Re: 6.0 volt Filament

Jimmie D wrote:

"Jimmie D" <GFENDER@xxxxxxxxxxxxxxx> wrote in message
news:47314c55$0$25104$4c368faf@xxxxxxxxxxxxxxxxx
Im trying to build a n amp using 4cx250s and need 6.0 volts for the
filament. The only transformers I have are 6.3. Can I just use a ballast
resistor to drop it down. My other thought was to wire another 6.3 volt
transformer as an autotransformer to reduce the voltage and use this to
feed the filament transformer.

Jimmie


I found an 8VAC 10 amp transformer I think I am going to use this because I
can use it with practical sized ballast resistors to limit turn on surge.
Can anyone think of a reason not to do this?

The larger the dropper resistor, the more the heater voltage will vary with mains voltage. It isn't a large effect, but the manufacturer's tolerance on heater voltage is only +/-5% (in this case, 5.7-6.3V).

The final answer will depend on the stability of your mains voltage, measured right at the amplifier. Part of this will depend on the utility company, and part will depend on your local wiring because the B+ supply will tend to pull the voltage down.


--

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek
.

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