[R-390] R-390 restoration

[Veenstra, Lester B.]

I lean toward the use of an external 300 VDC lab supply rather than =
trying to modify the internal regulator. Keep in mind no matter what you =
do internally, you still have to get rid of the IR drop heat. Instead, =
present the regulated bus with the right voltage from an external unit =
that can be disconnected to restore to the OEM design.
       Les K1YCM CTM1

-----Original Message-----
From: Barry Hauser [mailto:barry@hausernet.com]
Sent: Thursday, August 08, 2002 9:09 PM
To: DAVID MEDLEY; r-390@mailman.qth.net
Subject: Re: [R-390] R-390 restoration


Dave wrote:
<snipped>
>The 6082 is another matter end  I would love to see a thread develop
towards replacing them with >something readily available. I think there =
have
been thoughts given to solid stateing the VR circuitry but >that would =
be a
major departure from the original and spoil the radio as an item I =
believe.

Not really Dave, not all that difficult or a major departure ...

Issue #52 of the Hollow State Newsletter has an article by Dr. Jerry
analyzing a solid stated VR circuit I stumbled upon in an R-391.  This =
had
apparently been done years ago, and it has been operating well since =
then
from what I can determine.  Among other things, we compared the =
regulation
performance over a range of AC supply voltages from 95 to 125 and the =
180 B+
was comparable to most of the stock non-A's we polled -- and was also in
spec.  Only a few components -- two transistors, one or two zeners and a =
few
other parts can replace the 6082's.  This is one partial solid state
conversion that's worthwhile in view of the declining availability of
6082's -- though some are still out there -- and the damaging heat they
generate.  So, in an odd sense, it's in the best interest of preserving =
the
non-A -- so it can continue to operate on tubes dammit. (oooops)  Also, =
I
might add, the mod is reversable.

Someone has replicated the circuit as a plug 'n play as recommended in =
the
article.  Piece of perfboard with one or two octal sockets that just =
plugs
into the spot where the two 6082's normally reside.  He's done this with
currently available solid state components. (To be reported as an update =
in
a later HSN.) The '391 this was derived from was converted some years =
ago
and has old part numbers that may not be available as such anymore.  =
This
raises another issue about solid state stuff which I will rail about in
another post.

Barry (Editor, HSN)



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