Thread: Lang radio
View Single Post
  #2  
Old 10-02-2017, 09:22 PM
init4fun's Avatar
init4fun init4fun is offline
VideoKarma Member
 
Join Date: Mar 2011
Posts: 1,169
Unhappy Post Response

Hello my Friend . Looking at you photos my best guess would be that it was built to operate from 32 volt DC "farm power" since as you noted there is no power transformer . Either that or there was a power unit that was separate from that chassis that is no longer with it . Looking at the tubes and more importantly the transformers and coils underneath it , it looks like a 3 tube "TRF" (Tuned Radio Frequency instead of superhetrodyne) set with 3 stages of AF amps to give enough signal to power one of the horn speakers of the day rather than a set of headphones .

Such sets are usually real simple to get going since there isn't a lot to them , just a daisy chain of RF amps that all get tuned to the desired received frequency and of course the three audio stages to get the signal big enough to drive the speaker . So it needs a speaker , and to provide it with the appropriate voltage(s)* , give it as long of an antenna as you can possibly set up plus another 50 feet , and with a good ground you may just be able to pull in a few of your local AM stations , barring of course the RF noise level in your area . Last time I had an operational TRF set on display it would get the nearest strongest 4 or 5 stations depending on time of day .

* The two power connections only deal kinda throws me , cause those sets , whether 32 volt farm set 110 VAC , had to have at least ;

An "A" supply , this was power to heat the tube's filaments (cathodes) and was usually a 6 volt DC source regulated with a rheostat .

A "B" supply , this was power to the tube's plates (anodes) and was usually anywhere between 45 and 90 volts DC .

And lastly a "C" supply , this was a negative bias voltage applied to the tube's grid that was used to keep the grid about 4 or so volts negative with respect to the cathode .

Now , the kicker here is that I don't see the voltage divider network that would be needed to derive those three voltages from the single two connection power source as seen in the photos . Clearer photos of all the wiring underneath would be helpful in determining exactly how the different needed voltages are gonna get to the tubes .

PS , can anybody else see the little purple frowning emoji at the top of my post here next to where it says "Post Response" ? I did not click on that or intentionally put it there and I can't seem to edit it out ? Is that some kind of software bug or is there some way I can get rid of it ?

Last edited by init4fun; 10-02-2017 at 09:35 PM. Reason: trying to get rid of that damn frowning face ......
Reply With Quote