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
<[email protected]> 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
______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[email protected]
This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
