This project was a labour of love as they say. In the picture is an RCA 85TA 5-tube table radio manufactured around 1938. My grandfather bought it new. The radio sat on my grandparent's kitchen counter for as long as I can remember and then the radio eventually ended up in my hands.
The cabinet finish required a complete restore and the radio emitted a loud hum when I switched it on - loud enough that I switched it off right away. A sure sign that the electrolytics in the power supply had dried out. Fortunately the tubes all checked out OK and all the mechanical parts were fine. I obtained a schematic for the radio and set to work.
Once the chassis was opened up, inside looked more like a kind of electronic stew - a jumble of brown, waxy tubular capacitors and resistors connected point to point with every connection firmly attached before being hand soldered. Not as neat and tidy as modern PCB construction but still very functional.
I replaced the wiring as most of it had badly deteriorated and I replaced all of the resistors, "paper" capacitors and the electrolytics. In addition, the power transformer pigtail wires had deteriorated and required the transformer to be opened and new wires attached to the primary and secondary taps thereby avoiding finding a replacement.
Here is a view of the inside after restoration. The chassis was a mess (see picture below); rusted in some areas. I cleaned it up and painted it. I also added a fuse. Notice the new electrolytics. The originals were the height of the IF transformers on the left and were about 1.5" in diameter and had completely dried out and had to be replaced. I know that many radio restore "purists" would have kept the original cans and put the electrolytics inside the chassis. However, I had already painted the chassis and stained the cabinet and applied a satin polyurethane finish, so what the heck. I made some PCB adaptors to mount the electrolytics as shown. Again, not true to its original form, but resulted in a very clean job.
The cabinet is a furniture piece with beautiful matched dark walnut veneer. The four controls: power/volume, tone, band (AM/SW) and tuning have unassuming brown bakelite knobs. The tuning dial is lit from a bulb that sits behind the dial pointer. It is clear that this radio was intended to be a really nice addition to the home.
A few interersting things about this radio. The tuning dial has presets for popular radio stations. One button is labeled "KOMO" and that station is still broadcasting from Seattle WA.
The other interesting thing about the radio is that it uses a "grid bias" battery for the audio stage. The acorn sized battery had long since dried out. I replaced the battery with an adaptor I made that uses a small lithium coin cell and a voltage divider to get the 1.25V needed to bias the grid. The tuning circuit is a heterodyne type, a relatively new technology to radios of this vintage.
One final detail: Inside the radio cabinet is a warning that a license was required to operate the radio. The $50.00 fine would be about $750 in today's dollars. The prison alternative to paying the fine seems a bit steep.
