Yaesu FT857 Repair

I got a cheap, known-to-be-non-working, Yaesu FT857 that refused to turn on. There was no sing of life when pushing the power-on button, nothing. It did not take very long to find that the magic smoke inside two tiny parts was forced out to the outside world...




Once found in the schematic, it was clear that they were involved in the electronic switching of Q1031 FET, which provides power to part of the rig, which was what we were looking for:




There could be further damage, but this two parts obviously needed replacement. Not having them at hand, and being actually a few simple discrete components put together in a tiny case, I thought I could build them from discrete components and try them on the circuit. I did not take the time to look at the datasheets in order to look for adecuate replacements, I just made it as simple as possible. I took two 1N4148 diodes for the DAN222 and a 2N3904 plus two 2K2 resistors for the RT1N241 and built the following dirty little PCB:




After removing the damaged parts and wiring the project PCB to the little pads with very thin teflon wires, the rig turned on with a few relay clicks. It is always a joy to see such obvious and simple solutions to work. I ordered the parts for 1EUR, plus 6EUR shipping. This was an easy repair, the fun thing was to build the ICs from discrete components and see them working just fine.


Roberto Barrios, EB4EQA