Panel Light

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loupy31
Posts: 50
Joined: Thu Jan 28, 2010 9:08 pm

Panel Light

Post by loupy31 »

Hi All,
I have a Panel light for my TW Xpress build, Its is a 120vac, I am in australia and my PT is a 240vac, What resistor value do i need to make it compatable with 240vac.

Regards Peter
Cliff Schecht
Posts: 2629
Joined: Wed Dec 30, 2009 7:32 am
Location: Austin
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Re: Panel Light

Post by Cliff Schecht »

You need the full operating temperature current draw of the pilot light to know what the resistor value should be. If you know this then the calculation is simply R=(240V-120V)/I, where I is current the light draws. The problem is that if the pilot light draws more than 50mA of current then you're looking at at least a 10W resistor and a big waste of power (although tube amps in general are a big waste of power ;)).
Cliff Schecht - Circuit P.I.
paulster
Posts: 1299
Joined: Tue Oct 10, 2006 5:08 pm
Location: Los Angeles & London

Re: Panel Light

Post by paulster »

Do you have a dual-primary PT, with 2x 120V primaries in series?

If so then just parallel the lamp across one of the primaries and it'll run happily at 120V.
loupy31
Posts: 50
Joined: Thu Jan 28, 2010 9:08 pm

Re: Panel Light

Post by loupy31 »

My PT has 0, 100, 120, 220, 230, 240, taps, if I use 0 and 120, will that work ok?

peter
paulster
Posts: 1299
Joined: Tue Oct 10, 2006 5:08 pm
Location: Los Angeles & London

Re: Panel Light

Post by paulster »

Yep, that'll work fine.
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