View Single Post
  #14  
Old 10-21-2014, 03:02 PM
DavGoodlin's Avatar
DavGoodlin DavGoodlin is offline
Motorola Minion
 
Join Date: Aug 2011
Location: near Strasburg PA
Posts: 3,501
I have most of those tubes but did not know what they went in.

One caution I have read about farm sets is that, when you have the tubes warm, never switch it off then back on right away.

For "A" battery: The 2 volt tube heaters are usually in parallel and will load two D cells with only 300 ma of current based on the tube data, so you will need a dropping resistor of about 1.6 ohms.

For "B" battery: Daisy chain eight 9-volt batteries together, you'll have enough current to drive the tube plates.
I have a Sears 757.421 mini-tube "pocket radio" from 1955 that only needs 45 Volts, but all those batteries will not fit inside

What makes battery-tube sets fun for nighttime DX is, you can take them outside far from buildings and 120 volt line interference!
__________________
"When resistors increase in value, they're worthless"
-Dave G

Last edited by DavGoodlin; 10-22-2014 at 08:23 AM. Reason: add B voltage
Reply With Quote