HERE'S HOW YOU CAN DOUBLE THE MEMORY ON YOUR IC-745 The following are excerpts from the WILLCO Electronics ICM-1024 NoFail memory installation manual for the IC-745 BEFORE YOU BEGIN The following instructions may appear to be simple. They are, however, quite difficult to perform. If your not a qualified technician or if you don't have the proper tools or soldering skills, you can damage your radio. If you don't think you can perform the task, you should contact a friend that is qualified. THE IC-745 32 MEMORY MODIFICATION The following steps may require the green and white "Components Layout Sheet" and schematic that came with your Icom IC-745. You will be soldering wires directly to component leads, therefore, you will need a high quality temperature controlled soldering iron. The IC745 was the first transceiver equipped with the EX-314 memory module using logic circuitry that is similar to the Icom R71 receiver (the R71 has 32 memories and the IC745 only has 16). The 16 memories are selected using a 4 bit binary rotary switch that's connected to DB0, DB1, DB2, DB3 and Y5. The 16 switch positions generate a count from 0 to F hex and is read by the microprocessor on the logic board. The R71 receiver selects 32 memories using two 4 bit up/down counter IC's that are connected to the same data bus (5 bits from the two counters generate a count from 0 to 1F hex). On the R71 the fifth bit is connected to DB4. The IC-745 32 memory modification requires the installation of a one switch and one diode. We recommend that you use the front panel PREAMP switch because it's close to the Matrix board (If the wires that connect to the Logic board are too long, they can radiate digital noise and interfere with the receiver). The switch will be used to select a second bank of memories by addressing the fifth bit (similar to the fifth bit in the R71 counters). The bank switch instructs the microprocessor to read new locations in the RAM memory. You can always add a rear mounted switch to control the pre-amp PREPARATION Disconnect the antenna and the AC or DC line power to the radio. Perform the work in a static free work space. You can also protect the radio by grounding it to a water pipe or a ground rod. If the wiring in your home or apartment is well grounded, the mounting screw on a duplex outlet is also a good ground. Connect a jumper lead to ground with a 100k resistor in series and while doing the modifications, connect the other end of the clip lead to a metal watch band. Remove the radio's top and bottom covers and place it up-side-down on a your work table. Remove the ribbon connectors that run from the Logic board (on the main chasis) to the Matrix board on the radio's front panel. The ribbon connectors are very delicate so be carefull when you un-plug them. Remove the four front panel mounting screws (they are located on the left and right side of the chasis. Disconnect the existing wires that go to the PREAMP switch and reconnect them to an external or rear mounted toggle switch (the existing wires connect to a relay that switches the pre-amp in and out). Because they connect to the coil of the pre-amp relay, you don't have to worry about the wire length. The diagram below shows the memory switch connections to the Matrix board (it's located behind the radios front panel). THE 32 MEMORY "MOD" Connect the cathode end of a 1N914 (or equivalent) diode to J13 pin 2. Connect the anode side of the 1N914 diode to the switch. Connect the other side of the switch to J12 pin 5 or W13 on the Matrix board. Now that the modification is complete you can remount the front panel and re-connect ribbon connectors. Mount the top cover. Make sure that radio is clear from tools and bare wires. Connect the radio to a power source and hook up the antenna. Turn on the radio. It should operate normally. OPERATING INSTRUCTIONS When you first power the radio, using the pre-amp switch, you can access a new bank of 16 memories. But first you will have to store new frequencies. Press the preamp switch and lock it in the down position. Place the radio in the VFO mode and store your favorite "Ham" frequencies in the first memory. Store other frequencies in other memory locations. Place the radio in memory mode and rotate the memory switch. The frequencies that you stored should appear. Press the pre-amp switch and unlock it in the up position. The old set of frequencies (that you stored before you made the "mod") should appear. SCANNING when all 32 memories are filled, the radio will scan all 32. All other functions should operate normally. Button up" the radio and enjoy! --- Jack Albert WA9FVP (Fellow Radio Hacker) Tellabs Operations Inc. 1000 Remington Blvd Voice (708) 378-6201 Bolingbrook, IL 60440 FAX (708) 378-6721 "I'm normal, I'm normal, I'm normal"! From MTV's Liquid Television