These modifications may be illegal in some areas. Also, if you are not experienced with general electronic principles, irreversible damage may occur as a result of your inexperience. These procedures are for informational purposes only. No warrantees are expressed or implied.
[Pro-2004 Mods] [Pro-2005 Mods] [Pro-2006 Mods]
The PRO-2004 scanner can be used to receive cellular telephone conversations. Originally, the scanner was able to receive in this band, but at the last minute, it was decided to delete cellular coverage from the PRO-2004. The procedure to re-instate the cellular band is simple for anyone with a pair of cutters, and a phillips screw-driver.
1. Remove the 4 philips screws on the back of the unit that hold the case onto the chassis.
2. Slide the radio out of the case by pushing it out the front. Or, put another way, slide the case back, off the radio.
3. Once you've eased the radio out, turn it upside down with the front toward you.
4. Locate a board with "PC-3" stenciled on it in big white letters. It is
roughly in the middle of the radio near the back.
5. Gently remove this metal cover. It is held on by being press-fit over little metal dimples. A little careful prying will do the trick here.
6. Once the cover is off you should see the main CPU chip on the right, a resonator crystal (501-X I think?) in the rear right corner, and a vertical row of diodes to the left of the CPU chip. Some of diode positions will be labeled like this D-509, D-510, D-511, D-512, *D-513*, etc. I don't remember exactly which ones are labeled or not, but that's not so important right now, you should get the idea.
7. The diode D-513 is labeled (I know) and this is the beastie that disables the cellular phone frequencies and their 30KHz search step size. Snip this diode with diagonal cutters (or whatever). Make sure the snipped wire ends are not touching, and viola! You've got full 800MHz coverage on your Pro-2004.
Note: If D-513 is not there, it may be soldered to the underside of the circuit board. Also, instead of snipping, desolder and save the diode for the 400 channel and scan speed modification.
8. You may want to test it at this point. (Try entering 880 MHz or some other previously disabled 800MHz frequency, and verify that you don't get an ERROR.) Re-assemble.
400 CHANNEL and SPEED MODIFICATION
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.
THE SQUELCH MODIFICATION
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.
Popular Communications, August 1987, pgs.18-20
I suggest strongly that you obtain the back issues and read through the letters or articles to verify that I did not mis-type something important :)
There is a socket that is not marked so it will be referred to as D501.
824-851, 869-896 MHz Frequency Restoration
(1) Find the center grey wire coming from CN3 and cut it midway to disable the beep tone. You may wish to solder a resistor in series to reduce the beep volume, a trimpot to vary the volume of the beep tone, or a minature switch to choose between beep and no beep. (or)
(2) Using a pair of needle-nose pliers, CAREFULLY pry the plug from CN3, revealing a
row of pins. Locate the center pin (#8) which corresponds to the grey wire and bend it
down flat, disabling the beep circuit. Reinsert the plug. The pin may be erected again
later to restore the beep tone if desired. This completes the restoration procedure.
Reattach the cover and replace the screws.
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