[R-390] R-392 help

[Barry Hauser]

Mark wrote:
> This is a little off subject, but I just procured an R-392/URR from a 
> little old lady in Pasadena

<snipped>

R-392 is fair game on this list -- part of the '390 series. We even 
entertain R-388's on special occasions ;-)

> It also is powered by 28VDC without using a dynamotor or vibrator power 
> supply. This means that the B+ voltage is 28 VDC!

That's right -- we don' need no steenking dynomotors, hombre.  Actually 
that's nominal 24 volt vehicular which runs close to 28 when the engine is 
running and revving.  With a 12 volt system, it can range from 12v to max 
charging voltage of about 13.6, so double in a 24 volt system.  The tube 
filaments are 26 volts nominally.

There are two separate pins for the supply voltage - one for B+ and one for 
filament. They are usually strapped together, or the power cord might have 3 
or more leads with separate connections whereby they can be spliced together 
or not.   I've heard that some use two supplies with 24 v on the filament 
and around 30 on the B+ -- supposed to optimize performance while going easy 
on the tubes.

>
> It came advertised as working, but did not when I first hooked it up. But 
> after plenty of knob-twisting (I Looooove twisting knobs), the switches 
> cleaned themselves enough to get working.

Actually, that counts as "working" as you're expected to twist some knobs to 
work it.  A lot of my acquisitions arrive in that state.

>With one caveat. When I switch to the CAL position, the thing cals up nice. 
>Switching back, however, the receiver is almost dead for about fifteen 
>minutes, then slowly regains its sensitivity.

Hmmmm ... you need to download some manuals and study up on it.  There are 
several '392 manuals on the bama site.  The 200 KC crystal is in a plug-in 
oven. You can try pulling it and switching to see if the oven has anything 
to do with it, but I doubt it.  When you switch to Cal on the AGC switch, 
among other things, it cuts out the AGC, grounds it or whatever.  You might 
have a leaky cap or a bad tube (gassy/grid emissions, etc.) in the AGC or 
related ciruits.

 Note that I live near two strong AM
> stations that put better than 10 millivolts into the receiver. And there 
> is no loss of sensitivity when tuning across them. Also note that 
> switching to Standby, then back into Normal does not cause the problem 
> (eliminating the antenna relay).

Check out the manuals where they describe the calibrator/AGC etc.

>
> Have not started troubleshooting it yet. Anybody have any ideas? And are 
> there any other R-392 owners out there to swap knowledge with?

Many of us also have R-392's.  I'm sure someone else will pop in.  IMHO, the 
'392 is one of the more neglected, unsung units going.  The thing is, they 
tend to work on deliver -- after a fashion -- often well enough that it does 
not stimulate the usual tweaking and tinkering. Also, they're small and 
humble and can hide under a bench or at the bottom of a closet for eons.   I 
have several of them -- including one that was totally solid-stated.  More 
out of curiousity than need, I did a full alignment on one of the stock 
units (not the solid state one).  Quite an improvement -- and resulting 
performance was close to that of an R-390/R-390A.

You should check out Josh Rovero's web pages on the '392. Search under 
"rovero R-392".
>
> By the way, she is horrified that it did not work when I got it, and is 
> grateful that I am sooo… understanding about it. But it came with the 
> power connector, all the tools and tube pullers still inside, origional 
> audio output tube, and an original manual. And with the exception of more 
> than a few scuffs on the case, remarkably clean! She just.doesn’t.get.it!

Lucky fellow -- tools and tube pullers are @RARE@


> P.S. Anybody have an LS-166/U speaker with origional connector they are 
> willing to part with?

Looks like Fair doesn't have 'em anymore.  They tend to turn up on 
you-know-where from time to time.

Enjoy.

Barry



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