[R-390] R-392

[Jim Whartenby]

Since the R-390A/URR cost reduction program deleted the high heat generating regulated power supply used in the R-390/URR, has anyone considered removing the regulated power supply circuit from the audio module and installing two 6H chokes and suitable electrolytic capacitors in place of the 6082 tubes?  

The end result will be very close to the 180 or so volt B+ seen in the R-390A/URR.  Also solid-stating the power transformer rectifiers will reduce more waste heat generated in the receiver.  Total savings is close to 80 watts doing a back of the envelope calculation which is almost half of the power consumed by the R-390/URR.  Thoughts?
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.  Murphy 

    On Monday, October 6, 2025 at 11:23:54 AM CDT, Jacques Fortin <jacques.f at videotron.ca> wrote:   

 Hello Les,

I have some comments about the R-390/URR...
I agree that the 47 ohms resistors fitted on the cathodes of the 6082 pass tubes surely needs to be changed.
5W parts can be used there.
But, IMHO, the same value resistors fitted on the cathodes of the rectifier tubes need to be replaced too.
For the rest of the parts within, all depend on the conditions that the R-390 unit was used and stored.
I found many of the Allen-Bradley carbon film resistors in mine that were completely off tolerance and I had to replace those, especially the 2.2k ohms that feed the plates of the IF amplifier stages.
I also agree that most of the capacitors used within cause no problems, being Sprague Vitamin-Q types.
Except if you find some with traces of oil on their ends: that means that the gas-tight seal have failed and the internal "oil" has been contaminated with oxygen, which result in the well-known PIO "leakage" syndrome.
I had to replace some in my unit (1st contract Collins, sn 2074) but no more than 4 or 5, all in the IF module.
And yes, fitting a solid state HV regulator in is a good idea !

73, Jacques, VE2JFE in Montreal

The only "problems" connected to the R-390/URR are the 47 Ohm resistors under the chassis, four of them if my memory is right.
They are usually slightly charred from heat... 
There is a solid state  kit available that reduces the heat from the PS. Google it. 
No problem caps. Remember this
wasn't a cost reduced receiver like the R-390A. 
Les
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