[R-390] R-391 restoration update

[Al Solway]

Hi Paul,

Thanks for the update. Very interesting comments and observations. I
will keep this info in mind when I get to the "Power On" phase in the
restoration of my R-390. 


"Paul H. Anderson" wrote:


> Knowing what I know (or think I know) now, I do believe I'd just replace
> every cap and resistor in the AF deck before worrrying about trying to use
> it.  Even resistors on the board near the 6082 tubes were fried to a
> crisp.  I don't think I'd apply this same strategy to the IF deck, but if
> I start replacing capacitors there, I'm gonna do all the resistors, too -
> they just drift too much from heat, like from the soldering iron.
> 
> Paul

I completed an R-390A about a year ago. I did not apply power to this
radio until out of spec resistors, paper/black beauty caps, visual
defects and cleaning and lubrication was completed. At power on there
were no electrical problems except for two mechanical alignment
problems. I mention this because of the cumulative effects of the out of
spec resistors and the known problems with the caps in the R-390A
contribute to the initial electrical problems in restoration. 

The R-390 I am working has 36 out of spec resistor, 20 in the IF module.
I will not replace any caps because it is not necessary in the none A
because of the better quality caps used. This is not my observation but
that of others who have made this recommendation on this reflector. All
cleaning is complete. Waiting for spring so that the front panel can be
stripped and painted. My paint shop is the balcony of the my apartment.

The experts recommend replacing all the 47 Ohm resistor. I replaced them
in the 6082 cathodes although they were in spec. The ones in the 26Z5s
were burnt completely open, charred to a crisp. I am using the white
sand 5 watt resistors. They fit nicely in the original 47 Ohm location.

BTW Barry Hauser mentions replacing the 6082s with a solid state device
in his response to this post. I have made an agreement with Barry to
build a solid state replacement for the 6082s and write an article on
the construction for Hollow State News. The circuit is detailed by Dr.
Gerald N. Johnson, K0CQ, in Hollow State News, Issue #52, Spring 2001.
The article will be completed in the late summer after all testing is
completed.

Barry if you read this everything is going well with the module. A PWB
has been made, a heat sink selected. I have all components except for
the 180 and 200 Volt Zeners. They are on order and should be here next
week. The module will plug into the two 6082 sockets. No fan is
contemplated at this time but I will be contacting Dr. Jerry with a
couple of related technical questions. I am not an engineer but an aging
tech with a bit of experience. Need good engineering input so that no
mistakes are made.

Sorry Paul but I digress from the original topic. A final comment and I
am sure that you are aware of it. Use heat sinks on good components when
removing components that are tied to a common point. This will prevent
damage to good components. Those carbon resistors are very susceptible
to heat. 

Good luck with the R-391.

Al 



> _______________________________________________
> R-390 mailing list
> R-390@mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/r-390