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.....
>>>
>>>
>>>
>>>_________________________________________________________________
>>>Hotmail: Powerful Free email with security by Microsoft.
>>>http://clk.atdmt.com/GBL/go/171222986/direct/01/
>>>_______________________________________________
>>>Amps mailing list
>>>Amps@contesting.com
>>>http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>>http://www.qrz.com/db/vk6apk
>>http://www.qrz.com/db/vk6py
>>
>>
>>_______________________________________________
>>Amps mailing list
>>Amps@contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
http://www.qrz.com/db/vk6apk
http://www.qrz.com/db/vk6py
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|