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
(704) 837-9200
Also. . . . credits from the various posters. . .
Tape Mods:
+------------------------------+--------------------------------------------+
| Jeff DePolo - N3HBZ | Via the Net: depolo@eniac.seas.upenn.edu |
| University of Pennsylvania | Electromagnetic: 147.225/224.980 in Denver |
| Computer Science Engineering | The Old Fashioned Way: (303) 469-1078 home |
| Class of 1991 | (303) 469-7765 work |
+------------------------------+--------------------------------------------+
Carrier Detection Light:
Bob Parnass AJ9S, AT&T Bell Laboratories - att!ihuxz!parnass - (312)979-5414
Other Mods:
Frank W9MKV @ K9IU reid@gold.bacs.indiana.edu
{inuxc,rutgers,uunet!uiucdcs,pur-ee}!iuvax!silver!commgrp
"Hams across the water, hams across the sky."
brandt@bnrmtv.UUCP (Adrian Brandt)
ewb@raybed2.UUCP (EUGENE BALINSKI)
| Tom Link, University of Pittsburgh Computer Science
| BITNET: chain@pittunx
| USENET: ...!pitt!cisunx!chain
| ARPANET: chain%unix.cis.pittsburgh.edu@vb.cc.cmu.edu
| CC-NET: chain::cisunx
| UUCP: {decwrl!allegra,bellcore,cadre,psuvax1}!pitt!cisunx!tjw
| AT&T: 1 (412) 731-6296
| US-MAIL : 310 Surrey Place, Pittsburgh PA 15235-5056, USA
Steve Meyer, N6QGG
Student, UC Davis
Internet: smmeyer@ucdavis.edu
Bitnet: smmeyer@ucdavis.BITNET
UUCP: {ucbvax, lll-crg}!ucdavis!smmeyer
Packet: n6qgg @ kg6xx-1
Harry Burford - NCR E & M Wichita, Printer Engineering
PHONE: 316-636-8016 Amateur Call: KA0TTY
FAX: 316-636-8889
C-Serve: 76367,151 Harry.Burford@Wichita.NCR.COM
\ / C r o s s r o a d s C o m m u n i c a t i o n s
/\ (602) 941-2005 300|1200 Baud 24 hrs/day
/ \ hplabs!hp-sdd!crash!xroads!coffin
MBramwel@business.uwo.CA (Mark Bramwell 519 661-3714)
And, of course, your gracious compiler . . .
--
*-> Mark A. Holtz <-> AppleLink PE: Mark Holtz <-*
*-> 7943 Sungarden Drive <-> GEnie: M.HOLTZ <-*
*-> Citrus Heights, CA 95610-3133 <-> Phone: (916) 722-8522 <-*
*-> UUCP: ...!pacbell!sactoh0!mholtz <-> RESERVED PARKING SPACE!! <-*