Using small wire will eventually anneal it and change the resistance during
the process. Better to use the proper size. And its 30A, not 15 for 2 tubes.
Carl
KM1H
----- Original Message -----
From: "Alek Petkovic" <vk6apk@bigpond.com>
To: <amps@contesting.com>
Sent: Tuesday, September 15, 2009 6:50 PM
Subject: Re: [Amps] 3-500Z heater voltage reduction
> No, you want to drop it by 2 Volts. With 1 Volt, you are still 10%
> high. That's way too much!
>
> To destroy 2 Volts at 15 Amps so you need a resistance of 0.133 Ohms
> in series with the filaments. The resistor will be dissipating 30
> Watts. 8pcs x 1 Ohm/10W wire wound resistors in parallel gives you
> 0.125 Ohms (1.875V drop) and 7 in parallel gives you 0.143 Ohms
> (2.145V drop) with plenty of dissipation headroom.
>
> Alternatively you could use some lengths of smaller gauge wire in
> series with the filaments to lose the 2 Volts but remember that you
> are dissipating 30 Watts continuously so make sure you don't melt or
> burn anything.
>
> Once again, don't settle for 1 Volt drop.
>
> 73, Alek
> VK6APK
>
>
> At 03:03 AM 16/09/2009, MIKE DURKIN wrote:
>
>>Ok.. yea i did search some on reducing the voltage at the heaters on
>>google ... yikes alot of what in not really looking for.So a quick
>>question .. what is the favored way to reduce the voltage ?? i have
>>12V ac across 2@3-500z's and i want to drop it by -- say 1 volt.
>>Trying to keep to the confines of what i have around .. some 12 and
>>10Ga solid magnet wire, some romex (120v stuff) and some 12ga hookup
>>wire witch i dont think the insulation is rated for heat at all ....
>>Or some other common junk drawer stuff that would do the trick ...
>>the last thing i tried was a .27Ohm 10W cement resistor and that was
>>too high of a resistance ( was a bit surprised but oh well i dont
>>know the internal resistance if the filaments anyways)
>>KC7NOA ... i think i even have some nichrome sitting round some where.....
>>
>>
>>
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>
> http://www.qrz.com/db/vk6apk
> http://www.qrz.com/db/vk6py
>
>
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