Some older Yaesu or Kenwood radios use standard TTL (non-inverted). You can invert the signal by adding a 74HC04 hex inverter between the opto output and the radio jack. The schematic’s open-collector design makes this easy.
Because the schematic shows the opto-couplers are bi-directional, you can tap into the PC-side lines before the MAX232 with a logic analyzer. Install 2-pin headers on the PCB traces between IC1 and the optos. icom ct-17 schematic
In this deep-dive article, we will dissect the schematic, explain the signal flow, explore common modifications, and provide the technical details needed to understand, repair, or replicate this classic interface. Some older Yaesu or Kenwood radios use standard
The signal enters via the DB9 connector. The CT-17 uses only three pins of the RS-232 standard: , Pin 3 (TxD) , and Pin 5 (Ground) . The signal enters via the DB9 connector