I pulled the two chassis and took them to the bench for a better look. The amplifier is really heavy. From the front
you can see that someone has placed some sort of clear plastic over the speaker cone and taped it in place. Attempting to remove the tape pulls the fuzz off of the fuzzy brown surround, so for now I am leaving it in place.
Things look pretty good underneath.
Two nominal 8K resistors each measure 10K, and the nominal 70K comes in at 50K. The other three resistors are all spot on. I am thankful that I have the pictorial as well as the schematic since the wires are mostly in a harness and the colors have so faded that is impossible to trace them directly.
However, the pictorial and schematic as printed are too small for my old eyes to read even with my reading glasses, so I blew them up to double size, printed them on four sheets each, and taped them together.
My wife's stuffed bunnies enjoy trying to make sense of them.
So now to work.
I finally decided to disconnect the old filter caps even though they test ok and leave them in the can in case someone coming after me wants to undo what I have done. I really like the idea of trying to make reversible changes. So first I disconnected all the wires and resistors connected to the filter caps.
All the wires are tagged with the numbers assigned to the connectors on the filter cap can.
Then I mounted the new metalized polypropylene caps on a piece of perf board and on the other side, I re-created the layout of the connectors on the original cap can.
Here it is installed.
I mounted it on four metal standoffs which I epoxied to the underside of the chassis. I didn't want to drill new holes. This way someone later can undo what I have done.
Today's quiz: Can you find all 6 resistors in this picture?
Turning the chassis right side up, I check to make sure the fuse in installed in the correct place.
Installed to the right, it connects to the 120V tap on the power trans. To the left, it connects to the 110V tap.
I added a label to the now disconnected cap can so that anyone coming after me can see what I did.
So here we are,
ready for the smoke test.
I put in the rectifier and the power supply voltages were about 5% above nominal. Put in the rest of the tubes and connected the radio chassis. The plate and screen voltages again are about 5% above nominal. I get a satisfying hum on touching the grid of the first audio amplifier, but no radio sounds. So it looks like the power supply and amplifier sections are working ok. Decent progress for the weekend. Tomorrow I'll start messing around with the radio.