Ericsson MPI-II VHF User Manual

1.

"Tin" one terminal end of the new component and the
corresponding pad of the PWB. Use as little solder
as possible.

2.

Place the component on the PWB pads, observing
proper orientation for capacitors, diodes, transistors,
etc.

3.

Simultaneously touch the "tinned" terminal end and
the "tinned" pad with the soldering iron. Slightly
press the component down on the board as the solder
liquifies. Solder all terminals, allowing the compo-
nent time to cool between each application of heat.
Do not apply heat for an excessive length of time and
do not use excessive solder.

With a hot-air system, apply hot air until all
"tinned" areas are melted and the component is
seated in place. It may be necessary to slightly press
the component down on the board. Touch-up the
soldered connections with a standard soldering iron
if needed. Do not use excessive solder.

4.

Allow the component and the board to cool and then
remove all flux from the area using alcohol or another
GE approved flux remover.

Soldering and de-soldering techniques of the surface

mounted IC’s are similar to the above outlined procedures
for the surface mounted chip components. Use extreme care
and observe static precautions when removing or replacing
the defective (or suspect) IC’s. This will prevent any damage
to the printed wire board or the surrounding circuitry.

The hot-air soldering system is the best method of

replacing surface mount IC’s. The IC’s can easily be re-
moved and installed using the hot-air system. See the manu-
facturers instructions for complete details on tip selection
and other operating instructions unique to your system.

If a hot-air system is not available, the service technician

may wish to clip the pins near the body of the defective IC
and remove it. The pins can then be removed from the PWB
with a standard soldering iron and tweezers, and the new IC
installed following the Surface Mount Component Replace-
ment procedures. It may not be necessary to "tin" all (or any)
of the IC pins before the installation process.

 The modules, all of which are located on the Synthe-

sizer Board, are very reliable devices. Before replacing any
of the modules, check the associated circuitry thoroughly to
insure there is not a problem elsewhere. If replacement is
necessary, follow the below procedures.

All of the component lead holes on the Synthesizer

Board for the modules are plated through from the top to the
bottom of the board. This allows for easy removal and
replacement of the modules as long as appropriate soldering
techniques are observed. Always observe static precautions
when handling the board during module replacement.

To remove a module, position the Synthesizer Board in

a work vice (face down, chip components up) and remove
the solder from the plated-through points at the appropriate
pins. If a hot-air system is employed, use an appropriate tip
that will localize the heat on the pins and not on surrounding
chip components. Solderwick

®

 or a vacuum de-soldering

iron will also remove the solder if a hot-air station is not
available. When all solder has been removed or liquefied,
the module should drop out of the eggcrate casting.

To install a module, clean any solder from the plated

through holes and clean all flux from the board. Next, install
the replacement module making sure that all pins align in the
proper holes on the Synthesizer Board. Resolder the pins to
the board. Clean the flux from the board using an approved
solvent and clip any excess lead length.

As preventative maintenance to insure that the radio is

always operable, regularly schedule the following checks to
be made on each radio.

1.

Check the condition of and clean electrical connec-
tions such as antenna, battery and battery charging
contacts.

2.

Check RF power output.

3.

Check the transmit frequency.

4.

Check the transmit modulation.

5.

Check the receiver sensitivity.

6.

Check receiver audio.

7.

If not using speaker/microphone, be sure the Accessory
Jack Cover is securely in place.

The MPI-II radio uses a Nickel Cadmium battery. Two

watt radios use a 7.5 volt battery (19D900639G6) and four watt
radios use a 10 volt battery (19D900639G7). The batteries are
sealed at the factory and are not serviceable other than regular
cleaning of the contacts. Table 3 below provides the current
consumption for different operating conditions.

Nickel-Cadmium batteries in some applications can de-

velop a condition of reduced capacity, sometimes called
"Memory Effect". This cndition may occur when:

1.

The battery is continuously overcharged for long peri-
ods of time.

2.

A regularly performed duty cycle allows the battery to
expend only a limited portion of its capacity.

If the nickel-cadmium battery is only sparingly or seldom

used and is left on continuous charge for one or two months at
a time, it could experience reduced capacity. This would sev-
erly reduce the life of the battery between charges. On the first
discharging cycle, the output voltage could be sufficiently
lowered to reduce the battery’s hours of useful service.

The most common method of causing this limited capacity

is regularly performing short duty cycles; when the battery is
operated so that only a portion (50%) of its capacity is ex-
pended. This type of operation can cause the battery to become
temporarily inactive and show a severe decrease in the ability
to deliver at full rated capacity.

Any nickel-cadmium battery showng signs of reduced

capacity, should be carefully checked before being returned
under warranty or scrapped. If reduced capacity is suspected,
the following procedure may restore capacity:

1.

Discharge the multicell battery at the normal discharge
rate until the output voltage is approximately 1 volt per
cell. For MPI-II radio batteries this equals 6 volts output
for 2 watt radios and 8 volts output for 4 watt radio.

Refer to the typical Ni-Cad cell discharge curve in
Figure 9. Note the flatness of the discharge voltage.
Discharging below the kene of the curve does not give
added service. Experience shows that discharging be-
low 1.0 Volt is not necessary for reconditioning a cell.

Some chemicals may damage the internal and ex-
ternal plastic parts of the MPI-II unit.

Receiver

36 mA

36 mA

Standby

Receiver

200 mA

200 mA

Full Audio

Transmit

750 mA

1050 mA

Table 3 - Battery Drain

Figure 10 - Alternate IF Option

Figure 9 - Typical Ni-Cad Cell Discharge Curve