[R-390] R-390 restoration

[Barry Hauser]

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)