From: kevin.jessup <kevin.jessup@mixcom.mixcom.com>
Subject: BC200xlt battery mod: not required??
Organization: Milwaukee Internet Xchange BBS, Milwaukee, WI U.S.A.
Distribution: usa
Date: Fri, 08 Jan 1993 01:57:06 GMT

I recently found this battery mod for the Uniden BC200xlt scanner on a
ham radio BBS.  I'm sure many here have already seen it, but I am posting
it again because I've had problems with it!  First, the mod instructions
(again) and afterwards, my problems...


   *****************************************************
   ALL USERS OF THE BEARCAT 200-XLT HANDHELD SCANNER HAVE PROBABLY HAD
   PROBLEMS CONCERNING SHORT BATTERY PACK LIFE.  BATTERY INDICATOR COMES
   ON TOO SOON.  AFTER TINKERING AROUND WITH THE RIG, A SIMPLE SOLUTION 
   HAS BEEN FOUND.  THIS MOD WILL VOID YOUR WARRANTY AND YOU DO THIS AT
   YOUR OWN RISK.  [I HAD NO PROBLEMS WHATSOEVER.]

   1.  SLIDE OFF BATTERY PACK.
   2.  REMOVE TWO SCREWS ON BACK OF RIG.
   3.  REMOVE TWO SCREWS ON BOTTOM OF RIG THAT HOLD CLIP IN PLACE.
   4.  CAREFULLY REMOVE BACK OF SCANNER.
   5.  REMOVE TWO SCREWS AT BOTTOM OF BOARD NEAR RED CONTACT WIRE. L+R
   6.  SEPERATE THE TWO BOARDS VERY CAREFULLY.  CONNECTED BY 16 PIN DIP SOCKET.
   7.  BOARD IS PH-069AA  OR PH-O69AC.  POSITION BOARD WITH DIP SOCKET AT LOWER
       RIGHT HAND SIDE.
   8.  AT LOWER LEFT OF BOARD, NOTICE TWO ELECTROLYTIC CAPS.  C-214 C216.
   9.  D-203 IS LOCATED JUST ABOVE THESE TWO CAPS.  IT IS A GLASS TYPE ZENER
       DIODE WITH COLORED BANDS FOR MARKINGS.
  10. WITH A SMALL, FINE PIECE OF WIRE SOLDER ACROSS DIODE D-203.
  11. THAT'S IT!!!!!!  NOW THE BATTERY INDICATOR WILL NOT COME ON AND YOU WILL
  NOT BE BOTHERED BY TURNING OFF AND ON THE RIG TO RESET THE TIMER.  [THUS
  ENABLING YOU TO USE THE NICAD PACK TO IT'S FULLEST EXTENT.]  DISPLAY
  BLANKS OUT AT ABOUT 4.5 VOLTS.
  12. RE-ASSEMBLE RIG IN REVERSE ORDER AND YOUR IN BACK IN BUSINESS.

  MARK MACHCINSKI
  3357-14TH STREET
  WYANDOTTE, MI  48192-6120

  MARK N8JCF @ WA8OOH
  ************************************************


Well, that was simple enough to do (and un-do).

But...it made no difference that I could tell and I am certain I shorted
out the correct zener diode.  (I have the 200xlt service manual and I
used to work as an electronics tech.)

So here's the problem...

Just before doing the mod, I let the scanner run till the flashing low
battery indicator came on.  I then let it continue to run till the CPU
shut the unit down.

I immediately removed the battery and performed the mod.  (It took only
5 minutes).  I reassembled the unit and attached the battery.

As expected, the unit turned on and there was no low battery indicator.
Unfortunately (and to my surprise) the unit ran only 3 more minutes till
the audio output became so scratchy sounding that it was unreadable.  This
was at a low volume setting too.

It seems to me that the diode mod was not needed and that, in fact, the
zener diode used in the unit  was at a proper voltage for correct low
battery detection.  The unit and the battery are in near-new condition.
The unit's date of manufacture code indicates that it was made in July
of 1992.

Could it be that Uniden has corrected the problem (an improper zener
diode, or associated comparator circuitry) with the newer units??

BTW, the Uniden service manual does not list the zener's voltage but
does give a number: HZK3CLL01-TR.  The schematic DOES list test points
at either end on the zener.  These voltages are shown as 7.8 (at the
cathode) and 4.5 (at the anode).  This gives a zener voltage of 3.3V.
Can anyone confirm these numbers on older versions of the service
manual?

-- 
Kevin Jessup, kevin.jessup@mixcom.mixcom.com

        "Friends don't let friends run DOS."
                          -- Microware
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