[Boatanchors] Reduced filament voltages (Re: Boatanchors Digest, Vol 87, Issue 30)

[Henry Mei'l's]

Dave,

If your  filament/power transformer isn't encased and there's space between 
the laminatedcore and the windings, much easier if your using a torroid 
unit, you could simply add an additional 2.5 volt winding  - I've added low 
voltage windings to older transformers and some of my torroid units.

Henry
oz3o n2nr

----- Original Message ----- 
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> Today's Topics:
>
>   3. Reducing filament voltage (David Knepper)
>   4. Re: Reducing filament voltage (mac)
>
>
> Message: 3
> Date: Sat, 16 Apr 2011 16:55:37 -0400
> From: "David Knepper" <collinsradio at comcast.net>
> Subject: [Boatanchors] Reducing filament voltage
> To: <amateur-repairs at yahoogroups.com>
> Cc: boatanchors at mailman.qth.net
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> I am finishing the wiring on my Collins 4A (circa. 1934) transmitter.
>
> The problem is to produce 2.5 volts for the 47 volt oscillator tube.  The
> newer transformer that I am using has a 6.3 volt winding.  Someone told me
> about using a couple of 1N4007 in series from the filament lead to the pin
> socket.
>
> I am sure that somone will tell me to use a series resistor or use a later
> tube with a 6 volt filament.  What tube might that be to replace the 47
> tube?
>
> Any ideas?
>
> Thank you
> David Knepper, W3CRA/W3ST
> Editor of the Collins Journal
> Secretary of the Collins Radio Association
> www.collinsra.com
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> ------------------------------
>
> Message: 4
> Date: Sat, 16 Apr 2011 14:06:50 -0700
> From: mac <w7qho at aol.com>
> Subject: Re: [Boatanchors] Reducing filament voltage
> To: "David Knepper" <collinsradio at comcast.net>
> Cc: amateur-repairs at yahoogroups.com, boatanchors at mailman.qth.net
> Message-ID: <7CE95C89-83B7-4688-A7C8-6554F74BD97F at aol.com>
> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes
>
> David,
>
> Let me be the first to recommend a series resistor.
>
> The only 6.3 volt tube I find with the same base connections is the
> 6A4 which has similar but somewhat lower element voltage and current
> ratings.
>
>
> Dennis D. W7QHO
> Glendale, CA
>
> ****************
>
> On Apr 16, 2011, at 1:55 PM, David Knepper wrote:
>
>> I am finishing the wiring on my Collins 4A (circa. 1934) transmitter.
>>
>> The problem is to produce 2.5 volts for the 47 volt oscillator
>> tube.  The
>> newer transformer that I am using has a 6.3 volt winding.  Someone
>> told me
>> about using a couple of 1N4007 in series from the filament lead to
>> the pin
>> socket.
>>
>> I am sure that somone will tell me to use a series resistor or use a
>> later
>> tube with a 6 volt filament.  What tube might that be to replace the
>> 47
>> tube?
>>
>> Any ideas?
>>
>> Thank you
>> David Knepper, W3CRA/W3ST
>> Editor of the Collins Journal
>> Secretary of the Collins Radio Association
>> Rodger WQ9E
>
>