[R-390] No "Depot Dawg"

[Philip B Atchley]

Hi Bob.

Thanks for the good info.  As to the "Cool factor".  Hey, to someone who
grew up during the "Happy Days era" (born Aug '43) "cool" is important
8^)

73 de Phil  KO6BB

> I guess this is what makes it a hobby. I would vote with you - a 
> unit that
> is "all original" is slightly cooler than one with mixed modules. 
> That's not
> to say better or more functional, just cooler. Needless to say this 
> issue
> has come up before. Of course with very few exceptions (say 10 
> radios) there
> is no way to *ever* prove that a radio is original so you never 
> really know.
> 
> The metal/glass package capacitors are better than the black plastic 
> package
> ones. The yellow plastic wrapped ones are Mylar (or similar) with a 
> plastic
> insulation. About the only disadvantage to the yellow ones is that 
> when you
> hit them with a soldering iron they melt.
> 
> The thing that makes the black or brown caps a problem is that the
> insulation is paper (or paper with mica in it). The stuff soaks up 
> humidity
> and then they get leaky. The whole process really gets going when 
> the case
> splits open.
> 
> Leaky capacitors aren't all that hard to check. You can use a fairly 
> simple
> setup. Get as sensitive a meter dc meter as you can find. A good old 
> Weston
> or Simpson analog meter works well. If you can find something in the 
> 10 or
> 20 ua range that should do. Then set up about a 100 volt power 
> supply.
> Stacking two 48 volt units is one approach. One microampere at 100 
> volts
> works out to 100 meg ohms. A 10 meg ohm series resistor will keep 
> you from
> blowing out the meter. New from the old box plastic capacitors will 
> all read
> "no deflection" on the meter. Every black or brown body cap I have 
> ever
> checked reads at least a couple of micro amps.
> 
> If you have a doubt about a type of capacitor find one that you can 
> pull one
> end on. Hook up the tester and see what it reads. If it's ok then 
> solder
> that end back in. On the truly bad stuff you won't be able to find 
> one good
> one .....
> 
> Both the green and brown switch wafers will soak up de-oxit. The 
> brown ones
> swell up a bit more, but they both retain the stuff. In either case 
> it's
> probably not a  good thing, but nether are dirty contacts.
> 
> One thing you might do while you have the RF deck out of the radio - 
> meg out
> the AGC line and see what it reads. I have never tried it but each 
> time I
> put a deck back in I kick my self for not thinking of it. I have no 
> idea
> what it should read, but the schematic should be fairly easy to 
> follow.
> 
>     Enjoy!
> 
>         Bob Camp
>         KB8TQ

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