can someone explain this to me?

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jrmintz

Well-known member
Joined
Jun 4, 2004
Messages
998
Location
NY
Hi all,

I'm using http://sethglassman.com/MountainSwitch.pdf this Mountain Switch type B2 and the schematic for getting power to the neon bulb is confusing. How is this supposed to be hooked up? Is this calling for an external 33k resistor, and is 1/4 watt big enough? I understand that power comes into the center terminal, pin 2, and is sent to the transformer from pin 1. Help!
 
wow that drawing is pretty confusing.. it looks to me that the resistor is already in the switch. the drawing only shows 2 terminals.. does yours have 3?
 
Yes, mine has 3 terminals - 1 and 2 are silver colored and 3 is brass colored. It seems awfully dangerous to be hanging a resistor off the back of the switch at 125V, but I can't make heads or tails of it.
 
from what i've seen, 1-2 of course is the power contacting and 3 is the hookup for a ground to make the neon glow. I assume that the resistor is already in the switch since most of the ones i've used have one already in it.. with neons you can't ohm test it to find out! I suppose a peek inside is out of the question?
 
The use of the term "ground" is unfortunate. Do NOT connect ground to that switch!

The diagram is kind of confusing, but my best "read" of it is that the resistor and neon are already built in to the switch, Hot input goes to 1, hot output goes to 2, and neutral goes to 3. But this is just my own interpretation of the diagram. I would check it out with a current-limited supply (say, a 25W lightbulb in series with the Hot), an AC voltmeter, no load on the output of the switch and a great deal of care!
 
Usually, the resistor is already in there, and you wire it like this:
Lit-Switch.gif
 
> isn't neutral tied to ground in house AC wiring anyway?

Yes, BUT.

It is illegal and unsafe to put ANY current in the green wire in normal operation.

Green is there IN CASE insulation fails and some hot wire shorts to the chassis. Imagine the power transformer primary pokes through the paper insulation and touches the metal shell, which is bolted to the chassis. Without Green, the chassis may be at 120 volts. Touch it and die. With Green, if the chassis tries to get "hot", the fusebox fuse will blow, eliminating the hazard and forcing you to figure out what is wrong.

Anyway, in audio, a neon is generally a bad idea and dumping neon current into "ground" and case is STUPID. Neons BUZZ. They have a very square waveform. You don't want that garbage on your chassis and throughout your ground system.

A small detail: Black and White are often mixed-up. If you wire from Black to Green, then plug into a mis-wired outlet with Black and White reversed (60% of my kitchen was this way), the neon won't light.

Also: if you ever have to work with a GFI, neon current from Hot to Green will probably trip the GFI.

Don't treat White and Green as "interchangeable".

Yes, you "can" return the neon current to Green, it will light, it won't blow fuses. But don't.
 
Neon lamps are "noisy"... generates RFI. If you have sensitive preamp circuits in the box, it's going to pick it up. I'd use an LED or incandescent lamp instead.
 
Again, thanks guys. I've wired it as per PRR's drawing, and from a power standpoint it's fine. From an audio standpoint it's not, and now I'm wondering if it's the neon. I'll replace it tomorrow and see if things work better.

:thumb: :thumb:
 

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