| In the early 1980s
Icom America marketed a group of transceivers and radios that
utilized the latest state-of-the-art computer technology to
enhance the operation of the radios. This technology improvement
allowed hams to afford a reasonably priced high performance
transceiver which until then was only available on units costing
much more. Features now available to the hams included: higher
frequency stability, better frequency resolution, digital
frequency display, almost instant recall of saved frequencies
(memory channels), quick mode signal processing and built in tones
and offsets for the rapidly emerging repeater operation.
Implementation of all these
features required a CPU with associated logic circuitry. In the
early 80s, the most cost effective way to implement data
processing and memory functions was through a DRAM (Dynamic Random
Access Memory) to control the CPU. This DRAM was a volatile memory
integrated circuit which required a lithium battery to retain its
instruction set. The following receivers and transceivers had such
RAM units:
IC-271
; IC-471 ; IC-1271 ; IC-745 ; IC-751/A ; IC-R71A
The lithium batteries in these
units typically lasted about 5 to 7 years before replacement was
required. This was specifically noted in each of the Owners
Manuals for the products.
This lithium battery can be
replaced by the radio owner if care is used. The following is a
recommended procedure to accomplish this:
|
-Cautions- |
|
1) Do
not use an AC powered 3 Volt DC source, your grounded
soldering iron tip could short out the battery (+) terminal.
Use a 3 Volt battery DC source only (2 alkaline cells for
example).
2) Do not solder the
external DC wires directly to the lithium battery tab pads.
If you do so, you will not be able unsolder the battery
without having the wires drop off.
3) If by accident
you lose power to the RAM unit it must be sent to Icom
America for reprogramming.
4) Be careful not to
damage or bend the connector pins on the radio side while
removing or reinstalling the RAM card. |
|
| -Procedure- |
|
1)
Disconnect the power cable from the radio, and take the
cover off.
2) Unplug the RAM
board and remove it from the radio.
3) Temporarily
solder a 3 Volt DC battery source across the existing
battery terminals (see suggested connection points on the
circuit board pictures).
If by accident
you lose power to the RAM unit it must be sent to Icom
America for reprogramming.
4) Unsolder the old
lithium battery and replace it with a new one. (BR2325 1HC,
Icom stock number 945 03112)
5) Unsolder your
temporary 3 Volt DC source.
6) Reinstall the RAM
board into the radio. |
|
| -Pictures- |
|
There are two
versions of the Icom RAM boards. Both are identical in
operation, and they are interchangeable. The differences are
in the circuit board layouts only. Note that the black and red
wires visible on these images are the suggested way of
connecting the external DC backup voltage while the battery is
being replaced. The wires are not a part of the RAM card, and
should be removed when the battery replacement procedure is
complete. Refer to the replacement procedure
outlined above.
You can click on the small
images below to view a larger version.
RAM card
version A images:
RAM card
version B images:
 |
|
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