[Boatanchors] BC-9: A 96-Year-Old Veteran Wakes Up

[COURYHOUSE at aol.com]

Fantastic!  
 
Dave Kudos on  getting it in shape!
 
We have a wwI sub chaser  transceiver by western electric that used  the   
VT1 and also  the  tennis ball tubes.(VT-5s?)   Thank goodness we   bagged  
tubes  eons ago. Do not  know  which are  good and  which are not...  We 
have one  that is   also  like  new  and one that  
could  use re-varnishing pf the cabinet adn may be missing a knob  etc. > 
this oen will be   up  for trade/sale? Beware it  weights 70 lbs   in a box.
 
Interesting about some of this  stuff...  the  bad   this  unit  works on 
is ... now the broadcast band!
 
ed sharpe archvisit  for smecc
 
 
In a message dated 1/13/2017 10:43:10 P.M. US Mountain Standard Time,  
arc5 at ix.netcom.com writes:

Many  thanks to all who provided info to help with
the BC-9 revival.  There  did turn-out to be a couple 
of bad caps, which I disconnected and  bypassed
with good ones.   The RF stage plate load  resistor
had drifted up from 100K to 170K.  Paralleled  another
resistor across it which brought the value back down
to  100K.  As with most "Boatanchors," there were
problems with Hi-Z  grounds and a couple of 
ancient solder joints that had gone  "cold."

Regeneration in the RF stage is controlled by varying
the  bias to the tube.  For some reason, all the resistors
in the bias  divider including the giant wire-wound pot
were burned open.  Two  resistors were made of 
scramble-wound resistance wire on a bakelite or  
hard-rubber spool, covered with dimpled tar paper.
The paper was loose  so I removed it to look at the
windings.  The open spot was not  visible on either
and I didn't want to destroy them, so I put the  paper
back on with a drop of glue and bypassed them 
with a modern  replacement.
https://goo.gl/photos/Bofb6AZ4sGQzLbsy7

Getting at the  giant bias pot required removing the
main chassis from the front panel  assembly.
https://goo.gl/photos/7RHrGWAr9GUWtPvt8
The Almighty was  kinder than I deserve, because
the open spot was right at one of the  connection 
terminals.   
https://goo.gl/photos/LcC96UkJgJnGm8At6
Burnished the contacts,  re-tensioned
the sliding contact and it was back in business.

The  BC-9 used three Western Electric VT-1
triodes and one had to "cherry pick"  from a larger
lot to get one that would operate reliably as  the
Oscillator/Regenerative Detector.  Well, buying
three tested  VT-1s is just a little bit "pricey."
Like, oh, $2100 worth of   "pricey." 
Not this lifetime.  So workable and hopefully 
"period"  substitutes were needed.  With a small
adjustment of filament voltage,  01A tubes work 
well in Audio stages, but just don't have the 
gain to  oscillate reliably in the RF stage.
With a small adjustment downward of the  
Plate Load resistor and an adaptor (Ben Hall,
you recognize this  invaluable adaptor tool?),
a triode-connected 6AQ5  works.
https://goo.gl/photos/8Na94g3V8gSBCqX87

"First  Light:"
Time to light-up this 96-year-old radio and see
if it will  play.
Cobbled-together four DC-DC converters to 
provide 6, 40 and 120  Volts.  Bias is provided
by two 9V batteries.   DC  converters, unbypassed
and unshielded, throw a few strong spurs but  
this is just for testing.  
For the loop, used a length of  RG-8.

Since my bench is in the tin-covered barn, not
much signal  gets in there.  So loosely-coupled 
an external antenna to the  loop.  Would have 
preferred to find a shortwave station playing  
"Over There," but 80 Meter CW was plenty  cool.
https://goo.gl/photos/WLcCF1oPGc64c4Zu6

There is much left to  do- need to fabricate a real
loop, build a "clean" supply and tweek the  Plate
Load resistor to optimize while seeking a better
substitute tube  for the RF stage.  Will also eventually
clean and repaint the cabinet,  recreating the 
3rd Battalion 12th Infantry markings.  I found  
good, original paint under the case hardware and
got Sherwin Williams  to match it for me in oil-base.
WWI "Olive Drab" is a darker shade than  that
used in WWII- has more brown or yellow.

Lots more to do, but  we're "on the way."

GL OM ES 73 DE Dave  AB5S


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