I am building an arcade machine, using a CRT television. I am wishing to replace the television's front panel power switch with a toggle switch on the outside of the cabinet but am concerned by two pins on the switch.

The two smaller pins mounted on the black plastic at the top are momentarily connected after the button is depressed but not after the unit is powered off or on. The switch indicates that they have a maximum voltage of 24v.

Is this some sort of protection mechanism?

Would I be unwise to wire a new switch without this?

Finally, is there any reason why I couldn't just keep the switch turned on and instead just use a master switch which turns on mains voltage to the whole unit? Is the television likely to be damaged if I don't turn it on and off using this front panel switch?

TV power switch


Here is a photo of the circuit board and the CRT. The switch in question is a PREH ME5C.

I replaced the switch as intended and the TV turns on with no apparent ill-effects. Interestingly, the on indicator LED briefly flashed on but then turned off.

Is the 24V possibly a secondary circuit for the remote control and front panel? I don't have the remote and I'm not game to reach inside the unit while it's on to play with the buttons on the front panel.

Circuit board and CRT

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    \$\begingroup\$ What does the TV manual say about turning the TV on and off? \$\endgroup\$ – Andy aka Aug 10 '17 at 9:22
  • \$\begingroup\$ I got the unit for $10 from a second hand shop. It came with no manual. \$\endgroup\$ – nullPainter Aug 10 '17 at 9:30
  • \$\begingroup\$ So, go google it. \$\endgroup\$ – Andy aka Aug 10 '17 at 9:31
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    \$\begingroup\$ I don't even know what make or model it is. I have the innards and nothing else. Are you being obtuse because you think this is a lazy question or is the answer purely dependent on the specific design of the television? I asked because I assumed there was some general wisdom in this area. \$\endgroup\$ – nullPainter Aug 10 '17 at 9:38
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    \$\begingroup\$ This is by any chance a mixed 230V/24V CRT? If not, that contact could be a "reverse pilot", which closes a bit after the mains voltage to prevent the turn-on speaker POP. \$\endgroup\$ – Janka Aug 10 '17 at 10:11

Could this switch operate the degaussing coils? A lot of CRT televisions and monitors would automatically operate the degaussing coils when turned on, rather than the user having to manually operate a control.

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    \$\begingroup\$ Degauss is controlled by a PTC posistor \$\endgroup\$ – pasaba por aqui Aug 10 '17 at 11:24

From what I can see from similar looking mains television switches, this appears a common design to provide momentary current to circuitry which performs the same function as powering on the television through the remote. I am going to infer from this that this can stay unconnected as I don't currently require a remote to get a signal on the television.


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