[R-390] R-390 mods and weak points

Cecil chacuff at cableone.net
Thu Dec 6 16:33:11 EST 2012


The 47 ohm resisters are in the R-390/URR.  There are 4 of them that usually need to be replaced.  I usually up size them to 5 watt.  The caps are high quality and are usually not a problem but do fail from time to time.  There is no death cap issues in the R-390 as there are no mechanical filters...it's all L/C filtering which is what makes it sound a good bit better.

The slug rack cores are unique to the R-390 and are not interchangeable with cores from an "A".  Also don't mix them up in the radio....they are color coded....make note of that on disassembly.  The power supply filters are oil caps....usually good also.  

All else is pretty standard.....and the green gear thing is way over blown....it's not necessary especially if you are doing a rebuild...mainly a convenience if doing simple maintenance.

Cecil

Sent from my iPad

On Dec 6, 2012, at 2:13 PM, Robert Newberry <N1XBM at amsat.org> wrote:

> I've been reading various websites and archived threads. I have a non A
> R-390 that is all torn down to individual modules. My questions are.
> 
> Is there any caps or resistors that should be checked or replaced? I've
> read alot about "death caps" and 47 ohm resistors but everyone was talking
> about R-390A.
> 
> Are there any recommended mods? For example I've read about fatting up caps
> in the audio module to get more low end audio. Although these were
> referenced to the R-390A. I'm all set with the inrush mod for slower start
> up and hanging a fan to aid with cooling.
> 
> Thank you
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