GET LONGER BATTERY LIFE FROM YOUR
REGENCY MX-4000 OR MX-4200 SCANNER
by Bob Parnass, AJ9S
The discontinued Regency MX-4000 and MX-4200 are battery
operated, 20 channel scanners manufactured in Japan by
AOR. Both scanners contain a low battery warning circuit
which disables the scanner when the battery voltage falls
below a preset level.
A freshly charged battery pack should last at least 5
hours before needing a recharge. Ron Smithberg, of
Joliet, IL, complained of getting only 2 hours use from a
set of freshly charged NiCd batteries in his MX-4200.
This article describes how we increased his usage to over
7 hours between charges.
Both MX models are powered by a pack of 4 AA sized NiCd
batteries. The battery pack is nominally 4.8 volts and
has a rated capacity of about 500 mAh. The scanner draws
about 100 mA when squelched. A good rule of thumb is
that a NiCd should be recharged when its voltage falls
below 1.0 volts per cell. Using this heuristic, the MX-
4200 battery pack should be recharged when it falls below
4.0 volts under load.
CONTINUED IN FILE MX4000.3
MX4000.3
The low battery circuit on Ron's MX-4200 was misadjusted
to shut down the scanner prematurely when the battery
voltage fell below 4.7 volts. I readjusted the low bat-
tery threshhold to 4.0 volts.
You can use the same procedure, but you will need the
following equipment:
o An adjustable, regulated DC power supply, capable of
furnishing between 3 and 5 volts at 500 mA or more.
o An accurate means of measuring voltage from the
power supply. A digital voltmeter with an accuracy
of 5% or better is preferred.
o A #1 Phillips screwdriver.
o A Small, slotted screwdriver or alignment tool.
continued in file mx4000.1
MX4000.1
The low battery sensor threshhold is controlled by a
potentiometer. Here's how to readjust the sensor to 4.0
volts:
1. Turn the scanner off.
2. Connect a digital voltmeter to a well regulated DC
power supply and adjust the supply to 5.0 volts.
3. Connect the power supply to the snap terminals on
the scanner that would normally connect to the bat-
tery pack. Be sure to observe proper polarity.
Connect the positive lead of the supply to the
female snap, and the negative lead to the male snap.
4. Turn the scanner on.
5. As you watch the scanner's LCD display, gradually
reduce the power supply voltage until the scanner's
low voltage warning begins to flash.
6. Read the digital voltmeter. If it reads between 3.9
and 4.0 volts, no further adjustment is required,
just disconnect the supply and reconnect the battery
pack.
7. Otherwise, turn off and disconnect the power supply,
and continue.
8. Turn the scanner upside down, and place its
cloth so as not to scratch the case.
9. Remove the bottom tilt foot from the scanner.
10. Remove the battery pack.
CONTINUED IN FILE MX4000.2
MX4000.2
11. Remove the 4 Phillips screws holding the case bot-
tom, then remove the case bottom.
12. Reconnect the power supply to the scanner and set it
to 4.0 volts.
13. Turn the scanner on.
14. Locate a small gray potentiometer on the printed
circuit board. The potentiometer looks something
like a gray plastic Phillips screw head. If the
scanner front panel is facing you, the pot will be
just behind the keyboard on the left side. (Don't
confuse this pot with the 3 pots along the right
edge of the board. The battery voltage sensor pot
is not near any other pot.)
15. Slowly adjust the potentiometer to the threshhold at
which the low battery indicator begins to flash.
This procedure worked with great success on an MX-4200,
and its battery life was increased from 2 to 7.5 hours.
I would like to thank Rick Meyer, WB9UFL, for finding the
potentiometer in his MX-4000, and Ron Smithberg for let-
ting me experiment with his MX-4200.
MX4200.2
13. Turn the scanner on.
14. Locate a small gray potentiometer on the printed
circuit board. The potentiometer looks something
like a gray plastic Phillips screw head. If the
scanner front panel is facing you, the pot will be
just behind the keyboard on the left side. (Don't
confuse this pot with the 3 pots along the right
edge of the board. The battery voltage sensor pot
is not near any other pot.)
15. Slowly adjust the potentiometer to the threshhold at
which the low battery indicator begins to flash.
This procedure worked with great success on an MX-4200,
and its battery life was increased from 2 to 7.5 hours.
I would like to thank Rick Meyer, WB9UFL, for finding the
potentiometer in his MX-4000, and Ron Smithberg for let-
ting me experiment with his MX-4200.
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