Note for IC-9700 users. Possible Fault due to heat stress on the LDMOS


On request from VK3ZYZ

Note for IC-9700 users.
I noticed some intermittent power drops on my 9700 over the past few months when using on SSB and other modes, but nothing noted on digital modes where I run at lower power of 20W. Last night I noticed a burning small in the shack and managed to track it down the the 9700. After some tests, I could see power fluctuations from zero output to 70%. Upon opening up the rig the problem was self evident, with dry joints on the MOSFET pads where they connect to the board. This rig is only 18 months old so this is not expected. The root cause is poor soldering from the factory and two other members of the WSPR group have noted the same issue on their 9700s, with one user having the PA go up in smoke, most likely caused by excessive heat from sparking. I have resoldered the pads using lead based solder, but I would also recommend adding a solid wire from the top of the pads to the base of the coil to take some of the current out of the track and make the connection more robust.
I would recommend to all 9700 owners to open up their rigs and check for a discoloured track and dry joins on the final device as noted in the diagram.