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Radio Shack Pro- 43 Mods Frequently Asked Questions
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Modifying the PRO-43
Copyright 1992, 1994 by Howard Bornstein
(Last revision: October 18, 1994)
This document describes how to perform three modifications to the stock
PRO-43 Scanning Receiver. These mods will:
o Restore the base and mobile cellular bands in the 800 MHz range
o Restore the 54-88 MHz range
o Drastically reduce the volume of the PRO-43 beep sound
When you restore the cellular bands, the scanner will automatically search
at the correct 30 KHz increments while in the cellular bands. The 54 to 88
MHz coverage is primarily used for TV audio in the US (channels 2 through
6), but is used for police and other services in parts of Europe.
*******************IMPORTANT NOTICE*******************************
Due to the requirements of FCC Part 15.121 subpart A , Radio Shack has
modified the production of the PRO-43 and come out with a new model, the
PRO-43A. This model can not be modified to pick up cellular reception. The
other two mods, 54-88 Mhz restoration, and the beep delete, are still
possible on the new units.
You can determine if your PRO-43 is fully modifiable by looking at the FCC
ID number on the back plate. If it reads: AA020-300 then it is modifiable.
If the ID number ends with an RAS (i.e. AA020-300A) then the unit is not
modifiable for cellular.
Why delete the beep? When you press the keys on the PRO-43, it responds
with an audio beep to let you know that the key has been "accepted" by the
scanner. This kind of feedback is usually desired, particularly since the
keyboard of the PRO-43 doesn't provide tactile feedback. Then why kill the
beep? Because the beep volume is fixed on the PRO-43 (that is, it is not
set according to the volume control knob), and, at the same time, the
volume is not equalized between the speaker and the headphone jack. Because
of this, while the beep volume is not a problem with the speaker, when you
listen to the scanner using headphones or through an amplified system like
your car stereo, the beep has the effect of a concussion grenade!
The mod reduces the beep volume from the speaker to a very soft level (you
have to be in a quiet room to hear it) and to the headphone jack to a
comfortable level.
Some things to consider before killing the beep:
If you kill the beep, you won't get (from the speaker) the normal
indication that the batteries are very low. In the case of the PRO-43,
because it stores your channel frequencies in permanent EEPROM memory, you
won't lose anything if your batteries go dead. All that happens is you
probably won't notice for a while that the scanner is not scanning anymore.
Another positive side of killing the beep is that when you use alkaline
batteries, you may have as much as three full hours of usage after the
scanner thinks that the batteries are low. This mod keeps you from going
batty listening to that beep for those three hours.
You do lose, however, the feedback the scanner gives you when you enter an
incorrect entry. Say you are going to program in the frequency 455.675.
You enter in the 455 but don't hit the decimal point properly. If you could
hear the beep, you would notice it stop beeping after pressing the second 5
(because it thinks you are entering a channel number that is outside of its
range). Without the beep, you have to rely entirely on the LCD display to
tell that something is wrong. Not a big deal, but there are several kinds
of operations that the PRO-43 helps you with that are similar to this one.
Performing the modifications:
You should have experience soldering and should feel comfortable working
with very small parts to perform these mods.
Tools:
You will need a small Philips screwdriver, a small slotted screwdriver,
small needle-nose pliers or tweezers, a low-wattage soldering iron, and a
solder sucker or solder wick. A magnifying lens of some sort (eyeglasses or
lamp) and a high intensity lamp are highly recommended!
All the references to positions assume that you have placed the PRO-43 with
the keyboard side down and the antenna at the top.
Procedure:
1) Remove the antenna and the battery pack. Then remove the 4 black Philips
screws from the back of the case. Put these and all other screws in a
secure area.
2) Pull the back case off. The case will separate near the front of the
scanner, revealing the stacked circuit boards inside. Place the scanner
down on its face. You will encounter three circuit boards. The top board is
the one you will see looking directly down. There is a second board in the
middle, and the third board is the board that has the keyboard attached to
it. The top and second board are connected together and will move as a
unit.
3) Remove the six small screws from the top circuit board. Place these
screws in a secure place.
4) The top and middle boards are connected at the bottom left by a small
black 4-pin connector. Take your small, slotted screwdriver and use it to
carefully pry up the black connector at the bottom of the top circuit
board. A good place to pry up the board is above the metal shield on the
left, bottom edge of the board. Once you lift up the top board by freeing
this connector, you can shift the top board slightly to the left and right.
By shifting this top board to access the screws underneath, you will not
have to desolder the antenna connections.
First, shift the top board to the right so that the Philips screw on the
lower left edge of the middle circuit board is exposed. Use your small
Philips screwdriver to remove this screw. You may need to use your
needle-nose pliers to grab this screw once it's loosened.
5) Shift the top board to the left so that the screw at the lower right
edge of the middle board is visible. Use your small Philips screwdriver to
remove it. You may have to angle the screwdriver slightly to get to the
screw. The needle-nose pliers may also make it easier to remove the screw.
Store these screws with the others.
6) Once both screws are removed from the middle board, the whole unit of
the top and middle board will lift out and "fold" over to the left. In
order to lift up, you have to disconnect two connectors along the right
edge of the middle board. There is a small connector near the top right of
the board and a longer one along the middle right edge. Again, use your
slotted screwdriver to carefully pry these connectors loose.
(To delete the beep) 7) After you've folded the two boards to the left,
look at the bottom of the second board. In the upper half of the board,
nearer to the left side, you will find a small surface mounted resistor
with the number "471" on it. To defeat the beep sound, you need to remove
this resistor. Heat the connectors on each side and use the sucker or wick
to remove the solder. Even after you remove the solder, the resistor may
still stick to the board. Try using the edge of an Xacto knife to pry it up
if it sticks. Otherwise, use your tweezers to pick it up. Try not to
destroy it, since you can re-install it if you want to restore the beep.
Tape this chip to the back of a business card or something similar for safe
keeping.
8) Now look at the bottom circuit board. There are a set of five diodes
that affect how the scanner scans. They are covered by the metal RF shield.
Desolder all four tabs that hold the RF shield in place. Use your
screwdriver to put a slight upward pressure on the shield near the tab you
are heating and it will pop right out. Remember the orientation of the RF
shield so you can put it back the same way when you re-assemble the
scanner.
9) After you remove the RF shield, locate the row of diodes. The labels are
not quite lined up with the diodes themselves, so be sure you can identify
which diodes are which. In a normal US PRO-43, you will see diodes 1, 2,
and 4 installed. Diodes 3 and 5 are not present. These diodes are extremely
small so you will have to be very delicate in handling them.
(To restore cellular)
10) Remove the solder on each side of diode 4, using the solder wick or
solder sucker. With tweezers, carefully lift diode 4 off the board. These
are surface-mounted components, so the leads are not soldered into holes in
the board but are attached directly to the surface of the board. If you use
pliers, be extremely careful, because you may crush the diode. You will
still get cellular restored, but you will not be able to place the diode in
D3 to restore 54-88 MHz.
(To enable 54-88 MHz)
11) If you were able to lift the diode off intact, place it over the pads
in the space for D3. Keep its orientation the same as it was on D4.
Carefully solder the diode in place.
For your information, the diode matrix performs the following functions:
Diode 1, if removed, disables the keylock switch. If in place, enables the
keylock switch.
Diode 2, if in place, enables the 30-54 MHz range. If removed, disables
30-54 MHz.
Diode 3, if in place, enables the 54-88 MHz range. If removed, disables
54-88 MHz.
Diode 4, if removed enables the cellular bands. If in place, locks out the
cellular bands.
Diode 5, if in place, steps the cellular bands in 12.5 KHz steps. If
removed, steps in 30 KHz steps.
12) Resolder the RF shield on, being careful to replace it in its proper
orientation.
13) Take the top and middle circuit board unit and fold it back to the
right, lining up the pins for the right edge connectors.
14) Replace the screws in the middle board, again, by shifting the top
board to the left and right. You may need to seat these screws in their
holes using your needle-nose pliers or tweezers.
15) Insert the black connector at the bottom of the top board, and replace
the 6 screws in the top board.
16) Replace the back case, replace the 4 black screws, replace the battery
pack and the antenna.
To test the unit:
Enter the following key sequences:
PGM
LIMIT
870
ENTER
LIMIT
896
ENTER
Now press the up arrow. The scanner should now be able to search through
the cellular base range. It will use the proper 30 KHz steps.
Now try:
PGM
LIMIT
54
ENTER
LIMIT
88
ENTER
Again press the up arrow. The scanner should now search through this low
band range of 54-88 MHz. It will step in increments of 5 KHz.
If you performed the beep delete, you will notice that the beep sound is
very quite through the speaker and comfortable with headphones.
Note on TV audio frequencies:
The range of 54 to 88 MHz is primarily used for TV audio of channels 2
through 6 in the US. TV audio is broadcast on wide-band FM (WFM). The
PRO-43 only receives FM in narrow band FM, which means that the quality of
TV audio won't be perfect. It should, however, be very understandable,
which means that you will be able to listen to the six o'clock news (for
example) on some of these channels with no problem.
TV audio frequencies:
Channel 2 59.75 MHz
Channel 3 65.75 MHz
Channel 4 71.75 MHz
Channel 5 81.75 MHz
Channel 6 87.75 MHz
Note on cellular restoration:
There is much controversy about the 1986 ECPA legislation which made it
illegal to monitor cellular communications in the US. You should be aware
that the law makes it illegal to monitor these communication, not possess a
device that can monitor them. In other words, it is not against the law to
modify your scanner to pick up these frequencies. It is just against the
law to listen to them! Please use good judgement if you make this
modification.
Note about Radio Shack and the modifications:
I certainly cannot speak for Radio Shack, but many scanner enthusiasts have
found that making modifications such as these will not necessarily void
your warranty. While it might do so technically, it seems that, if the mods
are not related to other problems that you have with the unit, Radio Shack
may very well fix the unit under warranty and leave your mods in place!
Good luck with these modifications and drop me a note on CompuServe if you
have any questions or comments about them.
Thanks very much to Jeff Goldman, Bob Kelty, Gary Ross, Todd Handley, R.G.
Schaffrath and others who helped pioneer these mods and discover what makes
the PRO-43 tick inside.
Howard Bornstein
CS: 76174,637
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