Hacker Chronicles 2/HACKER2.BIN/875.PR2004.MOD

Text File | 1989-08-07 | 12KB | 260 lines

Welcome, welcome all to the

                   Complete Radio Shack Pro-2004 Mods file
                   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                   Compiled from postings on rec.ham-radio
                         and other sources available

Some brief notes before we start. . . .

In response to numerous inquiries I am  posting a overview of the mods to  the
Radio Shack PRO-2004 scanner.  First, all mods  are done at  your own risk.  I
assume no responsibility. I do not know what effect they (the mods) will  have
on any warranty, however I would think they would probably void it. Also,  one
of the mods restores coverage of the cellular phone frequencies. It is ILLEGAL
TO LISTEN TO CONVERSATIONS IN THIS BAND!

A> Read the following statement 1,000 times over

First treat the radio as if it were CMOS, that is make sure you and it have no
built up static charges. UNPLUG THE RADIO  FROM THE AC OR DC POWER SOURCE  AND
ANTENNA!!!!!!!! Be sure to handle  the sub-assembly board and cable  connector
CN-501 with TLC, since even the slightest  damage or minor crack in the  board
will result in a scanner good for use as a boat anchor.

B> Before doing anything else . . .

Take the radio out of the case by removing the 4 screws on the back. Carefully
invert the radio.

C> Lets wrangle with a few diodes

Locate a  box-like sub-circuit.  It's near  the switch  marked "restart".  The
sub-circuit should be marked  PC-3. Carefully pry off  the cover of the  metal
box. Inside there will be a 64 pin  dip IC. This is the radio CPU. Be  careful
not to touch or short out any leads on the chip.

The following diodes will determine how your scanner will work.

D-510 in circuit - scanner will have 400 memories (10 x 40)
      removed    - scanner will have 300 memories (10 x 30)

D-512 in circuit - it will step 30kHz from 825-844.995 and 870-889.995
      removed    - it will step 12.5kHz from 825-844.995 and 870-889.995

D-513 in circuit - will not scan 825-844.995 MHz or 870-889.995 MHz
      removed    - will scan all of 800 MHz band

D-514 in circuit - scanning rate increases to 20 channels per second
      removed    - scanning rate in 16 ch/sec (alt 8 ch/sec)

!!!! WATCH POLARITY !!!! If you cannot find a location, count backwards from a
known location.

D> Turbo Scan-Another way

Turbo scan for the 2004??? Yes!! Someone has realized that if you replace  the
present 7.37 MHz ceramic resonator CX501, with a 10.7 MHz ceramic resonator it
really boosts the scan/search speed! The present resonator is soldered between
pins 29 and 30  of the CPU (IC-503).  Rumor has it that  a 10.00 MHz  computer
xtal will work just fine.

Jacque (KA9FJS) confirms that the mod  works with an ordinary 10 MHz  computer
crystal ($1  at  hamfest)  but reports  a  possibly-undesirable  side  effect:
Increasing the clock rate _decreases_ the resume-scan delay time. Jacque says:
"The manual says delay is 2 seconds; with mod, delay is <1 second. Painful  if

a channel is filled with slow responders." He reports no detection problems at
the increased scan rate.

E> The Squelch Mod

Now, locate a sub-circuit  box under the sloping  front panel. It should  have
many alignment holes in the top. Pry the cover off very carefully. Locate IC-2
in the left side of the pc board. It should be marked IC-10420. Locate  R-148,
a 47 K ohm resistor between pins 12  and 13. Cut a lead of this resistor,  But
be sure to leave enough lead on both sides of the cut to solder to. Patch in a
100K ohm resistor. Make sure there are no solder balls or short circuits.  Now
your squelch will operate more smoothly.

F> The S-meter mod that doesn't work

1 - Locate transistor Q-9 (far front  right area of the radio, just under  the
sloaping front panel.

2 - Drill a 1/4" hole in the rear chassis of the radio.

3 - Install a RCA jack in this hole.

4 - Install on lead  of a .10-uF ceramic disc  capacitor to the center lug  of
the RCA jack and the other lead to ground lug of the RCA jack

5 - Clip off all but 1/4" of  leads of a 10-K ohm resistor. Carefully,  solder
one lead to the collector (center lead) of Q-9. PRETIN ALL LEADS AND USE A LOW
WATT IRON WITH SHARP TIP!!!

6 - Solder a 12" wire to the free end of the 10-K resistor. Slip a 1"  section
of insulated tubing over resistor and wire to prevent shorting.

7 - Connect free end of the wire to the center lug of the RCA jack.

8 - Connect a voltmeter capable of reading between 1 and 3 volts, DC  (digital
or analog to  a RCA plug.  Red wire to  center, and black  wire to the  shell.
Shielding in not needed.

Connecting the  RCA jack  and plug  will now  give you  a measurement  of  the
receivers intermediate frequency  automatic gain control  (IF AGC) the  author
said the range will be between +1.87 volts DC with no signals present to  +2.6
volts DC for a strong signal. He also suggested that a digital voltmeter  with
2 or three decimal places gave better resolution.

Brace yourself for disappointment -  the integrated circuit mentioned for  the
S-Meter modifaction  is used  for WBFM  only. Despite  the internal  IC  block
diagram in the service manual, pin 10  on my PRO-2004 is useful as an  S-meter
output only when the radio is in the WBFM mode.

Between pin 10 and ground, I placed a 10,000 ohm resistor in series with a 250
microamp meter for a simple  test setup. The meter  read full scale on  strong
signals. With no signal at all, the  meter read about 70% of full scale.  When
the mode is set to AM or NBFM, the meter was always at zero.

One could add a  bridge circuit here,  but this metering  point is of  limited
utility.

G> A carrier operated light

With a room full of functioning scanners, it's difficult to determine  quickly
which radio is "talking." I use separate external speakers on each radio,  and
the spatial separation helps.

In addition to "hearing" which radio is active, I like to "see" which radio is
active, and carrier  operated lights  are effective at  providing such  visual
cues. The idea  is to illuminate  a lamp when  a signal opens  the squelch.  A
small yellow light emitting diode (LED,  another Bell Labs invention) is  well
suited to this purpose. The following modification works well on all  PRO-2004
modes.

To add a COR light  to the PRO-2004, make use  of the "scan control" pin  (pin
13) on IC2, the TK10420 IC. Pin 13  has voltage present only when a signal  is
detected. This chip contains the  IF, detector, limiter, and squelch  circuits
for NBFM.

If you tremble with an electric drill in your hands, read no further. The  LED
can be mounted in a small hole  drilled through the plastic front panel,  just
to the right of the headphone jack.

Electronically, the circuit is simple. The voltage at pin 13 is not enough  to
drive the LED directly, so a  general purpose NPN transistor (e.g., a  2N2222)
can be used as a solid state switch.

- Pin 13 of  IC2 is  connected to  the transistor  base through  a 10,000  ohm
  resistor.

- The emitter is grounded.

- The collector is connected through a 1000 ohm resistor to one end of an LED.
  This resistor limits the LED current to about 13 milliamps.

- The other end  of the LED  is connected to  one contact on  the rear of  the
  PRO-2004's on/off, volume control. This  furnishes about 14 VDC  unregulated
  to the circuit. The back of the on/off switch has two contacts. Use the  one
  with the brown wire connected to it, as this contact is only "live" when the
  scanner is turned on.

I mounted the 2 resistors and transistor on a small PC board, which I fastened
to the PRO-2004 chassis using a metal standoff.

H> A Tape Relay

This mod works on  the same principle: you  use the same pin  (13?) on the  IC
that you normally use  for the carrier  detect light, but  instead of a  light
being used, I  used a small  low-current relay. Connect  the primaries of  the
relay in place of the light. You will have to determine the proper  resistance
to wire in  series, if  necessary. Then connect  the secondaries  to the  tape
recorder's "remote" jack.  Depending on  your tape  recorder, you  may need  a
normally-open relay  or a  normally-closed.  For mine,  I  used a  very  small
normally-open relay that draws about 50 ma at 12VDC that I got from one of the
mail order houses (Jameco, I think).

By the way, I have both the relay and  the LED hooked up. I use the 2N2222  as
the solid-state switch for the circuit. I also put diodes in line coming  from
the IC to the base of the transistor as well as one coming into the  collector
of the transistor just for safety sake.

I> Finally. . . .

Make sure  you re-install  the metal  cover and  re-install the  radio in  the
case!!!!!!!!!!!!!!!!!!

J> Sources
These mods are detailed in the following articles:
a) Popular Communications-August 87, PP 18-20
b) Popular Communications-December 88
b) Monitoring Times-October 87, Page 53
c) Monitoring Times-December 87, Page 60
d) Monitoring Times-July, 88, Page 93


Addresses: Popular Communications    Monitoring Times
           76 N Broadway             140 Dog Branch Road
           Hicksville, NY. 11801     P.O. Box 98
                                     Brasstown, NC. 28902
                                     [phone]

Also. . . . credits from the various posters. . .

Tape Mods:
+------------------------------+--------------------------------------------+
|      Jeff DePolo - N3HBZ     | Via the Net: [e-mail]   |
|  University of Pennsylvania  | Electromagnetic: 147.225/224.980 in Denver |
| Computer Science Engineering | The Old Fashioned Way: [phone] home |
|        Class of 1991         |                        [phone] work |
+------------------------------+--------------------------------------------+

Carrier Detection Light:
Bob Parnass AJ9S, AT&T Bell Laboratories - att!ihuxz!parnass - [phone]

Other Mods:
Frank     W9MKV @ K9IU     [e-mail]
{inuxc,rutgers,uunet!uiucdcs,pur-ee}!iuvax!silver!commgrp
"Hams across the water, hams across the sky."

[e-mail] (Adrian Brandt)

[e-mail] (EUGENE BALINSKI)

| Tom Link, University of Pittsburgh Computer Science
| BITNET: chain@pittunx
| USENET: ...!pitt!cisunx!chain
| ARPANET: [e-mail]
| CC-NET: chain::cisunx
| UUCP: {decwrl!allegra,bellcore,cadre,psuvax1}!pitt!cisunx!tjw
| AT&T: 1 [phone]
| US-MAIL : 310 Surrey Place, Pittsburgh PA 15235-5056, USA

Steve Meyer, N6QGG
Student, UC Davis

Internet: [e-mail]
Bitnet: [e-mail]
UUCP: {ucbvax, lll-crg}!ucdavis!smmeyer
Packet: n6qgg @ kg6xx-1

Harry Burford - NCR E & M Wichita, Printer Engineering
PHONE:   [phone]                 Amateur Call:  KA0TTY
FAX:     [phone]
C-Serve: 76367,151                    [e-mail]

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And, of course, your gracious compiler . . .
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