Installing The PIEXX Board In The ICOM IC 745
The ICOM IC 745 at WA2FNQ
In the 1980's, ICOM made a series of radios in which the memory functions and the characteristics of the radio
were stored in DRAM (Dynamic Random Access Memory). These radios were the R71, IC 745, IC 751, IC 751A, IC 271, IC 471 and IC 1271A.
DRAM is a volatile memory and uses a lithium back up battery to retain its information. The problem is the lithium battery can be
expected to last 5 to 7 years, maybe 10 years at best. When the battery goes dead the radio not only looses its memory channels but
all the information which made the radio work. In other words, when the battery dies the radio becomes an expensive paperweight. The
solution to this problem is to replace the DRAM board with one made by PIEXX, WILLCO or Roberto Nardo, IK2RND. All these boards
have the radio information stored in non volatile memory.
I inherited my ICOM IC 745 from my dad. He had bought it from another Ham I was friends with so I was familiar with the radios history.
I knew that in 25+ years neither the battery or DRAM board had been replaced. I was really working on borrowed time.
I went with the PIEXX board because it was immediatly available and was at my house almost overnight. That gave me comfort in knowing
I had something to fall back on should the battery finally go dead. The down side of the PIEXX board is that it still uses a common
CR2032 battery to hold up only the memory channels. This is not a big deal for me because I don't extensivly use the memory channels.
Re programming 3 or 4 memories every few years is not an issue.
This web page is not instructions on how to install the new board. Please follow the directions that come with the board carefully.
This is just some of my observations which I hope will be useful.
Both sides of the PIEXX board.
As shipped, the PIEXX board came jumpered for the IC 751. It had to be re - jumpered for the IC 745. The solder was
removed from jumper pads JP 2. The tip of a fine jewlers screwdriver was run between the pads to make sure there was no solder bridging
the pads. Then solder was applied to jumper pads JP 1. See photos below.
Left - The board as shipped jumpered for the IC 751.
Right - The board re - jumpered for the IC 745.
You can get to the DRAM board by removing the bottom of the radio. There are six screws on the bottom and three screws
on each side. You'll find the board on what's normally the right hand side of the radio. Photos below show the original ICOM board and the
board as found in the radio.
Left - The original ICOM DRAM board.
Right - The DRAM board installed in the radio.
To remove the board from the radio unscrew the mounting screw in the corner and carefully pull the board out. The board
sits on 2 headers on the main board. Be careful not to bend the header pins.
The radio with the DRAM board removed.
I found it easier to work if the regulator assembly was removed. It's held in place with three screws. To get to the
third screw it's necessary to remove the top cover. It's held in place by six screws. The speaker will also need to be disconnected. Note
where the speaker is plugged in when removing the top cover.
Left - The PIEXX board installed in the radio.
Right - View with the regulator board removed.
Lastly, make sure you align the pins correctly otherwise the radio will do very strange things. Double check because even
though the board may look like it's installed properly it may not be. You will not be able to use the original board mounting screw. It's way
too small. You can try to find something that works but unless you intend to subject the radio to a lot of vibration you'll be OK without it.
All pictures taken with the Sony MYLO COMM 2