its not wired as per Hypex advice.

 

[restorer-john]

Thought nothing of it, until I went to move it from my office to my listening room and it shocked me!

What shocked you exactly? Did you unplug the unit and exposed pins of the power cable gave you a little hit? That is common with certain rectified and filtered SMPS front ends. They need a short time to discharge.

I find it hard to believe a logic level switch could have shocked you, especially as it appears this unit is correctly earthed.

 

[AnalogSteph]

JFTR, I'm pretty sure we are talking about the mains power switch at the back, not the soft power. At least that's what I assumed.

looks like just RCA, no XLR.

Oh, I missed the RCA version.

Its not wired as per Hypex advice.

View attachment 81478

I couldn't tell from the pictures to be honest. Now that would be silly.

 

[March Audio]

Note that in many appliances, despite an earthed chassis, the secondary side can still be floating, and couple up to half mains AC voltage, so it may sting if you brushed against for example the RCA connectors. But it will not hurt as much if you hold the RCA connector, for example. Just like how static on a doorknob works. And this is acceptable by the industry as long as the current through your body is below a certain limit.

.

Not quite.

SMPS supplies do have leakage currents from the EMI reduction caps which connect live and nuetral to earth. (Y caps -https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/ )

So if your device is class ii (not earthed) then exposed metal can sometimes have a bit of a "live" feel or feel like they "vibrate" as you brush your hand across them. The maximum permissible leakage current is strictly limited ( 3.5mA IEC-60950-1 regulations ) and should not feel like a shock. Note this is normal, perfectly acceptable and safe.

If the product is class i (earthed) then you should not feel this.

In countries such as UK/AU the neutral is typically tied to earth at the consumer box/local transformer

However in the US my understanding is that the local transformers are centre tapped which is also tied to earth. If you have correct wiring in your house and the product is earthed then the chassis will not be floating at 1/2 supply, it should be at earth potential so no you wont feel a shock.

 

[restorer-john]

In countries such as UK/AU the neutral is typically tied to earth at the consumer box/local transformer

The neutrals are also tied at most supply poles to earth. I was speaking with Energex (our supply in Qld) engineers and told them I'd seen a bunch of swinging neutrals (thieves cut the last few metres with an axe). They said some days, all they do is replace the pieces chopped off, 30 or 40 of them. All for a few cents worth of copper at the scrappers...

My personal opinion is all metal cased gear, be it test instruments or HiFi should be earthed. Anything where a consumer can come into contact with metal casework has the potential for fatal shock. Be that from insulation/component failure to ingress of objects (bobby pins for example) Double insulation as a standard is a bit of a joke, especially when it isn't adhered to by all manufacturers. I often see exposed primary power transformer pins sitting a few mm below perforated grille top panels and power switches secured poorly with uninsulated terminals- all bearing the double insulated symbol.

I see @March Audio takes insulation seriously and that should be reassuring to owners of that gear.

 

[March Audio]

The neutrals are also tied at most supply poles to earth. I was speaking with Energex (our supply in Qld) engineers and told them I'd seen a bunch of swinging neutrals (thieves cut the last few metres with an axe). They said some days, all they do is replace the pieces chopped off, 30 or 40 of them. All for a few cents worth of copper at the scrappers...

My personal opinion is all metal cased gear, be it test instruments or HiFi should be earthed. Anything where a consumer can come into contact with metal casework has the potential for fatal shock. Be that from insulation/component failure to ingress of objects (bobby pins for example) Double insulation as a standard is a bit of a joke, especially when it isn't adhered to by all manufacturers. I often see exposed primary power transformer pins sitting a few mm below perforated grille top panels and power switches secured poorly with uninsulated terminals- all bearing the double insulated symbol.

I see @March Audio takes insulation seriously and that should be reassuring to owners of that gear.

Class ii is perfectly safe, its enshrined in regulations and its everywhere. Things like TVs may have a plastic case but still have metal antenna and input connectors. We dont see daily reports of people being electrocuted by class ii gear. Clearly you cant account for manufacturers that dont follow the rules, but that is true of anything. If the internal clearance is 6mm (IIRC) its not an issue. All mains cables just rely on double insulation, they can easily get mechanically damaged. Thats much more likely a scenario than anything happening inside a product.

Any product with a vent hole could have very small foreign objects pushed into it. Earthing wont save you from a short circuit created by that circumstance and a resulting fire for example.

 

[restorer-john]

Class ii is perfectly safe, its enshrined in regulations and its everywhere. Clearly you cant account for manufacturers that dont follow the rules, but that is true of anything. If clearance is 6mm (IIRC) its not an issue. All mains cables just rely on double insulation, they can easily get mechanically damaged.

Any product with a vent hole could have very small foreign objects pushed into it. Earthing wont save you from a short circuit created by that circumstance and a resulting fire for example.

Let's not have an argument today about earthing. I gave you a compliment on your efforts with insulation.

But, you're missing the point about double insulation with metal encased devices. It's not perfectly safe and never has been. Every single kitchen appliance sold in this country with any exposed metal at all, must be earthed. I gave you an example where a metal object (bobby pin, tack, even a staple) can make a double insulated case live. I've seen it happen. A correctly earthed cabinet with the same scenario will instantly blow the product fuse and then the breaker on the distribution panel. And that is in the absence of an ELCB/RCD. With an ELCB/RCD it will likely trip before the main fuse and breaker panel. In short (pun intended) earthing metal cased mains powered objects is inherently safer than not.

A double insulated product in a live casework scenario will trip absolutely nothing until a person comes in contact with the case and then they have to hope to goodness the ELCB trips. The ELCB sees no differential between active and neutral return currents until that person touches the case and provides a path to earth.

Anyway, I have heaps of double insulated HiFI gear, just as you likely have. It is safe enough I guess, but I don't for one second trust anything I haven't inspected thoroughly and the disasters I have seen would make your toes curl.

 

[March Audio]

Let's not have an argument today about earthing. I gave you a compliment on your efforts with insulation.

But, you're missing the point about double insulation with metal encased devices. It's not perfectly safe and never has been. Every single kitchen appliance sold in this country with any exposed metal at all, must be earthed. I gave you an example where a metal object (bobby pin, tack, even a staple) can make a double insulated case live. I've seen it happen. A correctly earthed cabinet with the same scenario will instantly blow the product fuse and then the breaker on the distribution panel. And that is in the absence of an ELCB/RCD. With an ELCB/RCD it will likely trip before the main fuse and breaker panel. In short (pun intended) earthing metal cased mains powered objects is inherently safer than not.

A double insulated product in a live casework scenario will trip absolutely nothing until a person comes in contact with the case and then they have to hope to goodness the ELCB trips. The ELCB sees no differential between active and neutral return currents until that person touches the case and provides a path to earth.

Anyway, I have heaps of double insulated HiFI gear, just as you likely have. It is safe enough I guess, but I don't for one second trust anything I haven't inspected thoroughly and the disasters I have seen would make your toes curl.

Sorry John but its impossible not to have an argument when you are simply misinformed about the subject.

You are simply incorrect about metal cased products requiring to be earthed.

Im saying this as Im am looking at my class ii non earthed Yamaha metal cased AV amp, Panasonic bluray player, BW sub etc, etc etc. There are literally hundreds of thousands, probably millions of these sorts of products in use globally and no evidence of any safety issue.