high potential on chassis CD-player

[jitter]

Recently I had a discussion in the Chip Amp section with some of you about whether or not to connect safety earth or protective earth (I'll call it PE from now on) to the chassis of DIY equipment (Odd grounding problem). This had me going over all the wiring of my audio and video equipment. At a certain point I was reconnecting the SPDIF coax from my unearthed (appliance class II) CD-player to my earthed (aplliance class I) DAC. Because I had to reach behind the two I happened to grab the outside of the RCA connector attached to the CD-player while I touched the DAC's chassis with my wrist. That felt like being bitten or something.

I measured the AC voltage with a DMM (10 M input impedance) between the chassis of both devices.
There was a 200 Vac differential between them with the CDP switched off that dropped to about 100 Vac when switched on.
I reversed the mains plug of the CDP and got less then 2 Vac when switched off, but still about 100 Vac when switched on.

Now this CDP has been giving me a lot of aggro over the years which I thought to have solved a while ago (Very strange fault (CD-player)). Not so long ago it began to misbehave again, so I gave up and connected the SPDIF to the DAC (it's the analogue stage that keeps going wrong).

But after being bitten, I inspected the innards of the CDP again, but now focusing on the filter behind the mains entrance. Despite having a 3-prong IEC socket, the PE has deliberately not been connected by the manufacturer, thus selling it as a class II device. The design of the mains filter, though, looks like it had originally been designed for a class I device. Perhaps in a more expensive guise, this CDP would have had balanced connections. Usually PE is connected to the chassis when balanced in- and outputs are used.

Closer inspection after removal of the filter pcb confirmed my suspicion that C2 and C3 are across L and PE and N and PE (or rather would-be-PE). As you can also see in the picture the PE pin has been cut before insertion in the pcb.
Under the screw, marked G1, is a copper threaded standoff fixed to the chassis. It touches a pad that would have connected to PE of the mains entrance. I'm assuming the high potential between my DAC and the CDP is caused by C2 and C3 as long as it's connected to mains but not yet to the DAC.
While unscrewing G1 I noticed it wasn't very tight, so the connection to the chassis might not have been very good, perhaps intermittent. Recently I noticed the display of the CDP scrambling whenever I switched the DAC on or off. Might this have something to do with the not-so-good connection of the filter pcb to the chassis?

Isn't it a bit strange that a mains filter clearly designed to be used with PE can find its way into a class II appliance?
Wouldn't that mean high leakage current trough the interlink shields to the DAC?

But my main question is: can I (or rather, am I allowed to) connect PE to the chassis changing it into a class I device?

[richie00boy]

Absolutely shocking (ha!). Is the double insulated (square within square) logo on the equipment? Are you sure the manufacturer cut the connection or did you buy it used or ex demo?

I would immediately remake the protective earth connection.

[jitter]

Originally Posted by richie00boy

Absolutely shocking (ha!). Is the double insulated (square within square) logo on the equipment? Are you sure the manufacturer cut the connection or did you buy it used or ex demo?

I would immediately remake the protective earth connection.

No, the only logo to be found on the back is the CE marking.
EDIT: the manual isn't much help either. The manual of the MkII, however, DOES instruct to disconnect mains before connecting or disconnecting any of the (other) cables. Guess why...

I bought it new in 1998 or 1999, so I can't really remember if I got a sealed box or one that was already open. I'm pretty sure it wasn't the demo as that one had ventilation slits, mine doesn't.

If the PE connection was cut afterwards, chances are the bit stuck in the pcb would have been left in there. The unused holes in the pcb are all empty and there are no signs of desoldering. Both give me reason to believe the CDP left the factory this way.

Trying to find some pictures of the Primare D20, I found some of a slightly different (older?) version on the website of a modder (galleria foto 7). This one clearly shows a very similar mains filter with a 2-prong IEC socket. Another sign it was meant to be this way.

[richie00boy]

If it left the factory in that condition then I think health and safety people would be very interested in taking Primare to court for massive violation of electrical safety regulations.

[wwenze]

The current isn't enough to kill you (not enough to trip the circuit breaker either), but it sure will hurt like mad and mess with other earthed electronics connected to it.

Also, by not connecting the earth that pair of capacitors won't be able to do their job of filtering common-mode noise. Might as well remove it altogether to spare the agony.

[jitter]

I'm beginning to think that there's a big difference between regulations theory and practice.

If I'm not mistaken, regulations stipulate, at least in Europe, that class 2 or the double-square symbol be on the device. Yet on this CDP it's nowhere to be found. The CE marking is on it, suggesting it passed the safety tests required to be allowed to sell it in the EU.
Looking at some other CD-players on the modifiers website I linked to in my previous post, I can see several with a three-prong IEC socket bearing the double insulation logo. Obviously they don't have the PE pin connected to chassis. Apparently regulations don't forbid this.

Also, in class 1 devices, the PE must be connected to a post as close to the mains entrance as possible. This post must not be accessible from outside the device, i.e. one shouldn't be able to loosen it by e.g. unscrewing it. Yet some of our customers simply employ a faston connected to a central earth point on the back panel of the device to connect the PE pin of the mains entrance. This earth point can be loosened from the outside as the screw-heads are accessible. Still, it's sold all over the world, assuming that local authorities found it to comply with regulations...

Also, this device is a mix of RoHS and non-RoHS compliant pcbs. Outside of the EU, that's no big deal, but they're also sold inside the EU and I presume they're not part of RoHS exempt devices (transportation, medical and military).

Either regulations aren't that strictly applied by both the manufacturers and the regulatory authorities, or they aren't as stringent as we assume they are.

[jitter]

Originally Posted by wwenze

The current isn't enough to kill you (not enough to trip the circuit breaker either), but it sure will hurt like mad and mess with other earthed electronics connected to it.

Agreed, otherwise it wouldn't have passed the CE tests.

Also, by not connecting the earth that pair of capacitors won't be able to do their job of filtering common-mode noise. Might as well remove it altogether to spare the agony.

Agreed, as long as there are only class 2 devices in the audio system. Since I have a class 1 DAC, they will be connected to PE through the interlink shields. I don't like that idea because it seems to me that it will pollute signal-GND. Since connecting this CDP to PE amounts to nothing more that soldering in a bit of conductor, I will experiment with it and see if that has any effect on the noise.

[jitter]

I just turned the D20 into a class 1 device by connecting PE. Instead of soldering a bit of wire between the pcb and the PE pin, I chose to do it as in the picture instead. This way I could experiment quickly and easily and it can be brought back into original state without soldering.

Whether or not PE is connected on the D20 seemed to have no effect on the noise-floor (I just turned up the volume on the amp all the way). According to this excellent article (Audio Component Grounding and Interconnection), "Loops aren’t bad – it depends on what is on the loop.", holds true.

I do have a groundloop, though, if I connect the CD-player to both the amp and the DAC. Then, at higher volume a buz/hum is heard, I presume this is a ground loop (CDP<>DAC<>AMP<>CDP). Connecting PE doesn't affect it.

I see on the pcb there's the possibility to connect SPDIF through an output transformer, that would prevent a ground loop. For now, I will either only connect analogue or SPDIF. The analogue output of the CDP is better than that of the DAC, so I prefer that, but if it goes bad again...

[richie00boy]

What they have done is just incompetent and dangerous design. If no protective earth is present, the appliance MUST be double insulated. And having caps from a live side to case, without a protective earth, well it beggars belief. Are C2 and C3 Y rated?

[Juergen Knoop]

using Y caps from L&N to circuit/chassis ground is common practice in classII devices with switching supplies. This is not a safety risk and inside the standard, if the leakage current does not excede something like 0,5mA.
Sometimes multivoltage supplies designed for the 115V world have higher than allowed leakage currents when used at 230V. Those fail European standards.
regards