So after more than 1 year on my bench I finally took the time to repair my old FT817ND. It suffered from an overvoltage event and a lot of the internals were damaged. I became a member of the BFC or blown finals club. After buying a replacement finals board and installing it I noticed the ALC circuit kept tripping and preventing any output.

The issue was traced to Q1098 on the schematic wich is an novel overcurrent protection circuit. The opamp amplifies the voltage drop over the 13V input transformer, when it goes high it shuts down the 68 MHz IF to prevent further damage Pulling the outpout of Q1098 low restored the output power on my FT817. A replacement opamp will be bought next time I order from mouser.

With the new finals board installed and the bias point set I did have to edit some calibration constants in the soft menu to reach full 5W output power. I had some trouble getting a reliable power meter. I didn’t want to pull out my HP436 power meter and an assortment of attenuators so I used a basic DAIWA SWR / Power meter left over from my father-in-law only to find out the 20W range didn’t work. After locating the schematic and opening up the power meter I quickly find a broken ceramic capacitor on the 20W range to deflect the forward power meter.

Still I didn’t have any faith in the displayed power level on VHF and then I remembered I have a Bird 43 power meter which was a gift from a collegue. With the correct slug I can now say I know that my FT817 is again outputting 5W on HF, VHF and UHF.