VE6AB Antenna Werks
Atas 120 In For Repairs
In this collage of Atas 120 antenna photos, it depicts the work required to remove a sheared off fastener, one of the 3 mount-screws that hold the base in the bottom of the main tube assembly.
This is a result of water migrating in to the base-assembly with corrosion created and then the end result being a twisted off screw when an attempt is made to remove these mount screws.
An attempt at removing the seized in screw resulted in the head twisting off, and then an attempt at drilling it out by someone resulted in the tube being damaged, and the broken off screw still remaining in the base assembly.
Once I had the base assembly with the circuit board removed from the tube, I stripped the base-mount down, including the removal of the circuit-board.
If attempting this repair, use caution when removing the circuit-board, as it has to be de-soldered from the pin that is inserted in a collet that is part of the base-connector where the antenna mounts.
This pin is easily damaged if you are not careful, so proceed with caution.
Once the circuit board was removed, including the pin-assembly beneath it, I mounted the base-assembly in the milling machine, and proceeded to clean up the broken off screw by using a milling-cutter to mill it flat, as the attempt to drill it out had resulted in a irregular surface of the screw.
Once I had it cleaned up, and with the help of a centering device mounted in the milling head, I zeroed in on the screw, and then proceeded to drill it out.
Again if you attempt this repair by drilling out broken off mount-screws in the base of the Atas 120, be aware that there is a small diameter wire leading up from the bottom of the mount to the circuit-board for the center conductor, and if you are not careful when the drill-bit breaks through the bottom of the broken off mount screw, the drill bit could easily damage this center conductor resulting in un-repairable damage.
The same caution is required when using a tap to cut new threads, as you can run the tap in far enough to damage this center conductor.
I initially used a taper tap followed by a plug tap to keep this from happening. I also measured the distance to the center conductor from the surface of the hole before proceeding, so that I knew how far I could run the tap in before hitting the center conductor.
Once I had the new over-sized hole threaded for a 8-32 machine-screw, and with the base assembly reassembled, I proceeded in reassembling the bottom section of the antenna.
I also had to contend with the fact that the one of the three mounting holes in the tube had been damaged in the original attempt at removing the broken off screw by drilling through from the outside of the tube.
Never attempt to remove a broken off screw this way, as the result is the enlargement of the hole in the tube with the end result being a new place for water to migrate in to the antenna from outside of the tube.
It also creates a problem with how solid the base is secured to the tube, as the coil assembly with the whip up top along with movement of the vehicle going down the road continues to work at separating the upper assembly from the lower mount assembly.
Fortunately the hole was off center enough to still support the mounting screw, so the fix was a dab of gasket making silicone that once set up works like a gasket keeping the water out.
While the silicone sets, leave the mount screw backed off a thread or two, and once the silicone has cured, tightening the screw fully compresses the silicone gasket forming a good seal with the tube assembly.
Also when applying grease to the o-ring while reassembling, remember a little lubricant goes a long ways, whereas a lot creates different problems, especial at the top end of the antenna, allowing the lubricant to migrate to the surface of the coil-form, definitely not what you want to happen.
I find Lubriplate 105 a good choice as a lubricant for gearmotor antennas and the extreme changes in temperature that they are subjected to.
So I hope this helps you repair your Atas 120 if it comes to that, and if maintenance is done twice a year, going in to winter, and coming out of winter, the result will be a good performing antenna without major repairs required.
Click on the photo for a closer look at the procedures that were required to repair this antenna.
The sequence of photos is from top left to right and so forth ending up at the bottom lower right.
Here is a different Atas 120 being repaired....
http://www.jerryclement.ca/MachineShop/Antenna-Werks/i-tkwxDFn
