06-10-2026, 12:39 AM
We picked this up a couple months ago so she could have a radio for herself that had a bit of color to it. It's AM only which makes it relatively breathable in the chassis, looks to be our first permanent magnet speaker, and there are some good options for how to mount an aux input and switch.
I figured I'd see what it needed for capacitors and resistors tonight since this will be the next project. It's not bad, again, I think thanks to the simplicity of having only one band to listen on, but I do have a question. In the photo below, circled on the right side are two 4.3k ohm resistors in parallel that are a bit beefier than most of the others in the radio. This is supposed to be R3 according the to schematic I downloaded and it calls for a 2.2k. Testing in-circuit yields 2.9k, so its out of spec either way.
The documentation I was able to find online was all of two pages, the first was the schematic itself and the second was the alignment procedure. No parts list. To my surprise, the schematic and parts list were glued inside the top of the cabinet. On this parts list, the capacitors are numbered according to their identity on the schematic in the cabinet, but diverges from the numbered parts on the schematic I downloaded - no biggie. The resistors, though - no numbers, just values and wattages. Interestingly, while the schematic in the radio agrees with the schematic I downloaded that the resistor in this location should be a 2.2k ohm, it doesn't list a 2.2k ohm in the parts list, instead, a duplicate of the 22k ohm exists, despite there only being one 22k ohm resistor in the radio, so it seems clear that this is a misprint on this part list label.
All that is to say, I don't have a good indicator for what the wattage of the 2.2k ohm R3 is supposed to be, and the parts that are in place are sized such that they could be a 2W, but there is only one other resistor in the radio that is bigger than 1/2 W - the 1k ohm between the two electrolytics. Would it make sense to need a 2W resistor all this way over in the RF section? Further, though perhaps less important, does this seem like it would be a later modification? Aside from the power cord, I'm not sure if there's any indication that this radio has been worked on so it seems strange it might have come this way from the factory. Would there be any advantage to doing the two resistors in parallel as it is right now, or should I simply go with a single 2.2k ohm?
There are only two other resistors that need changing, one, circled in the photo all the way to the left, actually physically is broken - maybe exploded? It was supposed to be 150 ohms, tested at 8, and it's right where power comes into the rectifier. The other gave such a flaky reading I did snip one lead to test it out-of-circuit and it was still way off: supposed to be 6.8M ohm, tested really low before drifting upward and settling in around 2.2M.
As for capacitors, two electrolytics to replace the dual can, 8 paper to be replaced, one mica being left alone and two small, ceramic dog bone-looking ones which I think, based on my reading, should be treated like micas and only replaced if we chase a problem down to them. Almost all pretty accessible to swap out. Definitely some different philosophies from the Philco and RCA I've worked on as far as wiring to ground.
On a separate note, I think I figured out why my IG-102 signal generator wasn't producing a signal. It has a 12AT7 tube with the very pretty white film at the top of the tube. The other tube in there, a 6AN8, has normal coloration and does glow when powered on; the 12AT7 does not glow. There's also a 20-20 dual electrolytic can in there, so I figure I may as well replace that with new electrolytics when I order. Most everything else is ceramic and looks sound. Wish I would have checked the tubes visually before I ordered this last time.
Best wishes,
Roy




