I have an automatic tuner from MFJ that came with a bit of FOD rattling on the inside, which I suspect shorted out the VCC. It turned out to be a snipped lead! After this, the accessory port no longer provided 13.8VDC, so my tuner could no longer be powered through my radio accessory port. Data, however worked, which I am very lucky.
Using the FT-857D Service Manual I quickly found the schematic on page 33, with the layout on page 35. Luckily for me, there was a fuse in the path, which was the most likely cascade fault. A quick continuity check proved the component bad. Although the part number in the technical manual for F1001 is KAB-2402-322NA31 or Q0000087, it’s just a 3.15A SMD fuse, which I sourced through Amazon in a 10-pack. Also, to be sure they were rated properly, I ran several fuses through my lab bench power supply to make sure they blew at the correct rating.
First I had to remove the top, followed by these screws and connectors. The front faceplate has to be removed in order to get the board out, so be mindful not to destroy the ribbon cable coming from the PA section.
Next I had to locate and remove the old fuse. I did this with some flux, solder wick, and a bit of mechanical motivation.
And then all that was left was the installation of the new fuse! It was incredibly difficult to perform the SMD work with a standard controlled-temp iron, but it was do-able, since of course, I did it!
It turned out pretty good, works well, and I’m pretty proud of my repair.
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