From Newsgroup: rec.games.pinball

I added a SPST toggle switch to my Gottlieb World Fair. I wired to basically take place of the bounce switch. Everything works fine, but when the switch is off I still read 5 or 6 volts across the hold relay. I’ve tried 3 different brand switches. This are all good quality switches rated at 10 to 15 amps. Is this just some false ghost voltage due to high multi meter impedance or do I have a problem? I’ve even ordered an analog meter to see if it makes a difference. I replaced the 2 cord plug with a 3 prong, but even with disconnecting the ground lug from the transformer I still get this stray voltage. Outlet tests ok.
Thanks
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From Newsgroup: rec.games.pinball

On 5/21/20 10:50 AM, Bob Monzo wrote:

I added a SPST toggle switch to my Gottlieb World Fair. I wired to basically take place of the bounce switch. Everything works fine, but when the switch is off I still read 5 or 6 volts across the hold relay. I’ve tried 3 different brand switches. This are all good quality switches rated at 10 to 15 amps. Is this just some false ghost voltage due to high multi meter impedance or do I have a problem? I’ve even ordered an analog meter to see if it makes a difference. I replaced the 2 cord plug with a 3 prong, but even with disconnecting the ground lug from the transformer I still get this stray voltage. Outlet tests ok.

Thanks

One of the issues with using a volt meter to measure 'stray voltage' is
that its very high impedance can give the impression that significant
power is present, when it is not.

At a pinball museum, we have had WPC pins side by side, one with a bad
ground, that gave 60V potential between them. They also gave the person
that warm fuzzy 'buzz' which is scary. Fixing the ground made that go away.

I would not worry too much about it. I would check to insure that your
SPST switch is turning off the hot side of the plug and not removing the neutral. If the plug is leaving the hot side going to the transformer,
you have a shock risk. Since you have converted to a 3 prong plug, you
will be certain that the hot consistently comes into one lead (assuming
your wall plug is wired correctly).

Another way to approach this would be to install a DPST switch. That
would remove both the hot and the neutral connections while leaving the
ground intact. I used to work for an instrument company in the 1980's.
At that time, UL in the USA required only a SPST switch. But Europe DIN required DPST switches, so we converted all to double pole. I noticed
that at some point, pinball machines went to double pole also.

--
http://orcalcoast.com/
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From Newsgroup: rec.games.pinball

Thanks for the info. I have the hot going to the fuse first. Coming out of the fuse I left that original wire and removed the 2 wires from the bounce switch. I extended those to the switch. Neutral is going directly to the transformer and not to the switch. The outlet wiring is correct. 120 volts between hot and ground. 0 between neutral and ground. You’re the 2nd person that said the high impedance of the voltmeter could be giving a false reading.
I’ve ordered an analog meter to see if it makes a difference.
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From Newsgroup: rec.games.pinball

Analog meter arrived today. It shows zero volts so it must be the high impedance of the digital meter giving me a ghost reading.
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From Newsgroup: rec.games.pinball

On 5/21/20 7:20 PM, Bob Monzo wrote:

Analog meter arrived today. It shows zero volts so it must be the high impedance of the digital meter giving me a ghost reading.

Yes, likely.

We used to call analog meters VOMs (volt ohm meters) and they put a significant load on a circuit and that can affect the reading. I had a
VOM and a VTVM (vacuum tube volt meter) which was very high impedance.
On some circuits, I had to use the VTVM to get a good reading.

I am glad those days have passed.

Another way to tell if there is significant power (or current) would be
to hook up a resistor, say 10K or 100K ohms, to the 'stray voltage' and
ground the other side. In effect, that is what your analog meter is
doing. Don't do that resistor test if you read a high AC voltage (like
120 VAC).

I usually don't worry until the voltage gets to be pretty high.

Most people I know just ground the spot to see what happens. With 6
VAC, about the only risk should be to blow a fuse.

But heck, I know electricians that kill the circuit they want to work on
by grounding the hot wire. I think that is nuts.

--
http://orcalcoast.com/
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From Newsgroup: rec.games.pinball

On Friday, May 22, 2020 at 2:59:44 PM UTC-4, LexingtonVAPin wrote:

On 5/21/20 7:20 PM, Bob Monzo wrote:

Analog meter arrived today. It shows zero volts so it must be the high impedance of the digital meter giving me a ghost reading.

Yes, likely.

We used to call analog meters VOMs (volt ohm meters) and they put a significant load on a circuit and that can affect the reading. I had a
VOM and a VTVM (vacuum tube volt meter) which was very high impedance.
On some circuits, I had to use the VTVM to get a good reading.

I am glad those days have passed.

Another way to tell if there is significant power (or current) would be
to hook up a resistor, say 10K or 100K ohms, to the 'stray voltage' and ground the other side. In effect, that is what your analog meter is
doing. Don't do that resistor test if you read a high AC voltage (like
120 VAC).

I usually don't worry until the voltage gets to be pretty high.

Most people I know just ground the spot to see what happens. With 6
VAC, about the only risk should be to blow a fuse.

But heck, I know electricians that kill the circuit they want to work on
by grounding the hot wire. I think that is nuts.

--
http://orcalcoast.com/

Thanks for your help. I’m going to leave it alone at this point.
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