Subject: Don't junk that old Bearcat BC-300 scanner
Newsgroups: rec.ham-radio

x
              DON'T JUNK THAT OLD BEARCAT BC-300
                     by Bob Parnass, AJ9S

   Although the Bearcat BC-300 scanner is no  longer  available, it
   occupies a fond place in my collection.  I exercise little self
   control when I see  a  used  BC-300  for sale cheap, and have
   adopted two broken units.  They make fine radios after repair.

   The BC-300 was the forerunner of today's 760XLT.  It  was a  50
   channel  feature  laden scanner, introduced around 1979, back when
   Bearcat  was  part  of  Electra.   Retail sales  of  the  BC-300
   continued until 1987, when it was discontinued by Uniden.

   Although Electra offered the  pricey  BC-350  as  a  step above  the
   BC-300, firmware bugs and a batch of bad power transformers doomed
   the 350, and  the  300  remained  the jewel of Bearcat line.

   It's easy to see why the BC-300  model  was  offered  for several
   years.  It boasted premium features like a clock, a carrier operated
   solid state relay  for  tape  recorder activation,  a transmission
   counter, and a Service Search of 11 ROM banks of preprogrammed
   channels.   For  memory, the BC-300 used EAROM (electronically
   alterable read only memory), so backup batteries were not
   necessary.  The Dog House,  a  radio  shop  in Fairfax, Virginia, at
   one time offered the DH 1000, a 1,000 channel adapter for the  BC-
   300!   Unfortunately  for federal band listeners, the BC- 300 lacked
   coverage of the 138-144 and 406-420 MHz bands.

   While outwardly  impressive,  internal  construction  was typical
   of  Electra  hand  wiring  in  that era -- a bit messy.  BC-300
   schematics show at  least  100  components changed  between
   earliest  and later units.  The scanner went through many circuit
   design changes, but rather than changing  the  printed circuit
   board, new components were tack soldered on the foil side in
   different positions.

   Electra stamped all of its scanners with a  manufacturing date
   code  on  the  rear  of  the  cabinet.  The code is comprised of a
   single character (C = Cumberland, Indiana, P  =  Puerto Rico),
   followed by four digits denoting year and week the  radio  was
   built.   For  example,  "P2284" denotes  the  radio  was  made in
   the Puerto Rico factory during the 22nd week of 1984.

   Switching power supply failure was common in early  units due  to
   insufficient  capacitance.  Electra responded by increasing the
   value of capacitor C98 from 22 ufd/16 v to 47  ufd/25  v,  but  I
   recommend  47  ufd/35 v.  If your display is getting abnormally dim,
   C98  is  probably  the culprit, as it was in five Bearcat scanners I
   fixed.

   Squelch preset potentiometer R81, mounted  on  the  radio circuit
   board,  was  misadjusted in new units, requiring readjustment after
   the components aged.

   In one radio, I replaced Q9, a small signal PNP  transis- tor.  Its
   failure caused the BC-300 to become deaf on all but the UHF band.
   Failure of squelch gate transistor Q15 caused the squelch to remain
   open at all times.

   Cold solder joints, especially on the  wires  and  ribbon cable
   connecting the radio board to the logic board, have been responsible
   for other failures.

   I have seen serious IC failures in  three  BC-300s  built around
   1984.   These include CPU chip IC201, memory chip IC202, and IC203,
   not in stock at your your  local  Radio Shack.

   The BC-300 circuitry, especially on the radio  board,  is very
   similar  to  the  circuitry  in the the BC-220, BC- 20/20, BC210XL,
   and  BC-350,  so  some  of  the  previous remarks may be applicable
   to these models as well.

   I can neither furnish schematics nor repair  your  radio.  If  you
   come  across a broken BC-300, obtain a schematic from Uniden and
   spend some time troubleshooting.  If  you give  up,  your  BC-300
   can be fixed by Electronic Repair Centers in Franklin Park,
   Illinois,  (312)455-5105.   I'm told  they do good work.  The BC-300
   is a classic scanner and worthy of your efforts.

-- 
Bob Parnass AJ9S,  AT&T Bell Laboratories