From the Rain City Audio Repair Blog:
This 1930 Crosley radio came through the shop for a repair recently. The owner dropped off the chassis and turntable, then took the cabinet for professional refinishing. At some point in this radio’s past it suffered major electrical damage which could have even been a lightning strike, with a burnt-out phono motor, open pickup coil, burnt up antenna coil, and open candohm sections connected to the first RF tube. Quite a lot to work on.
The chassis was very dusty when it came in, having been stored in a basement for over 80 years.
The dial bulb was missing.
Somewhat less dust under the shields, but still quite dusty. There’s a large exposed hole on the right of the chassis, and a “new” Aerovox capacitor added to the chassis.
The Aerovox capacitor replaced an original Mershon wet electrolytic capacitor, a fluid-filled copper container with a decent volume of electrolyte solution inside. They were current technology at the time, but were primitive compared with dry electrolytic capacitors that didn’t have sloshing liquid inside introduced just a few years later. It does open up airflow to some of the main wirewound divider resistors, too.
It has been serviced in the past, with several new capacitors added. One seems to have visibly failed as well. It’s a repair from the mid ’30s from the look of the components. The rest are tar block capacitors.
Most of the blocks were fairly large values.
Removing a block provided great hardware for mounting a small terminal strip in its place.
No longer limited to the values available in 1930, the 80 rectifier has a maximum 40 uF input capacitance. The Aerovox capacitor bank was replaced with two long-life 22 uF capacitors considerably larger than the originals for better power stability.
This is a TRF radio, using 7 tubes: 24 24 24 27 45 45 80. The 24s are RF amplifiers and a detector, followed by the driver/1st audio stage, push-pull 45s for an output stage, and the 80 rectifier. The first RF coil, coupling the antenna to the grid of the first RF amplifier, had a charred and blackened primary.
I attempted to measure the wire and count the turns:
While pretty, wrapped in layers of enamel magnet wire, it didn’t function as expected. That’s not a huge surprise. After a long parts search that turned up nothing substantial, I moved on to bypass the coil and make it a broadband RF stage instead. This worked, although at the expense of some selectivity.
Measurement equipment for checking the signal flow through the RF stages of the radio.
Two sections of the candohm resistor were open, they were replaced with equal resistors.
The speaker cone had been trashed at some point in the past, so it was sent off for a re-cone and came back even better than new.
Everything cleaned up nicely for the most part, although there was a scratch revealed under the dust and a section of melted varnish from the burnt up phono motor proved impervious to attempts to remove it entirely.
The phono was original but not anything special, and had an open coil in the cartridge.
The owner requested the radio be modified to take an aux input, which is an easy modification on this radio as it is transformer operated and the phono input is already capacitor coupled.
After removing the old magnet and coil, the connections were removed from the original tag strip. A new piece of protoboard with a down-mixing network replaced the old board.
While not a professional refinish, I cleaned the felt on the turntable and wiped the wood down with Howard’s.
The phono switch is a DPST, two-position single-circuit toggle switch, easily re-wired to replace the missing interconnect cable.
The full setup.
The radio tunes fairly broadly, but did easily pick up a couple of strong stations in the shop and could receive more or less depending on its final location. The modified turntable works well with an attached phone or table, and the input is switched through the original Radio/Phono switch. And after installed back in the cabinet and sent home, it looks fantastic!