

Article 8822 of rec.ham-radio:
Path: philabs!linus!raybed2!ewb
>From: [email-masked] (EUGENE BALINSKI)
Newsgroups: rec.ham-radio
Subject: PRO-2004 MODS  HERE THEY ARE !!!
Keywords: AGAIN !
Message-ID: <[email-masked]>
Date: 12 Jan 89 14:34:39 GMT
Organization: Raytheon Co., Bedford, Mass.
Lines: 87

    I guess it's time to post this article again. As always do these mods
at your own risk. I assume no responsibility.  73 & good listening
                                               
                                              Gene WA1UXA

    In response to numerous inquiries I am posting a short 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 !
                         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Therefore my supplying info to you does NOT in any way constitute an invitation
to break the law. You are on your own! 

    These mods are detailed in the following articles:
a) POPULAR COMMUNICATIONS AUG 87, PP 18-20
b) MONITORING TIMES OCT 87, P 53
c) MONITORING TIMES DEC 87,P 60
I suggest strongly that you obtain the back issues and read through the letters
or articles. I also suggest you subscribe to the mags. They supply a lot of    
great info and freq lists. Now the mods.
 
1) Restoring 870 MHz coverage.
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 !!!!!!!! Take the radio out of the case by removing the 4 screws on 
the back. Carefully invert the radio. 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. Near the chip there will be a row of diodes marked D-502 to D-515.
If D-513 is present, cut one lead, separate it so they will not touch, and 
magic, 870 Mhz is restored. If D-513 is not there and you still do not have
870 coverage, then a little more work is in order. Locate the 9 pin connector
"CN-501". Carefully remove it from the sub-circuit. Unscrew the screws holding
PC-3 to the main chassis. Carefully invert the sub-circuit board (PC-3).
Locate the one lone component on that side of the board. If it is a diode,
as it should be, then cut one lead and separate them as above. Re-install the
sub-circuit with the screws on to the main chassis. Reconnect the 9 pin 
connector. Do NOT put the cover back on just yet ?!  

                     2&3)   400 CHANNEL and SPEED MOD !
       On the top of the sub-circuit board, locate the slot for D-513. Count
backwards from there until you get to the space for D-510. Install a diode
at D-510 in the same polarity as the rest of the diodes. There, you now 
have 400 channels instead of 300 ! Now install a diode at D-514 and you have 
increased the scan speed to 20 channels/sec from 16 ch/sec. Carefully re-
assemble the metal box. Make sure everything else is as it should be.
RE-invert the radio so it is right side up. 
 
                        4)  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.      
           
         Again, I STRONGLY suggest you obtain the above mentioned
magazines for more details. Addresses appear below. Please ignore any 
mis-spellings, mis grammer, etc. Good luck and good listening !!!
                                                     73
                                                 Gene WA1UXA

PS, make sure you re-install the metal cover and re-install the radio in the
case !!!!!!!!!!!!!!!!!!

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

                          Standard disclaimer applies !!!!!!!!!!!!!!!!!!!