[R-390] R-391 restoration update

[Paul H. Anderson]

On Wed, 27 Feb 2002, Al Solway wrote:

> > 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.

Hmm... I may need to beg to differ.  At the least, in the AF deck, there
perhaps 4 caps that get toasted enough to cause problems, and between the
AF and IF deck, there are a number of electrolytic caps, some of which
have been replaced in earlier lives, and some of which were leaking when I
got them.

One of my 390 IF decks has what looks to be leaking or corroded .01uF
tubular caps - only a few, but some nonetheless.  If I were replacing
resistors down inside there (ow), I think I'd find nice fitting caps and
replace them as well.

> This is not my observation but
> that of others who have made this recommendation on this reflector.

> 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.

Oops, I think I used 2W flame proof ones.  They look to be holding up, but
I haven't used it a lot yet, either.  At any rate, yes, they get toasted
everywhere I've seen (2 PS, 2 AF decks).

> 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. 

A welcome diversion, don't worry!

This is a technique I haven't tried much of yet.  I've been aware of it,
and the need to do it, but the times when it was an issue, I felt I didn't
even have enough dexterity to get another piece of metal down there in the
morass of wires.

> Good luck with the R-391.

Thanks, and likewise for your fine 390!

Paul