Date: 20 Sep 88 17:01:47 GMT From: rayssd!raybed2!ewb@g.ms.uky.edu (EUGENE BALINSKI) Subject: PRO-2004 MODS To: info-hams@simtel20.army.mil 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. 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