A friend recently got stiffed from that source for an 8877 filament
xfmr, it was almost $100. He didnt think to check out the $33 Hammond.
Carl
KM1H
----- Original Message -----
From: "Bob Maser" <bmaser@tampabay.rr.com>
To: "Carl" <km1h@jeremy.mv.com>; "Paul Decker" <kg7hf@comcast.net>;
<amps@contesting.com>
Sent: Friday, May 15, 2009 7:36 PM
Subject: Re: [Amps] filament transformers
> 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
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Amps mailing list
>>> Amps@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>>
>>
>> _______________________________________________
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>
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