Ham Radio 2000 #1/Ham Radio 2000.iso/ham2000/scanner/mods/pro34a

Text File | 1991-10-22 | 9.4 KB | 203 lines

REALISTIC PRO34 MODS & INFO

"NOVICE NOTES" FOR PRO-34 MODIFICATIONS

1.  Remove the 4 small phillips scres on the back of the unit

2.  Remove the batter cover and battery holder from the case.

3.  Remove the two knobs on the top of the case (Volume &  Squelch)

4.  The Case has some pressure fit points, These are at the bottom of
    the case and you need to be a bit careful in forcing the two halves
    of the case shell appart. Once you have the pressure fit points
    at the bottom released, angle up the bottom of the case until
    the battery sepperation wall is clear of the internal metal frame, and
    slide towards the top of the unit, place the back half of the shell aside.

5.  Now you will see the RF boad mounted to the metal support frame, The
    BNC (antenna) conector leads and the volume control power switch leads
    are soldered directly to the board. Carefully desolder these 4 connections.

6.  At the bottom of the RF board there is a IF Can transformer that has a small
    wire as a groundign strap soldered directly to it. Desolder this as well.

7.  There will be some wires from the volume controle knob to the PC board that
    are socketed. Remove the plug from the ~F board (needle nose pliers work)

8.  There will also be a similar wire (small sheilded ) from the squelch control
    to the RF board wich is also Socketed. Remove the plug from the RF board.
    (Again Needle Nose Pliers work good here)

9.  Remove the 4 thredded stand-offs from the RF Board (these Hold the RF board to
    the internal mettal frame and are where the screws that hold the back of the
    case on go.) Use a nut driver or Needle Nose Pliers.

10. Now there the RF board is mostly free. The only thing holding it in is the row
    of connector pins on its botom side that plug into the logic board. You will
    need to pry this board up gently. Be warned that the bottom side of the RF
    board is just chock full of Very Small surface mounted omponents. So use
    something non-metalic and smooth to do the prying with.

11. Now that you have removed the RF board, place it along with the case shell back

12. The Internal Metal support frame is now exposed. there are 3 small phillips
    screws holding the mettal frame to the bottom Logic board (actually, these
    screws go through the logic board and into the front half of the case.)
    2 of the screws are near the top, and 1 is at the bottom of the metal frame.
    remove these 3 screws.

13. There is a small socketed wire that leads from the small power pc board on the
    metal frame that goes under it and is pluged into the Logic board. Lift
    the metal frame up and remove the power plug from the PC board. Place the
    metal frame with|the rest of your parts pile.

14. You are have the component side of the  Logig board exposed now. There are
    2 small phillips screws at the bottom of the PC board (where the Battery
    compartment WAS) Remove them.

15. Once you have the the last 2 screw removed the Logic board is free. The
    speaker wires lead from the speaker to the logic board on the bottom side.
    These are soldered in but there is enough play in them to allow you to
    make the mods.

16. NOTE: The keyboard lock switch is a funky little piece of plastic with
    a sliding stainless metal contactor that is just wedged inbetween the
    front case and the logic board. Remove both the switch contacts and the
    plastic switch. (best know it now or loose them in the carpet)

17. On the component side of the PC board you will see lots of nifty surface
    mounted compone~ts, a fat little barrel capacitor (used for maintaining the
    channel freqs while you change the batteries.. and make modifications :)
    near the edge of the PC board you will see a couple of small diodes moutned
    vertically. These will be labeled on the PC board as D10 and D11, you will
    also see a place for another diaode to be soldered in but was not
    installed at the factory.. this is D9.

18. You must now move diode D11 to the place where D9 is labled. As you have
    probably noticed by now there is a tin cover over about 1/2rd of the
    PC boards solder side. The edge of the tin cover nearest the diodes has
    2 metal tabs soldered to the P board. Desolder these 2 tabs and gently
    bend the metal cover way from the soder side of the PC board. This will
    expose the board enough to let you get your soldering iron in to where
    the diode leads are.

19. Desolder the D11 diode from the bottom while pulling it away from the board
    on the top  of the board using neadle nose pliers on the LEAD only.

20. Now heat up the D9 solder pads and insert the diode (the same way it was
    oriented in the D11 location)

You Have Completed the Mods for complete 800mhz band coverage and 66-88mhz band
coverage.



*******************************************************************
Subject: Eliminating a birdie in the PRO-34 portable scanner
           by Bob Parnass, AJ9S

   Birdies are unwanted signals generated within a receiver, which
   cause the receiver to "hear itself."  Some birdies are caused by the
   unwanted product of the local  oscillator.   Another  cause  is
   a  stage, which oscillates but isn't meant to oscillate, such as a
   high gain  intermediate frequency (IF) amplifier.

   Most birdies,  especially  those  generated  by  a  local
   oscillator,  are frequency stable.  It's difficult to rid a radio of
   these birdies, and solutions  usually  involve better internal
   shielding and isolation among the stages.

   A "wandering birdie"  is  one  which  changes  frequency.  Wandering
   birdies, and birdies which appear and disappear suddenly, may be
   caused by  intermittent  ground  connections within the radio, or
   defective bypass capacitors.

   After using his Radio ShackO PRO-34 portable scanner  for a  few
   months, Ron Smithberg, a radio hobbyist in Joliet, was hampered by a
   "wandering birdie."  Ron's scanner  was hearing  itself on a few
   frequencies in the VHF-Hi range, but the birdie disappeared when he
   tilted  the  radio  or squeezed  the  case.   There had been no
   problem when the scanner was purchased initially.

   I suggested that a ground connection or a  circuit  board in  his
   PRO-34  might be loose.  The thin PRO-34 plastic case feels chintzy,
   and can flex easily by applying  just a  gentle  squeeze.  After
   prolonged use, the case motion can loosen screws which were once
   tight.

   Ron disassembled his PRO-34.  He unfastened  the  helical antenna,
   knobs,  and  rear screws, then gingerly removed the plastic case.
   After Ron tightened a Phillips screw holding  the  Logic  Board
   to the front of the case, the birdie disappeared forever!

   The operation took a steady  hand.   Although  he  didn't have  to
   remove any boards, Ron warned that accessing the offending screw was
   a challenge.  He used  a  very  small Phillips  screwdriver,
   positioned  through  a  hole in a shield partition.



***********************************************************
Restoration of Cellular Frequency Coverage on
Radio Shack PRO-34 Handheld Scanner

1.  Remove battery cover and battery, four black screws on
rear cover, and volume and squelch knobs.

2.  Remove rear cover, lifting back and up to clear controls.  Do not
remove belt clip or circuit board screws.

3.  Unplug the brown volume control connector (grn/yel/blk) and white
squelch control connector (wht/blk/red) from the linear circuit board.

4.  Unsolder the ground lead from T111 (at corner of linear circuit board
above the external power connectors).  Unsolder the two power switch leads
from the back of the volume control.  Unsolder the antenna connector center
pin and ground wires from the linear circuit board.

5.  Unscrew the four combination screws that hold the linear circuit board and
received the back cover screws. Grasp the linear board at the top and lift it
straight away from the front case, unplugging the 16-pin connector.

6.  Remove the three screws holding the metal frame assembly which held the
linear board to the front panel.  Unplug the red-black power lead and lay the
frame aside.  It is still connected to the battery contacts.

7.  Locate diodes D9 - D12 on the volume control side of the of the logic
circuit board under T1; D10 and D11 are marked.  Clip one lead of D11,
separating the gap.  This may be resoldered later if desired.

8.  Reassemble the board by reversing the disassembly procedures above.

pro34.14

Date: 4 Apr 89 14:24:01 GMT
Subject: PRO-34 Scanner Modifications

    In  the  May 1989  edition  of  Popular  Communications  is a
"Letter  to the Editor" on the Radio Shack PRO-34 Scanner.  Below
is the text of that letter.


                  PRO-34 Scanner Modification

    In regard to the information  presented (March Issue)  on the
handheld Radio Shack PRO-34 scanner,  my own observations  on the
modifications have been:

1. To restore missing 800 MHz frequencies, remove D-11.

2. To add 66 to 88 MHz  (European Coverage),  install a diode at
   D-9.

3. D-10 must remain in place for full 800 MHz coverage.

4. If a diode is added at D-13 it cuts out aero band, also seems
   to affect 800 MHz channel spacing.

5. D-12 added dosen't seem to have any affect.

6. Only D-10 and D-11 are factory installed.