Restoration – Chassis

Here we will discuss a restoration of a chassis for one of the antique radios. These were all tube based circuitry and point-to-point wiring rather than modern printed circuit boards. This is a 1938 Silvertone 4569 chassis which is all original. Besides the usual grime, the radio was clearly owned by a smoker given the greasy yellow film on the tubes and other parts. Normally, the chassis can be cleaned with a waterless hand cleaner like GoJo and #0000 steel wool (taking great care not to get fine filaments into tube sockets). For this case, I chose a full restoration that I call “remanufacturing” to fully strip it down, rebuild, ¬†and replace all capacitors and resistors.

This is the original underside of the chassis which shows wear and some loss of the chassis paint. Although most radios do not have a painted chassis, this one was very sharp with the metal grey overcoat. The large yellow cylinders are old paper wax capacitors which are always bad after 30+ years and the small parts are resistors which often change value with age. These will all be replaced.

In order to repair and repaint the chassis , all of the mounted parts must be removed and carefully cleaned individually to remove the dirt that can look bad plus, in many cases, affect operation of parts like switches. Notes are taken and many , many photos taken of everything to make sure all is documented on how it all goes back together!

The chassis is then stripped to get both the dirt off plus old paint. Sometimes there will be rust and that can be removed with the product Naval Jelly. Any pitted areas can be ground down with a file or Dremel wire wheel.

Often some parts are riveted into place. These can be taped off with masking tape and then several coats of spray paint can be applied. Here is a view after all of the paint has been applied and the chassis allowed to dry.

Next all of the components are remounted onto the chassis. New capacitors and resistors of appropriate values are wired into place. All wiring is restored paying special attention to the routing of the wires duplicating their original paths so that radio signals are not coupled into other parts of the circuit. The tubes are all tested using my period 1940s tube tester and new ones ordered as needed.

This is the final look of the top of the chassis, a far cry from the look of the original. Once final wiring is double checked, the radio is powered up and given the “smoke test”. Yeah, smoke is a bad thing and, if that occurs, everything must be retraced and voltages measured to find the problem. When radio stations are received, instruments are attached and test measurements done to adjust the radio for peak operation. This is called alignment.

There is a great joy in bringing these old radios back to life. The best experience is the look on an owner’s face when a radio belonging to a father or grandfather is returned in working condition and can be maintained as a great memory of that family member.