Hope y’all can help troubleshoot this issue in my trusty old Chord power amp. The SPM 900 was their first commercial production model.
Been using this amp almost daily generally without issue but recently noticed I was getting some power leakage to the chassis?
I feel this as a little tickle -an almost pleasant little buzz on your finger when you touch the amp but it is especially pronounced for example when you touch an input jack connected to my iPod.
Between the source and the Chord I am using a Akustyk passive preamp (basically a Khozmo stepped attenuator and input selector in a box).
Could be anywhere right?
Any likely candidates?
Where to start?
Thanks for looking
Been using this amp almost daily generally without issue but recently noticed I was getting some power leakage to the chassis?
I feel this as a little tickle -an almost pleasant little buzz on your finger when you touch the amp but it is especially pronounced for example when you touch an input jack connected to my iPod.
Between the source and the Chord I am using a Akustyk passive preamp (basically a Khozmo stepped attenuator and input selector in a box).
Could be anywhere right?
Any likely candidates?
Where to start?
Thanks for looking
Two possibilities.
1) Leakage of transformer or capacitors in high voltage circuits, high humidity. Ground fault.
2) Static electricity from synthetic clothing or plastic shoe soles. Feels like a tingling sensation when touching grounded metal objects. Antistatic treatment, grounding strap.
1) Leakage of transformer or capacitors in high voltage circuits, high humidity. Ground fault.
2) Static electricity from synthetic clothing or plastic shoe soles. Feels like a tingling sensation when touching grounded metal objects. Antistatic treatment, grounding strap.
Disconnect everything except the speakers.
Notice if the tingle is still there.
If not, something external is feeding the leakage into the amp. - simple to determine.
If yes, then there's a serious problem with the amp.
Notice if the tingle is still there.
If not, something external is feeding the leakage into the amp. - simple to determine.
If yes, then there's a serious problem with the amp.
I've experienced (and still do with some of my stuff) this phenomenon... 99.9% this is normal behaviour in your case. I get this 'feeling' with my laptop on mains (sometimes), cooker tops, Sony and Micromega CD players...
There is no safety risk or excess leakage in all these cases.
This very same question has cropped up on here in the past.
There is no safety risk or excess leakage in all these cases.
This very same question has cropped up on here in the past.
Personally, I don't want to feel any "tingle" whenever I handle my equipment. (please, no dirty jokes).
A poor grounding is sometimes the fault.
Other times, those various capacitors and resistors tied to the chassis from the mains is the reason.
A safe test:
Take a digital meter like a Fluke, and set it for AC volts.
Grasp one probe tip, and with the other, touch the chassis, knobs, cover screws, etc.
It "should" only read a few volts leakage (4v, maybe a few more?) if proper grounding is intact.
This test can be used for any home appliance like a washing machine, etc.
Anything substantially more, like 40-60 volts AC means there's an issue - and needs correcting.
A poor grounding is sometimes the fault.
Other times, those various capacitors and resistors tied to the chassis from the mains is the reason.
A safe test:
Take a digital meter like a Fluke, and set it for AC volts.
Grasp one probe tip, and with the other, touch the chassis, knobs, cover screws, etc.
It "should" only read a few volts leakage (4v, maybe a few more?) if proper grounding is intact.
This test can be used for any home appliance like a washing machine, etc.
Anything substantially more, like 40-60 volts AC means there's an issue - and needs correcting.
please enlighten me as to how this tests for leakage to ground? and would you do this with bare feet too...?
Thanks for all your help. I see some venerable names on my thread and I am humbled as always by the generosity of the DIYA community.
THE FIX
By a PM @rayma suggested a turn the power plug around in the wall socket. Bingo, no tickle.
Obviously I was keen to try the simple fixes first before I went poking around inside this amp - it is well packed in there with little room for much except dust particles.
I feel much safer and happier that small voltage isn't leaking back into any source.
@mooly I also feel similar with my laptop especially if only light touch.
THE FIX
By a PM @rayma suggested a turn the power plug around in the wall socket. Bingo, no tickle.
Obviously I was keen to try the simple fixes first before I went poking around inside this amp - it is well packed in there with little room for much except dust particles.
I feel much safer and happier that small voltage isn't leaking back into any source.
@mooly I also feel similar with my laptop especially if only light touch.
Chord products are indeed SMPS and this is the first power amplifier model, AFAIK.
Discover what makes Chord amplification unique - Chord Electronics Ltd
Discover what makes Chord amplification unique - Chord Electronics Ltd
If the power plug is reversible in the wall outlet, then use yes, reverse it to see if the feeling disappears.
The simplest question of all: is the amplifier connected to a wall socket with PE (connected)?
It should be! If you connected the device to a 2 pin wall socket you instantly know that is it not connected right ↯ ☠
This is an often occurring issue when equipment with PE IEC inlet is connected to a non PE wall socket. The filter caps in the SMPS then form a voltage divider for mains voltage when PE is not connected thus leaving a leakage voltage on the chassis. Imagine 2 small capacitors in series (one connected to L and the other to N) and the middle point should be connected to PE but isn't. This point is also connected to the metal chassis/casing.
I can not count the times that I have found this in audiophile homes 😀 Many Euros are spent on audio but no PE in the living room.... Or PE available but faulty extension cables/boxes i.e. non PE Schuko sockets with PE Schuko plugs in them thereby interrupting the PE connection. Please notice that the filter for the SMPS will not work OK and safety in is question too.
It is also simple to measure. Just measure AC from chassis/casing to a known PE point. If around 0V then it is OK. You could also measure Ohms but only so if you know what to do. My guess is that you will measure 90 ...115V.
Safety/PE may be an issue in Vientiane/Laos but I strongly suggest to correct the situation if my guess is right also for kitchen equipment, washing machine etc. as PE may save a life when any of the devices breaks down.
It should be! If you connected the device to a 2 pin wall socket you instantly know that is it not connected right ↯ ☠
This is an often occurring issue when equipment with PE IEC inlet is connected to a non PE wall socket. The filter caps in the SMPS then form a voltage divider for mains voltage when PE is not connected thus leaving a leakage voltage on the chassis. Imagine 2 small capacitors in series (one connected to L and the other to N) and the middle point should be connected to PE but isn't. This point is also connected to the metal chassis/casing.
I can not count the times that I have found this in audiophile homes 😀 Many Euros are spent on audio but no PE in the living room.... Or PE available but faulty extension cables/boxes i.e. non PE Schuko sockets with PE Schuko plugs in them thereby interrupting the PE connection. Please notice that the filter for the SMPS will not work OK and safety in is question too.
It is also simple to measure. Just measure AC from chassis/casing to a known PE point. If around 0V then it is OK. You could also measure Ohms but only so if you know what to do. My guess is that you will measure 90 ...115V.
Safety/PE may be an issue in Vientiane/Laos but I strongly suggest to correct the situation if my guess is right also for kitchen equipment, washing machine etc. as PE may save a life when any of the devices breaks down.
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This is simply an assumption that can be quite dangerous!!! Please check my explanation in previous post. I have seen too many PE mistakes/errors to do any assumptions. ALWAYS measure voltage on metal chassis when one gets the tickling feeling. When experienced also measure Ohms in switched off state from the metal casing to a known good PE point. If the casing/chassis is floating (and thus has a leakage voltage on it) you just know things are wrong. Then there IS a safety risk. A device that is connected to PE can not give any tickling feeling at all as voltage on the casing would be 0 🙂
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I stand by what I posted Jean. This phenomenon of a 'buzzy' feeling in your fingertip as you move it across a surface is very common and does not indicate any safety issue of leakage.
(leakage tests should always be checked by measurement of leakage current rather than voltage. Manufacturers sometimes give figures for a raw leakage test, typically 0.5 milliamps as a maximum. Sometimes the test is to measure volt drop across an R/C network of for example a 1k5 and 0.15uF cap. 0.75v would be the limit here.)
(leakage tests should always be checked by measurement of leakage current rather than voltage. Manufacturers sometimes give figures for a raw leakage test, typically 0.5 milliamps as a maximum. Sometimes the test is to measure volt drop across an R/C network of for example a 1k5 and 0.15uF cap. 0.75v would be the limit here.)
Well that is fine (and truely unsafe as we learn to check and not to assume) but I would rather have the OP check the chassis to have any voltage on it as the official method you describe is too difficult for laymen. It is the method for manufacturers but the OP is no manufacturer but a consumer.
Certainly in countries where PE and non-PE plugs and wall sockets can unfortunately be used mixed (by design) or where electrical safety is of no concern this phenomenon is common. Solved this riddle many many times in various countries.
Certainly in countries where PE and non-PE plugs and wall sockets can unfortunately be used mixed (by design) or where electrical safety is of no concern this phenomenon is common. Solved this riddle many many times in various countries.
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Un-earthed SMPS are very disconcerting due to the leakage current (which is due to capacitors specifically added to reduce the switching-frequency leakage which would be much worse, and really dangerous).
The high frequency transformers used in SMPS leak considerable current through inter-winding capacitance because the frequency is much higher than mains. Adding a capacitor between the primary and secondary ground shorts this out, but with a two-prong power cord that cap maybe between live and output, injecting the lower frequency mains instead.
I'd always earth the output side of a SMPS if possible - did this for my laptop supply so it didn't tickle my wrists (VERY irritating).
To my mind such a supply is not double-insulated and therefore must be earthed.
The high frequency transformers used in SMPS leak considerable current through inter-winding capacitance because the frequency is much higher than mains. Adding a capacitor between the primary and secondary ground shorts this out, but with a two-prong power cord that cap maybe between live and output, injecting the lower frequency mains instead.
I'd always earth the output side of a SMPS if possible - did this for my laptop supply so it didn't tickle my wrists (VERY irritating).
To my mind such a supply is not double-insulated and therefore must be earthed.
Indeed you are correct Jean-Paul
Our sockets here are type B but also allow type c plugs so I have a Schuko plug going into the 2 pins of the B socket- thus no PE connection
I have long wondered about this and should know better as my father is an electrician and I have learnt a lot from him. I plan to remedy this through the week By changing the plug termination on my audio Equipment and elsewhere in the home where this is the case.
Thanks for your help and of course concern for my and my families continued existence🙂
Our sockets here are type B but also allow type c plugs so I have a Schuko plug going into the 2 pins of the B socket- thus no PE connection
I have long wondered about this and should know better as my father is an electrician and I have learnt a lot from him. I plan to remedy this through the week By changing the plug termination on my audio Equipment and elsewhere in the home where this is the case.
Thanks for your help and of course concern for my and my families continued existence🙂
Banzai! Thanks for the feedback. It is always nice to hear back results when advice is given. It is this feedback that lowers the failure rate of advices 🙂
Please make sure your remedy is to use PE wall sockets AND to connect PE with the standard 2.5 mm2 green/yellow solid copper wire. Also check if your PE is connected (at all) at the entry point according the regulations as one sees a thing here and there. Also make sure to check and measure the results of your actions.
The reward for the work will be better sound quality, less mains polution, less garbage coming in from the grid, no more tickling feelings when operating equipment and best of all: safety
Bonus: mains filters also work ok after the actions.
Please make sure your remedy is to use PE wall sockets AND to connect PE with the standard 2.5 mm2 green/yellow solid copper wire. Also check if your PE is connected (at all) at the entry point according the regulations as one sees a thing here and there. Also make sure to check and measure the results of your actions.
The reward for the work will be better sound quality, less mains polution, less garbage coming in from the grid, no more tickling feelings when operating equipment and best of all: safety
Bonus: mains filters also work ok after the actions.
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For those interested in current leakage and measuring it, there are a number of good articles on the web about the subject. Most are written by the manufacturers of measurement equipment like Fluke. Seek and thee shall find. 🙂
Here's a nice one by Chroma Systems. It's good to read several sources for best coverage.
Leakage Current Test | Chroma
Here's a nice one by Chroma Systems. It's good to read several sources for best coverage.
Leakage Current Test | Chroma
As can be seen in various threads PE and correct grounding (let alone measuring leakage current) is too much for an average consumer/DIYer.
Let's keep it simple(r): if a device has a 3 prong plug (so with PE) then put the plug only in 3 prong wall sockets with PE.
Shorter: if a device has IEC with PE then use a PE socket!
Attached pictures of a Schüko plug and older wall socket that should never be used together. The older type wall socket without PE should be banned IMHO as it accepts Schüko plugs with PE thereby interrupting PE connection. For some reason people spend thousands of Euros on audio but many don't care to maintain and/or update their electrical installation. What is the use of expensive electronics that need PE when your electrical installation lacks PE?
Let's keep it simple(r): if a device has a 3 prong plug (so with PE) then put the plug only in 3 prong wall sockets with PE.
Shorter: if a device has IEC with PE then use a PE socket!
Attached pictures of a Schüko plug and older wall socket that should never be used together. The older type wall socket without PE should be banned IMHO as it accepts Schüko plugs with PE thereby interrupting PE connection. For some reason people spend thousands of Euros on audio but many don't care to maintain and/or update their electrical installation. What is the use of expensive electronics that need PE when your electrical installation lacks PE?
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