[David Dunlop]

My observations about the number of leads feeding up from the Tuning Capacitor below the COIL ASSEMBLIES proved correct. There were five of them: one coming out the left (inner) side of the Tuning Capacitor and four feeding up through the right hand side of the Tuning Capacitor cover, through small, metal sleeved holes. A bit of a challenge to get at with a soldering iron, but more on that later.

The mounting hardware for the Coil Assemblies is fairly comprehensive, involving 11 sets in total.

On the left side, there are three slot head, countersunk, machine screws. The two upper ones utilize hex nuts and external tooth lock washers on the inside of the receiver chassis wall to secure them. The 3rd screw simply fastens directly into the end of the front support rod assembly of the Coil Assembly. This rod is a three section affair and access to fit an external tooth lock washer on the interior of the left receiver chassis wall is none existent, so to prevent the support rod section at the end from unscrewing when the outer screw is removed, an external toothed lock washer was added to the left end of this outer rod section, between the rod end and the right partition wall of the Coil Assembly.

On the vertical, right rear lip of the Coil Assembly, three holes are provided which drop over three threaded studs fitted down the inner wall of the receiver chassis. With the Coil Assembles in place, three hex nuts and external tooth lock washers hold it in place.

The top, horizontal, left rear lip of the Coil Assemblies fits directly against the rear wall of the receiver chassis and a pair of round head SEMS Fasteners with external tooth lock washers goes there.

The vertical lip down the left rear side of the Coil Assemblies also has provision for three more round head SEMS fasteners and external tooth lock washers.

My approach was to remove all the hardware except the two SEMS fasteners on the top left rear lip first. Then it was easy to support the Coil Assemblies with one hand while removing the last two screws.

The Coil Assemblies is an interesting component when you get it out of the receiver chassis, for a closer inspection. In situ, and looking at it from the front of the receiver, it is clear it is built in three distinct, shielded columns. Each directly under the following Valves, from left to right: V1C Mixer, V1B Conversion Oscillator and V1A the RF Amplifier.

When you start looking at the Coil Assembly more closely, and pay a little more attention to the components identified on the back of it, you realize the three coils in each column, along with their supporting capacitors, are also laid out in a horizontal pattern of three distinct rows. The top row deals with Band 3, 7.0 to 16 MC’s. The middle row deals with Band 2, 3.5 to 8.0 MC’s and the lower row relates to Band 1, 1.7 to 4.0 MC’s.

Combining the Valves and their basic functions, along with the three columns of the Coils Assemblies, the arm waving functions of each column in relation to the Valve(s) it is linked to can be summarized as follows:

The left column is the RF Amplifier Coupling between V1A and V1C, working primarily with Valve V1C, the Mixer.

The middle column is the RF Oscillator working with Valve V1B, the Conversion Oscillator.

The right column is the Aerial Coupling working with V1A, the RF Amplifier. In the last photo posted today, you can see a long wire, with a red and yellow tracer, arcing towards the camera on the left side. This is the output lead that came from the Crystal Calibrator and travelled through the long shielding tube mounted directly above Valves V1C, B and A. The shadow of the tube is visible on the chassis back wall in the photo in the previous Post #635. This lead feeds directly into this right side column of the Coil Assemblies.

I am hoping nothing serious needs repairing on my main set receiver Coil Assemblies. It would be a very challenging component to work on, even by its own on the workbench.


David