Receiver Wave Change (Band) Switch S6A
An interesting day working on the Main Set Receiver yesterday. Some mysteries solved. Some new ones added to the pot.
The first thing that came to light, literally, was the discovery of a cracked outer terminal wafer on the Wave Change (Band) Switch, S6A, located on the upper right side of the receiver chassis. I had never seen this before, and initially thought I had been the cause as this switch sits right where ones hand instinctively goes to grasp the upper side of the chassis assembly when picking it up. The only reason I noticed it was because the work lamp on that side of my bench was on when I put the receiver down and the light created a shadow on the wafer that caught my eye. A close inspection, however, revealed the inner core of the fracture was not fresh, but had discoloured over a period of time.
In the attached photo, the crack runs through the empty 5th terminal position, between the two occupied terminals at the 5:00 position on the wafer.
Studying the wafer, I then noticed the none factory soldering point on the top right most terminal, where a new, plastic covered lead was soldered into the bottom side of the terminal, rather than onto the actual terminal itself that faces inward on the other side. This new lead runs up to the S5A Relay up behind the 8-Pin Connector on the back of the receiver. My thinking is that a repair was done at some point where the two retaining screws for the wafer were removed in order to pull the wafer forward to access the necessary terminal to effect the repair, There are several heavy gauge, solid copper wires soldered to this wafer and they likely resisted moving forward at the expense of cracking the wafer. The rotating contact plate and terminals on this outer wafer are still interacting correctly, so the old lead was likely cut away, the wafer carefully reinstalled and the new lead soldered to the bottom of its terminal.
That was the most exciting part of the days work, but I now know to take extra care when I dismantle this S6A switch from my Spare Parts Receiver down the road.
David
|