[Amps] 3-500Z heater voltage reduction

[Alek Petkovic]

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 at 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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