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Repair Tips for Radio Shack Scanner Radios


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           REPAIR TIPS: RADIO SHACK SCANNER RADIOS

         Copyright 1997 - 2001 by Bob Parnass, AJ9S

  [NOTE: This article may not be reproduced in whole or in
 part on CDROMS, in bulletin boards, networks, or
 publications which charge for service without permission of
 the author.  It is posted twice monthly on the USENET
 groups rec.radio.scanner, alt.radio.scanner,
 sci.electronics.repair, and rec.radio.info.  It is also
 available electronically from the rec.radio.scanner ftp
 archive on the official USENET FAQ library
 ftp://rtfm.mit.edu/pub/usenet-by-group/.
 The author writes a monthly "Scanner Equipment" column for
 Monitoring Times magazine, published by Grove Enterprises,
 http://www.grove-ent.com but views expressed in this
 article are his own.]

                        Introduction

 Radio Shack has been selling scanners and monitor receivers
 under the Realistic and Radio Shack labels for over 30
 years.  Most of them were manufactured by General Research
 Electronics of Tokyo, though many newer models are
 manufactured by Uniden.

 The date of manufacture is usually printed on a gummed
 label on the scanner as well as the cardboard box.  A code
 of 12A5, means the scanner was made in the 12th month of
 1975, 1985, or 1995, for example.

 There's another way to date Radio Shack scanners
 manufactured by Uniden.  The first digit of the long serial
 number is usually the last digit of the year of
 manufacture.

 Another way to roughly estimate a radio's age is to examine
 the 4 digit date codes often stamped on the integrated
 circuits.  The radio must have been made after the most
 recent date stamp.

      Schematics, Owner's Manuals, and Parts Available

 I cannot furnish schematics, manuals or parts.  Service
 manuals for most Radio Shack scanners sold through mid-1997
 may be ordered through your local Radio Shack store.

 If Radio Shack doesn't have a schematic, try obtaining a
 Photophacts from Howard Sams Publishing division of
 Prentice-Hall at (800)428-7267, http://www.samswebsite.com

 Parts lists for recent and many older models are available
 on line at: http://support.tandy.com.  Parts may be ordered
 through Tandy National Parts, telephone (800)241-8742, or
 through your local Radio Shack store.  You may be able to
 obtain some technical assistance from Tandy by calling
 (800)843-7422, option 2.  The RSU (Radio Shack Unlimited)
 phone number is (800)-433-2024.  Grove Enterprises
 http://www.grove-ent.com occasionally sells manuals, too.

 G & G Communications (telephone (716)768-8151) is a family
 owned company which repairs scanners and stocks parts for
 several older models, especially Electra/Bearcat and
 Regency brands, but they don't sell manuals or schematics.
 They are located at 7825 Black Street Rd., LeRoy, NY 14482.
 (http://www.iinc.com/ggcomm/ or email ggcomm@iinc.com or
 ggcomm@aol.com)

            GRE-Built Base Models: Dim Backlight

 The backlight in many base models, including the PRO-2022,
 PRO-2004, and PRO-2005/6 is implemented by an
 electroluminescent panel, which grows dim with use.

 The EL panel used in the PRO-2005 and PRO-2006 is
 designated EL-501, and is identified by Radio Shack part
 #10800050.  A new EL panel can be ordered through your
 Tandy National parts (see above) or local Radio Shack store
 and sent to your home.  Radio Shack no longer sells
 replacement EL panels for the PRO-2004, but Robert Cummings
 has modified an LCD from a Miller Engineering
 (http://www.microstru.com) experimenter's kit and fitted it
 to his PRO-2004.  See
 http://home.cfl.rr.com/scan/Backlight.html for details.

 Replacing the backlight is an operation which requires care
 and patience.  Purchase a service manual, and study the
 exploded parts diagrams as you read the following steps.

 Top and bottom cabinet pieces must be removed, then the
 speaker unplugged from the main board.  The front panel
 assembly must be removed from the chassis by removing 4
 flat head screws, 2 on each side.  You need not disconnect
 all the wiring harnesses, though you might have to unplug
 one so it won't get in the way of a hot soldering iron.

 Unsolder the bare ground wire soldered to a large shield on
 the back of the front panel, located near the back of the
 squelch control.  Two ground braids must be temporarily
 disconnected by removing the screws which fasten them to
 the chassis.  After removing the volume and squelch knobs,
 you must remove 8 small screws which fasten the plastic
 front panel to the diplay board.

 The old EL panel is fastened by a bead of glue and two foil
 type leads soldered to the display board.  It's easier to
 cut the two leads from the old EL panel before unsoldering.
 A sharp knife should be used cut away the glue.  The old EL
 panel can then be slid gently out from behind the LCD
 display.

 The new EL panel can be installed by reversing the process,
 though I found that it is not necessary to glue the new
 panel.  The two foil leads must be soldered using a minimum
 of heat.  Reassemble the pieces in reverse order of
 disassembly.

            GRE-Built Portables: Worn Out Keypads

 The keypad on late model GRE-made Radio Shack portables,
 e.g., PRO-39 and PRO-43, can become unreliable after
 prolonged use.  The best repair is to replace the rubber
 keypad instead of trying to restore contacts using
 chemicals.  A replacement rubber keypad (PRO-43 keypad is
 RSU#10789808) may be ordered inexpensively through Tandy
 National Parts or your local Radio Shack Store.

                    PRO-43: Loss of Audio

 Early PRO-43s were built with a 200 mW speaker (mfr's part
 #EAS-3P123A).  The voice coils in some of these speakers
 have opened, resulting in lack of audio output, though
 audio is still available from the earphone jack.  A more
 capable 500 mW speaker is available through Tandy as
 replacement (EAS-3P127).

                       PRO-43: Freezup

 If you attempt to lock out all 20 channels in a memory
 bank, then scan only that bank, your PRO-43 will freeze up
 and be placed into a catatonic state.  Use the procedure
 documented in the PRO-43 user manual to fully reset the
 scanner.  This will "break the trance," but all the memory
 channels will be cleared.

                       PRO-2004: Dead

 If your PRO-2004 is completely dead, check R235, a 1 ohm, 1
 watt resistor mounted vertically on the main board.

            PRO-7A: Channels 1 - 4 or 5 - 8 Dead

 If the first or last 4 channels in your 8 channel PRO-7A
 crystal scanner are not working and the lamps for those
 channels won't light, replace IC4 or IC5 (type 7400A).

-- 
==============================================================================
Bob Parnass, AJ9S                                        parnass@bell-labs.com

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