Waste money on a custom filament transformer? I'm not talking about a $100
transformer, maybe $35. If you can't afford that maybe you shouldn't be
building homebrew amps.
Bob W6TR
----- Original Message -----
From: "Carl" <km1h@jeremy.mv.com>
To: "Paul Decker" <kg7hf@comcast.net>; <amps@contesting.com>
Sent: Friday, May 15, 2009 6:58 PM
Subject: Re: [Amps] filament transformers
> Get the 3A version and measure the voltage at the socket. If its high
> (which it should be) wind some wire on a small ferrite rod which can
> also double as a filament choke. When you go to the 2nd tube use heavier
> wire on the rod or none depending on the voltage. It never hurts to go
> slightly lower than the median spec. The transformer will only give 14V
> at its 3A rating and it will be a bit higher at 1.5A
>
> Dont waste money on an overpriced custom transformer in this instance. I
> dont see the necessity for a rheostat either for such a small drop.
>
> Carl
> KM1H
>
>
>
> ----- Original Message -----
> From: "Paul Decker" <kg7hf@comcast.net>
> To: <amps@contesting.com>
> Sent: Friday, May 15, 2009 4:40 PM
> Subject: [Amps] filament transformers
>
>
>>
>>
>> Hello builders,
>>
>>
>>
>> My amp continues to grow. I'm trying to pick out a filament
>> transformer, such and easy task.
>>
>>
>>
>> The amp is based on a 3cx800a7 which requires 13.5V +- 0.6V at 1.5A. I
>> was thinking that a 14V transformer would work great. Ideally, I would
>> like to build the amp with the option to eventually be expanded to a
>> pair of 3cx800's rather than the single. This would mean I need 3.0A
>>
>>
>>
>> On digikey , they have a 14V 3.0A transformer
>>
>> http ://search. digikey .com/scripts/ DkSearch / dksus . dll
>> ?Detail&name=237-1279-ND
>>
>>
>>
>> and a 14V 4.0A transformer
>>
>> http ://search. digikey .com/scripts/ DkSearch / dksus . dll
>> ?Detail&name=237-1094-ND
>>
>>
>>
>>
>>
>> So my questions are: Is it acceptable to use the higher current rating
>> in the single tube version of the amp? Would current inrush be an
>> issue? Is the 3A version enough, should I get the 4A version or
>> something even larger? Or, is there something else I should be
>> thinking about using?
>>
>>
>>
>> thanks,
>>
>> Paul, kg7hf
>>
>>
>>
>>
>>
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>>
>
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