[R-390] It _WORKS_!

[Bob Camp]

Hi

The magic of tubes strikes again. I have chased this sort of thing on a 
"goes out every month" basis on a couple of radios. Here's what I 
finally started doing:

Find a piece of wire or a tool that's roughly the size of a tube pin. A 
quick pop in and out on each of the tube socket contacts will give you 
a fast idea if any of the contacts are loose. One neat thing to use is 
an old soldering tool that looks sort of like a straight dental pick. 
They threw me out of Weapons Spec. soldering school before they got to 
that part of the course so I never did find out what you really use 
that thing for or what it's called.  I ground down the end of the gizmo 
so the body is about tube pin diameter.

Sometimes the darn sockets just seem to give up. Depending on the 
construction you may be able to bend them back to life, you may be able 
to pop them out of the socket (rare) and replace them, or you may have 
to replace the socket.

	Take Care!

		Bob Camp
		KB8TQ



On Jul 7, 2004, at 1:16 PM, mikea wrote:

> Last night I finally had the time, inclination, clear workspace, and
> tools to try to get my R-390 (Collins, great restoration by Mish) up
> again. It had Just Stopped Working a few months back, and things were
> not conducive to my getting into it until now.
>
> Symptoms:	No audio out, no carrier level meter deflection on
> 			any band, even with a signal generator as input.
>
> So I got the -20 and -35 manuals out, heated up the scope and 8640B,
> opened the critter up, and ran through the problem determination
> checklist:
>
> o	no response to any signal on the antenna connector;
> o	good response to 455 KHz modulated with 1 KHz on the
> 	IF strip input jacks;
> o	OK response to RF on the test point at the output end of the
> 	RF module, but not at the other end.
>
> Conclusion: Probably something in the RF module.
>
> Found the tube extenders (a battle all in itself, after I cleaned up
> the garage), pulled the middle tube, put it on the extender, and ...
> the radio worked! Left _EVERYTHING_ else just as it had been, replaced
> the tube, and it _still_ worked.
>
> I spent the rest of the evening cruising around, listening to hams,
> refining my SSB tuning technique, and having a good time.
>
> It probably was oxidation on one or more of the socket contacts and/
> or the tube pins. That's my story, anyway, until it quits again. It's
> easier to shoot a solid bug than an intermittent one.
>
> -- 
> Mike Andrews
> mikea at mikea.ath.cx
> Tired old sysadmin
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