[Hallicrafters] Ref: SX28 xfmr

[Roy Morgan]

On Apr 15, 2010, at 11:42 AM, Walt Cates wrote:
> ... I don't know what the current requirements for the 28 are. If  
> 40ma high voltage and 2A @ 5vac and 2A @ 6.3vac will work the  
> HX237AZ is $30 cheaper.


SX-28 folks,

The (military) manual for the SX-28A shows:

6.3 volts at 4.8 amps
270 vdc at 150 ma.


If such manual information is not at hand, just go through the list of  
tubes and tally up the filament currents and normal operation plate  
currents.

Very rough approximations might be:

The rectifier is a 5Z3, so it's normal operation rating for current  
can be used as a rough guide.
The radio has two 6V6's in the audio, and they might operate at 30 ma  
each - do ohms law on the voltage at their cathodes and the self-bias  
resistor value.  (So the 40 ma is not enough by a lot.)  IF, RF and  
audio amp tube often run at 8 to 10 ma each, mixers about the same.   
Screen currents might be ignored in an approximation.


About rectifiers:
5U4's take 3 amps filament (If I remember right)
5Y3's use 2 amps but won't do 150 ma I think
5R4's use 2 amps but have surprisingly high DC rating
5Z3 may be similar

Roy



Roy Morgan
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