Recently I was asked to take a look at a IC-910h VHF/UHF all-mode transceiver which had developed an issue where the bias kept being enabled. Even on transmit and when the preamp wasn’t enabled. It luckily didn’t cause any havoc as the operator’s antenna wasn’t DC shorted at the time..

If you look at one of my previous posts – you’ll know how a basic bias circuit works (check it out here – SEA remote ATU bias & mods).

The problem here, was that there was no way of turning it off and on. Nothing seemed to be burnt out or shorted on first sight. So what does this look like on the schematic?…

I recently had a look under the hood of an FT-2000; and just as I’m done repairing two FT-897; I notice that the FT-2000 should be a suspect as well! Yaesu: what gives?!

Upon opening the transceivers, I quickly saw what looked like water damage on the IF crystal filters: