volt dropper

12/23/2009 9:33:23 AMfrank goddard

Gentlemen,

With a 110 volt supply and tube heater train of 37 volts at 0.3 amps what value dropper resistor do you recommend
and what wattage should the dropper be. Would you recommend the use of a capacitor in lieu of a dropper,

many thanks,

Frank Goddard. Doncaster England.

12/23/2009 10:18:14 AMDoug Criner

A dropping resistor isn't the ideal solution:

110 - 37 = 73V drop

R = 73/0.3 = 243 ohms

P = 73 x 0.3 = 22 W

That dropping resistor will need to be rated 50W for safety margin. It will put out mucho heat - couldn't be installed in or near the radio.

Best to use a filament transformer. A capacitor would work.

12/24/2009 1:38:37 PMEd M

:A dropping resistor isn't the ideal solution:
:
:110 - 37 = 73V drop
:
:R = 73/0.3 = 243 ohms
:
:P = 73 x 0.3 = 22 W
:
:That dropping resistor will need to be rated 50W for safety margin. It will put out mucho heat - couldn't be installed in or near the radio.
:
:Best to use a filament transformer. A capacitor would work.
:

12/25/2009 2:45:44 PMPeter G. Balazsy

Assuming 125v incoming AC line and 37 volt @ 300ma heater string... you can use a 6.8uf non polarized 250vAC dropper cap.... you can also add a 10 ohm 2 watt surge resistor in series with it.

That will do the job nicely.

12/27/2009 2:27:55 PMfrank goddard

:Assuming 125v incoming AC line and 37 volt @ 300ma heater string... you can use a 6.8uf non polarized 250vAC dropper cap.... you can also add a 10 ohm 2 watt surge resistor in series with it.
:
:That will do the job nicely.
:

12/27/2009 2:29:37 PMfrank goddard

Many thanks gents. You have all talked me out of a dropper. I do not have a transformer to hand so it looks like the transformer method.

Hope you all had a good workshop christmas. Frank

::Assuming 125v incoming AC line and 37 volt @ 300ma heater string... you can use a 6.8uf non polarized 250vAC dropper cap.... you can also add a 10 ohm 2 watt surge resistor in series with it.
::
::That will do the job nicely.
::
:

12/27/2009 3:38:50 PMLewis L

:
:Many thanks gents. You have all talked me out of a dropper. I do not have a transformer to hand so it looks like the transformer method.
:
:Hope you all had a good workshop christmas. Frank
:
:

There are many places on the Internet that will give you all the info you need on using a capacitor to drop Voltage. Try Google and you can find what you want somewhere if you look long enopugh.
Lewis
:
:
:::Assuming 125v incoming AC line and 37 volt @ 300ma heater string... you can use a 6.8uf non polarized 250vAC dropper cap.... you can also add a 10 ohm 2 watt surge resistor in series with it.
:::
:::That will do the job nicely.
:::
::
:

12/28/2009 3:15:53 PMfrank goddard

::OOOPS! I MEANT CAPACITOR METHOD

FRANK

::Many thanks gents. You have all talked me out of a dropper. I do not have a transformer to hand so it looks like the transformer method.
::
::Hope you all had a good workshop christmas. Frank
::
::
:
:There are many places on the Internet that will give you all the info you need on using a capacitor to drop Voltage. Try Google and you can find what you want somewhere if you look long enopugh.
:Lewis
::
::
::::Assuming 125v incoming AC line and 37 volt @ 300ma heater string... you can use a 6.8uf non polarized 250vAC dropper cap.... you can also add a 10 ohm 2 watt surge resistor in series with it.
::::
::::That will do the job nicely.
::::
:::
::
: