Well, we all know that dry joints are caused by the joint not being heated enough when the joint is being formed. However, this one took 42 years to cause trouble!
From the serial number, my FT-101ZD was manufactured in 1981. Last week, I noticed that it was low on receive on 10m, but seemed perfectly fine on the lower bands. I came here and had a read about causes for the rig being deaf. Checked the ATT switch and cleaned it with switch cleaner, checked the continuity of the fuse bulb and checked that I was getting S9+10db on 14.2MHz from the calibration oscillator. All checked out fine. I didn't think that it would be any of them anyway as the rig seemed to work perfectly OK on other bands.
I was then looking for something specifically related to 10m, but in the end, that wasn't the case. I connected the antenna to the RX output and the sensitivity was fine, so I started looking for issues with the components near to SO239. Sure enough a dry joint was found where the inductor from the SO239 connected to the tx/rx relay nearby. A quick resoldering of this joint and my 42 year old rig was back to her former self in terms of sensitivity. I spent most of my working life in electronics, so I have seen plenty of crystaline "dry" joints in my time, but I've never known one to take such a long time before it actually caused an issue. When I looked under the sleeve (circled in the photo), the end of the inductor went through the relay terminal and was dangling loose in mid air with an obvious dry joint on the end of it. Why it only caused issues on 10m is a bit of a mystery, 12m was OK, 15m was fine too, although I guess that on lower bands the actual receive voltage from the antenna will be greater, so that may well be why. Seems a bit odd though.
Anyone can beat this record time for a dry joint to cause issues? ;-)
73 de Gordon G8WWD
