ICOM IC-720/A Rotary Switch Conversion to Relays

The enclosed information was prepared by Daniel - F5IKI. He has offered to share it with the ham community and we thought placing it here would make it available to as many people as possible. The information you see can be downloaded as two individual zipped Microsoft Word files which include the text, schematic and pictures. These files are located at the end of these pages.

If you have questions you should contact Daniel. I haven't done this operation (yet) and have no information or advice on doing the job. Daniel has done a good job and the information should be pretty easily followed.

======================================================================================================

After replacement of the power transistors result a bad continuity in the rotary switch, I decided to suppress it.

The modification is made with 14 relays, and a logic control, any modification outside the filter block.

The silence is now very appreciable, any perturbations on the logic control during transmission.

Construction:

Some component are moved on the PCB logic control (see photos)

L15 is moved too.

For a short connection between filters and relays PCB, is necessary to cut some tracks on the PCB filters.

The relays used are made by Goodsky, model GS SH 212T. A lot of relays with the same size, pin assignment and resistance > 700 W can be used.

Schematic diagram

image002.gif (51427 bytes)

View of logic control

image004.jpg (51343 bytes)

In the filter block

image006.jpg (53775 bytes)

View relays 1

image008.jpg (39947 bytes)

image010.jpg (36803 bytes)

image012.jpg (44810 bytes)

image014.jpg (41654 bytes)

image002.jpg (34379 bytes)

Before mounting the logic control 1

image004.jpg (41628 bytes) 2

image006.jpg (48122 bytes)

Component placement logic control

image008.jpg (36519 bytes)

Relays

Red holes will is connected with the other side by an 8/10-mm wire.

image010.jpg (26728 bytes)

PCB

image012.jpg (42377 bytes)

image014.jpg (19444 bytes)

There are two files to download and both are large. File1 is 2.2+ Megabytes and File 2 is 1.8+ Megabytes. I hope everyone has a nice fast broadband connection or else a LOT of time.