Adventioneering

These are antenna connector repair instructions for the Yaesu VX-7r portable H/T. I looked around the Internet for instructions when I was faced with this problem, and found none, so I thought I would share after having worked it out myself.

We’re not sure exactly how “Jordan’s New” VX-7 got broken, but one thing for sure is that it was. The SMC connector’s threaded tube had sheared off and become lodged in the antenna when it broke off. At first the solution seemed to be to just replace the connector, but then we noticed that the breach nut for the SMC was sealed with epoxy.

It turns out that Yaesu doesn’t even sell the SMC as a separate part. At first I thought that the connector must be press-fit into the case for some reason, but then I removed the old one, which was a very typical connector utilizing the same breach nut mounting arrangement as the other connectors. It’s a mystery but it probably has to do with water tightness.

The good news is it turns out the entire rear case assembly, which is made up of a magnesium-style metal with a fancy coating, was only $36US. Jordan ordered a new one, which turned out to be a surprisingly easy process when you had the part number from the service manual. I know this is typical in the radio industry (providing schematics and parts diagrams), but it was still refreshing in a world of disposable consumer electronics.

The radio seems daunting at first when you disassemble it, but I came to appreciate that it’s actually very well designed. The thing I like most about the design is it doesn’t use any press-fit connectors anywhere as are typical with Apple products. Everything is logically screwed together with a consistent set of fasteners (so consistent in fact, that while it helps to refer to the parts diagram, I could easily puzzle it out despite a pile of fasteners).

When I got the boards out of the radio, I had to remove the old puddle for the SMC center pin as well as a broken bit of pin (which I had cut to get it out, thanks to JG’s suggestion). Although this is a very dense sub-SMT board package I was able to accomplish this with a regular weller 25 watt iron and a desoldering vacuum. My original approach would have been to use braid, but this would not have worked as well.

The pin on the new SMC connector comes rotated up, away from where it has to be. This at first is a puzzle because you can’t rotate the SMC connector itself; besides the nut being sealed, the connector itself is notched and fits into the case as an anti-rotation mechanism. It turns out the pin itself can be rotated around just by force, since the insulator assembly is free-floating.
I had to trim the pin down to clear some of the mini-SMT resistors as well as the existing little bit of puddle I had left. After rotating it around there was about a 1mm gap over the puddle, which was perfect, it was easy to run a puddle down the pin.

One note here is that you should mount the RF board first, before soldering the pin. While the construction of the radio is so good the holes always seem to line up, the board can be tilted due to the spring pressure from the battery prongs. So you can solder up a great weld and then realize that the pin and SMC assembly is under a little stress, as I did. My answer was to mount the board fully, loading the pin, and then heat the puddle. The pin “popped” and the stress was released, and it was fixed.

The radio is designed to be submergible and accomplishes this through a very logical set of non-microscopic O-rings, which is also a welcome relief, especially if you have ever worked on watches. The major O-rings you will deal with are around the DC jack and then the external screws (4 in the battery compartment, 1 on the rear). The DC jack one is unlikely to break unless you are very careless, but the ones on the screws are small and fragile and you may break one or two. You can order ahead of time (I am sure they are worthless) or just see which ones go, and then order replacements.

Good luck!

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