[Milsurplus] RAK-RAL question

[brunneraa1p at comcast.net]

 From: Robert Nickels <W9RAN at oneradio.net>
> I've got the RAK-7 and RAL-7 and would like to hook them up (switchable) 
> to a common power supply.  I can't seem to find the docs I thought I 
> had, but figured someone here would know the answer right off.
> 
> Does the CND 23072 control unit do this?  It's got two power switches 
> and one for audio, and says it's "for use with RAK-7 and RAL-7".  Yet I 
> seem to remember the Navy required a separate (big, honkin' heavy) CND 
> 20131 Rectifier Power Unit for each receiver.   I'd like to switch the 
> one I have between the two, although I'm tempted to lose it and just use 
> a small power supply that'll do the job with way less overkill. 

The RAK and RAL run very well at 180 volts, about 30-35 ma, and 90 volts regulated at less than 1 ma.  Load current varies somewhat with rf gain setting, and certainly not more than 40 ma.  6.3 volt heater current is 2 Amps.  The audio filter inductors pick up a wee bit of hum from the heater wiring, so dc is best.  
If you make a regulated 180 volt supply, you don't need the 90 volt feed, as there is an internal dropping resistor for the 90 volts.

The CND-20131 power supply unit transformer looks heavy enough to feed both receivers, (but I haven't tried it) especially if the heaters are fed from another source.  The filter chokes also look large enough for both receivers.  There is a huge ballast tube and resistor on the input which we don't need, and I doubt worked well in the first place.  There are taps for 110, 115, and 120 volt input.  The design looks strange to me, as they pass 35 ma through the 874 90 volt regulator to regulate less than 1 ma, and the carbon dropping resistors are running near full rating in a poorly ventilated place and are likely toast.  I cut the regulator current to about 5 ma, and it works fine.  If your 874 regulator isn't regulating, there is space for an OB3/VR-90 plus octal to 4-prong adapter. 

The CND-23072 control box switches ac to the two CND-20131 power supplies, and switches audio from each receiver, or both in parallel.  I think they are rare.  

Richard Brunner, AA1P