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Topic: Why does my "ON" switch go both ways? |
J Hill
From:
Colorado, USA
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Posted 3 Jun 2021 10:01 am |
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I hope there's somebody here that appreciates an untypical question of curiousity once in a while, maybe if only for entertainment... 
My question is this: I've got a sort of large Evans Amp with a metal switch on the back. The "off" position is neutral (straight out) while pushing it to the Left... or the Right turns it on. Why is it made this way?
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"And now, Lord, what wait I for? my hope is in thee." (Psalms 39:7)
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Mullen S-10 the prettiest one ever made â¤ï¸ |
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Jack Hanson
From:
San Luis Valley, USA
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Posted 3 Jun 2021 10:05 am
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| Center position is "off." Left position and right position are both "on," reversing polarity. Basically eliminates the need for two separate "on/off" and "ground" switches. |
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David Nugent
From:
Gum Spring, Va.
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Posted 3 Jun 2021 11:46 am
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| If your amp is a hybrid (solid state pre amp, tube power section) this may apply. Normally on an all tube unit, the functions of the three way switch will be indicated as: 'Off', 'Standby, and 'On'. Solid state units do not normally require a warmup period which may account for the three way switch being wired with two 'On' positions. |
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George Biner
From:
Los Angeles, CA
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Posted 3 Jun 2021 9:01 pm
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It sounds like this is the power polarity switch found in old amps. With it, you could select which of the two power wires was acting as the hot and which the neutral (return) (before 3-wire plugs), the equivalent of turning the power plug 180 in the wall socket. One of these settings would give less hum than the other. The middle position functioned as "off".
The introduction of the 3-prong plug eliminated the need for it and any older amp with only two power wires should be upgraded to three to get a safety ground onto the chassis to prevent electrocution.
_________________
Guacamole Mafia - acoustic harmony duo
Electrical engineer / amp tech in West Los Angeles -- I fix Peaveys
"Now there is a snappy sounding instrument. That f****r really sings." - Jerry Garcia |
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J Hill
From:
Colorado, USA
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Posted 7 Jun 2021 3:18 pm
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Was I supposed to understand all that? 
_________________
"And now, Lord, what wait I for? my hope is in thee." (Psalms 39:7)
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Mullen S-10 the prettiest one ever made â¤ï¸ |
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Jim Pitman
From:
Waterbury Ctr. VT 05677 USA
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Posted 8 Jun 2021 3:20 am
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| J Hill, yes. |
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George Biner
From:
Los Angeles, CA
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Posted 8 Jun 2021 1:15 pm
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My main message is that the switch was designed like that to have a way to reduce hum. If you haven't done it already, you should have a 3-prong power cord put on it for safety, and then it won't matter what side you throw that switch to.
_________________
Guacamole Mafia - acoustic harmony duo
Electrical engineer / amp tech in West Los Angeles -- I fix Peaveys
"Now there is a snappy sounding instrument. That f****r really sings." - Jerry Garcia |
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