Getting electric shocks from Logitech G29 + wheelstand

[Cantatablau]

Seriously, if you value life, at least borrow a Voltmeter
and sort out the issues instead of guessing and hoping
that, because you are still alive, there is no danger.

Yeah, I think this is good advice. It was necessary to ask here first, though, because my only knowledge of electricity is what I remember of my high school physics classes 15 years ago. Without asking and hypothesising, I would have just been a clueless person in possession of a voltmeter. They're pretty cheap on Amazon, so I'll get one and report back here with the results.

 

[blekenbleu]

so I'll get one

Get one with an Ohmmeter and hopefully beeper for continuity.
Be extremely methodical with measurements.
Make a list of equipment and write down readings;
don't depend on remembering.

capacitors whose role is to reduce emissions

One problem is that too many capacitors fail over time.
This has become more common over the last 30 years, where
EMI circuits which may have been designed for capacitors
to more or less balance or cancel will become unbalanced.
ESR meters have become nearly as essential as Ohmmeters...

Begin by disconnecting all wires to the GT Omega wheel stand,
then measure continuity between each metal piece of the stand.
Expect to discover that some pieces mechanically connected are
not electrically connected.
This is very common with aluminum, but not unusual with steel.
At your wall outlet, measure voltage (be sure to switch away from Ohms)
between the ground pin and each AC prong. For U.S. wall outlets,
with ground pin at the bottom, right slot should be 110-120VAC and left slot
should be 0 VAC, since ground and neutral are tied together at circuit breaker boxes. It is not unusual for some voltage to show up between neutral and ground, thanks to corrosion and so-called cold flow, where resistance increases over time with heat cycles at wire connections.
A knowledgeable electrician should correct any house wiring issues.
I nearly always find loose screws in older house load centers.
Many wall outlets are daisy-chained,
and it takes only one poor connection at any to ruin your day.

Plug each piece of 110VAC equipment in separately, and measure voltage
between any exposed metal (e.g. USB outer socket) and wall outlet ground
one each piece before plugging in the next piece. For USB sockets,
it is easier to plug in a cable and measure metal on plug at the other end, after having first verified continuity between metal on both plugs.

Only plug things together after each piece is individually checked.
Measure voltages between exposed metals for each piece of equipment
before connecting any.

Connect equipment, one at a time, to the wheel stand
and measure wheel stand voltage relative to wall outlet ground.

There is no magic, but there are intermittents!

 

[Neilski]

One problem is that too many capacitors fail over time.
This has become more common over the last 30 years, where
EMI circuits which may have been designed for capacitors
to more or less balance or cancel will become unbalanced.
ESR meters have become nearly as essential as Ohmmeters...

Capacitors can indeed fail, and if those particular capacitors fail in a bad way (i.e. short circuit) they could make the whole appliance deadly to touch. However, I've read that those caps are specifically designed to make that exceptionally unlikely.
My understanding of the leakage issue though is that supplies designed with this kind of EMI mitigation will arrive brand-new from the factory with the leakage doing exactly what it's doing on my Logitech PSU, before any age-related issues get a chance to kick in.

At your wall outlet, measure voltage (be sure to switch away from Ohms)
between the ground pin and each AC prong.

I agree with almost all of your suggestions about buying a multimeter and using it to test what's going on, but please don't propose to someone who is not confident with electricity that they stick a multimeter into a mains outlet. That could end very badly in a whole variety of ways.

 

[blekenbleu]

That could end very badly in a whole variety of ways.

If they have appreciable voltage on neutral, that could end badly.
Bad news rarely improves with age.

 

[trichens]

If you can get hold of a meter to measure resistance between the exposed fixings you are touching when you get a shock, and the USB cable shield that you plug into the PC - you don't have to actually plug it into the PC - you should be able to find out if you have a complete circuit.

That would be the same whether it's plugged into the PC or the console.

 

[blekenbleu]

measure resistance

Won't address inductive/capacitive coupling issues.
Also, trying to measure resistance
when stuff is connected can blow an Ohmmeter
if connection is open
and/or there is appreciable Voltage difference.

 

[Neilski]

If they have appreciable voltage on neutral, that could end badly.

Agreed, but looking at the report in the OP: lots of people get a slight buzz from things powered by unearthed power bricks, so that's not by itself a scary observation. I would suggest that faults with household wiring are rather less common, and that anyone who suspects they may be affected should consult a professional in the first instance unless they are competent to do the checks themselves.
There are plenty of horror stories about cheap and cheerful multimeters that claim to be safe with voltages well in excess of mains supplies, but turn out to be very unsafe indeed. Even a high-quality multimeter can assist you to harm yourself, if you for example plug the leads into the wrong sockets when working with mains voltages.

 

[Cantatablau]

So the multimeter arrived today, and the results have been very weird, and inexplicable to me.

Here's a picture of the multimeter.

I've been getting readings of mere millivolts from the bolts in the wheel stand. Nothing else is giving me a reading at all, not the metal platform the wheel is mounted on, not the metal frame of the wheel stand, not the aluminium chassis of the iMac, nothing. The bolts give me between 1 and 10 millivolts (it fluctuates). The weird thing is, it doesn't seem to make any difference if the wheel is plugged in at the wall outlet, if it is connected to the computer or PlayStation via USB, or if it is unplugged from everything; the reading stays the same. The other weird thing is I only seem to get readings when one testing probe is being used, not when both are.

I tried reading between the iMac and the bolts, between the bolts and the metal base of the chair, between the bolts and my body; same tiny readings of 1-10 millivolts. I did't get a reading at all when testing for current or AC voltage. The highest reading I was able to get was just from holding both testing probes between my fingers: around 70 millivolts.

What conclusions can I draw from this? Would it be a faulty multimeter? Should I do other tests?

 

[Neilski]

What conclusions can I draw from this? Would it be a faulty multimeter? Should I do other tests?

Two things to ask:
Have you tested the meter on a known voltage, e.g. a 1.5 V battery (on the DC range)?
When you're using both probes and touching the bolt with one, where are you putting the second one?

 

[Cantatablau]

Two things to ask:
Have you tested the meter on a known voltage, e.g. a 1.5 V battery (on the DC range)?

I just tested it on a 1.5V-rated AAA Energizer Max and it gave a reading of 1.59.

When you're using both probes and touching the bolt with one, where are you putting the second one?

I've tried touching the wheel stand chassis in different parts, as well as the base of the chair, the iMac chassis, or just holding it in the air, and it always gives me a similar reading.

 

[blekenbleu]

I tend to ignore values less than 0.1V when testing power grounding.

Millivolts are everywhere, some (DC) by thermocouple action
from simply different metals in contact at different temperatures.

If you have ever provoked hum in an audio amplifier,
that results from AC millivolts inductively and/or capacitively coupled
from fields generated e.g. by AC power wiring in buildings.

As @Neilski pointed out, serious faults in AC wiring should be uncommon
(although I encountered some in each of 3 most recent homes),
but having, as a first step, reduced their likelihood as a source
of your issues allows moving on.

When readings larger than those "noise" milliVolt levels are registered,
then potentially problematic situations are in play.

Keep in mind that, under worst case conditions,
skin resistance is drastically reduced e.g. by salty perspiration,
electricity of 1.5V can be sensed and 24V can be deadly.

 

[Cantatablau]

Ok, last night I got much more methodical with my testing and I found some answers.

TL;DR: the problem is the iMac, but if I unscrew the pedal base from the wheel stand, it goes away.

Multimeter tests

Under the guidance of an engineer friend, I did a ton of tests, with the following results:

Testing for AC voltage between a bolt on the wheel stand and the earth plug of a wall outlet: 0-0.2V.

Testing for AC voltage between a bolt on the wheel stand and one of the iMac's USB ports: 0

Testing for AC voltage between a bolt on the wheel stand and the floor: 0

Holding the black probe tightly between my fingers while touching the red probe to a bolt on the wheel stand and standing barefoot on the floor: 0.5V AC, 1.5V DC.

Electric shock tests

With the wheel plugged into the wall and the iMac, and with me standing barefoot on the floor, touching the wheel mounting platform with my thumb: no shock.

As above, but touching with my forearm: shock.

As above, but wearing flip-flops: no shock.

As above, having removed the screws holding the wheel to the stand (without flip-flops): shock.

As above, with a piece of cardboard between the wheel and the mounting platform: shock.

As above, without cable management (cable ties holding cables against the frame of the wheel stand removed): shock.

As above, but with the pedal base unscrewed from the mount: no shock.

As above, but with the pedals reattached using shorter screws: shock.

As above, but with the USB cable disconnected from the iMac: no shock.

As above, but with the wheel connected to the PS3 instead of the iMac: no shock.

As above, but with the wheel connected to a laptop: no shock.

So, through process of elimination, we were able to ascertain that the problem is the iMac, but we're not exactly sure why. I know iMacs have weird exposed power supplies, so I wonder if this could be the cause. By unscrewing the pedals from the wheel stand, the problem goes away. So the solutions to the problem seem to be 3:

1. Play with shoes (difficult due to the large size of my feet).
2. Use nylon screws (may be a problem due to their limited mechanical strength).
3. Create an earth for one of the screws on the pedal base (annoying because I'm constantly moving the wheel stand from the living room to the computer room).

Obviously the long-term solution would be to build my own PC, but I'm getting married next year, so currently all my disposable income is going towards that. For now, my only option for playing games more realistic than GT6 is bootcamping my GF's iMac.

 

[trichens]

I'm not saying you should do anything to your Logitech gear but...
This image shows the wiring on the clutch pedal - they are all wired the same.

The green circle is one of the threaded fixings.

The red circle shows the wire that goes from the potentiometer to the metal bracket. This links the bracket electrically to the rest of the wiring.

If you are getting shocks through the pedal fixings then it would have to be coming from this earth/ground wiring.

Perhaps you could try insulating washers under the bolt heads? And some insulating tape around the few millimetres of thread that doesn't screw into the fixings?
You just need to eliminate metal to metal contact.

 

[Cantatablau]

I'm not saying you should do anything to your Logitech gear but...
This image shows the wiring on the clutch pedal - they are all wired the same.

View attachment 600511

The green circle is one of the threaded fixings.

View attachment 600512

The red circle shows the wire that goes from the potentiometer to the metal bracket. This links the bracket electrically to the rest of the wiring.

View attachment 600513

If you are getting shocks through the pedal fixings then it would have to be coming from this earth/ground wiring.

I'm afraid I don't know how to interpret this information.

 

[trichens]

or do a search for M6 nylon shoulder insulating washers...

The previous post was just to show how the wheel stand is getting linked to the wiring...

 

[blekenbleu]

Holding the black probe tightly between my fingers while touching the red probe to a bolt on the wheel stand and standing barefoot on the floor: 0.5V AC, 1.5V DC.

Is there any possibility that pedals did not come originally with the G29?
Having only owned G29 pedals but seen contradictory schematics,
it may be that pedal grounding was switched,
somewhere along the G25/27/29 line.

If so, then what is supposed to be +5V (or +3.5V) from the wheel
ends up getting connected to pedal metal.
This reportedly showed up with some adapters
for attaching Logitech pedals directly by USB.
Pedal axes report backward in Windows joy.cpl
Game Controller control panel,
which can be inverted in some software,
but some adapters instead swapped +5 and ground connections,
provoking weird intermittent failures,
depending on whether/when pedal metal is actually grounded.

 

[Neilski]

TL;DR: the problem is the iMac, but if I unscrew the pedal base from the wheel stand, it goes away.

Delighted that you've now found the definitive cause!

Multimeter tests

Very puzzled by these though...

Testing for AC voltage between a bolt on the wheel stand and the earth plug of a wall outlet: 0-0.2V.

...this one should very definitely have registered a decent voltage (maybe 60 V AC or thereabouts). Oh well, can just be filed under irrelevant mysteries I guess

Anyway, I get that earthing the stand is not something you're super enthusiastic about, given your usage.
However, you can still go the earthed PSU route for the Logitech wheel (with the caveat that it has to earth the 0 V line), even though the problem comes from the iMac... The wheel stand will still become earthed, regardless of where the earth is connected from, and that will end the shocks

 

[trichens]

I use a Leo Bodnar cable so my pedals aren't connected through the Logitech wheelbase and my rig is made of mainly scrap wood so no eathing issues - a variation of the good old Deathmobile!

 

[Neilski]

I use a Leo Bodnar cable so my pedals aren't connected through the Logitech wheelbase

Me too, for the last several months!

 

[Cantatablau]

So a little update: as a quick and dirty fix, I tried swapping the metal washers for rubber ones, obviously at the expense of a little mechanical strength. Here's a pic. I also played with shoes on, just to be extra safe. The whole time I was playing, I was getting annoying little zaps from my shift paddles as well as my mouse. Not the continuous, kind of burny-feeling shocks from before, just the type of little quick ones you get from statically-charged clothing or carpet.