This was my first radio to catch on fire.
This Admiral Y-2998 radio dates back to 1961 and contains four tubes mounted on a circuit board. I purchased the radio knowing it was not operating correctly with the hope of bringing her back to life.
The radio arrived with one of the tubes rolling around inside. I removed the back of the radio and noticed all four tubes were the original Admiral brand and therefore were older than 1961.
I first tested the tubes and found the 50C5 output and 35W4 rectifier tubes were both dead. I also knew I would need to replace the filter capacitor (the tall brown cardboard can) with new capacitors.
Most radios I work on have point to point wiring underneath the chassis of the radio. This Admiral radio is one of the early models to incorporate tubes wired directly to a circuit board which is mounted sideways inside the radio cabinet.
I inserted the replacement tubes and slowly brought the voltage up on the radio with my variac machine. At just around 60 volts, a .02 capacitor (C10 on the schematic) caught fire and exploded. That was a first.
Replacing the filter capacitor (the tall brown cardboard tube in the photo below) was a challenge in terms of real estate. I needed to fit three new capacitors in the same space the tall paper can sat before. Fortunately, the new capacitors were small enough to solder the negative leads together and still fit on the circuit board.
I tested the radio again with the new capacitors and tubes and was able to tune in our strongest AM station, WSM. I had trouble tuning in the other stations and decided to replace the 12AU6 and 12AV6 tubes. After installing those tubes, the radio is working properly and off to a new home.
Here she is in working condition: