My goof!
Carl
----- Original Message -----
From: "Alek Petkovic" <vk6apk@bigpond.com>
To: "Carl" <km1h@jeremy.mv.com>; <amps@contesting.com>
Sent: Tuesday, September 15, 2009 7:54 PM
Subject: Re: [Amps] 3-500Z heater voltage reduction
> Yeah, you are right about the 30A for 2 tubes but this fellow mentioned
> that he measured 12V across the filaments so I assumed he was running them
> in series which gets us back to the 15A value.
>
> 73, Alek.
>
>
> At 07:48 AM 16/09/2009, Carl wrote:
>>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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>
>
> http://www.qrz.com/db/vk6apk
> http://www.qrz.com/db/vk6py
>
>
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