I bought out Rob Sherwood's 525/535 inventory. Many, many things came along with that haul. If Islanders need a part or board for one of those rigs I may have it.
You are correct. In addition to the Tune command, the AH- series random wire tuners use a serial data interface between rig and tuner to set the band/memories. As do their JRC equivalents.I have a NOS Icom AH-4 automatic tuner up in my storage locker but there’s no way to interface it to the QDX as far as I can figure, at least not without some fancy intermediary circuitry (see above, re: gathering parts).
One that doesn't is an SGC Smartuner. Just apply RF and it figures out the rest. Might sell/swap your AH-4 for the SGC version.