(Topic ID: 251099)

Phantom Voltage in Disconnected Chime Circuit???


By JethroP

8 days ago



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  • 8 posts
  • 3 Pinsiders participating
  • Latest reply 4 days ago by wayout440
  • No one calls this topic a favorite

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Continuity Check (resized).png
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#1 8 days ago

Found a burned up chime coil in Spanish Eyes. Upon investigating I disconnected the coil and measured the voltage to the coil (unterminated wires) and there was correctly 26V when the 100 point or 1000 point switches closed, but with the switches open I measured about 12 volts. I have checked the continuity from the chime coil lead (B-G) to the yellow (power) wire and when the relay switches are open there is no continuity. Why am I reading 12 volts on this open circuit? Is this some kind of induced voltage due to the wiring, or what?

Screen Shot 2019-09-09 at 7.34.18 AM (resized).png
#2 7 days ago
Quoted from JethroP:

Why am I reading 12 volts on this open circuit? Is this some kind of induced voltage due to the wiring, or what?[quoted image]

There can't be "induced voltage" unless current is flowing. Assuming everything wired per the schematic, the specific circuit is an open with both switches open, and there is no current flowing. Measuring in a static circuit, voltage is a potential difference. Where exactly are you putting your test probe points?

#3 7 days ago

Does this answer your questions about where I measured the continuity and voltage? I am measuring 12v at the wires that would otherwise be connected to the chime coil, but I have it removed.

Continuity Check (resized).pngTest Probe Location (resized).png
#4 7 days ago

Basically, if the switches are truly open then the wires between the switches and coil are essentially floating in space and there is no voltage thete, you wouldn't see any kind of voltage at those points. Imo you probably have a short somewhere.

#5 6 days ago
Quoted from wayout440:

Basically, if the switches are truly open then the wires between the switches and coil are essentially floating in space and there is no voltage thete, you wouldn't see any kind of voltage at those points. Imo you probably have a short somewhere.

Induced voltage can occur when wires are merely in close proximity a hot conductor in an AC circuit. My question, to others: have you ever seen this in your pinball machine?

#6 6 days ago

So what happens when you short the coils of the chime coil? Use your amp meter setting and probes to short the lugs to see current draw with the meter fuse as circuit protection. If indeed you are getting induced voltage readings no current will flow. If you have a short you may blow your meter fuse, but you will learn it isn't an induced voltage reading.

Personally I would lift the 100 and 1000 switch leaf wires one at a time and measure voltage to determine which relay is causing the voltage reading.

#7 5 days ago

When the switches are open, I confirmed there is no current flow and I measure about 12VAC to the coil. OK, so I received the new coil and installed it and everything is working fine. I'd never seen induced or phantom voltage like this before. I wonder if it has anything to do with me installing a 3 conductor power cord and grounding the neutral.

#8 4 days ago
Quoted from JethroP:

I'd never seen induced or phantom voltage like this before. I wonder if it has anything to do with me installing a 3 conductor power cord and grounding the neutral.

Probably has more to do with your meter.
https://m.grainger.com/content/safety-ghost-voltages

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