[David Dunlop]

Step 3 in the removal of the Coil chassis assembly from its case is to remove from the bottom, the three screws that have washers, pictured at the end of the last post.

It was a little disconcerting to see that whoever last fitted this hardware to the case had run these three screws down so hard, the flat washers had cut into the pine board so hard the outer faces of the washers were actually flush with the surface of the board and the wood was coned inward noticably around each of the three screws. Note the first two photos. the concern here was that the base of the coil assembly these three screws are securing to the bottom of the case, is not metal. Rather, it is a mere 1/4-inch plate of brown phenolic resin. There was a very real possibility the overtightened screws could have torqued the threads they cut in the resin so much that the threads would simply strip out of the holes when these screws were removed. Fortunately, all three screws came out smoothly and there was no sign of resin dust or particles stuck to the screws. These cones in the wood will have to be filled in and levelled, and the flat washers carefully re-flattened when reassembly takes place.

The three chassis mounting screws are 3/4-inch, RH, slotted self-tapping machine screws with a 1/8-inch diameter shank and a 20 thread pitch. I have run across 1/4-inch long versions of these screws in wireless equipment over the years which have a small V-shaped notch at the tip. These longer screws do not have that notch for some reason. The threads just run out about 1/16-inch from the tip.

The flat washers are 3/8-inch OD with a 1/8-inch diameter centred hole.

At this point, the coil chassis assembly is only secured by six screws around the perimeter of the front panel. These six screws thread into six small steel brackets fitted around the inner edge of the case, each bracket held in place by a pair of small machine screws and hex nuts. See the last photo of my Parts Coil to get an idea where the last removal step is headed.


David