8 tube Motorola Chairside auto radio chassis

Motorola Chairside 8 tube car radio chassis

The "Car-Side" Chairside alternate chassis
This chassis can also be found in the 1942 Motorola Chairside cabinets. See the Motorola Chairside at this link. I bought this chassis at an auction several years ago as part of a batch of items. I originally assumed that the conversion to plug-in 115 VAC had been done by a former owner. The plan was to experiment with it some day or perhaps use it for parts. I have since learned that this chassis was one of the 1942 car radios converted by Motorola and installed in Motorola Chairside sets. I repaired it after completing the repairs on the 47D2 that came installed in the Chairside. Both the D-1 and the D-2 chassis were intended for the 1942 Chrysler Corpation cars. This 8 tube set was the more expensive of the two.


Motorola D-1 chassis (36k)

Chassis Repairs
I replaced all of the audio coupling capacitors to avoid bias problems in the push-pull audio stages. Most other caps had already been replaced earlier in this radio's life. The electrolytic cap was original and in surprisingly good condition. Some testing for safety and continuity had revealed an intermittent short caused by chafing in the insulation in the wires that led to the power on-off switch on the volume control where those wires were routed through a metal cable clamp. I repaired the problem and used protective sleeving at the points where the power wires ran through the clamp and the chassis openings. The power cord was replaced with a polarized version, a fuse was installed, and the line to chassis cap was replaced with a proper one to the neutral side of the polarized cord.After these changes, a slow power up, and a bit of touch-up alignment, the radio performed exceptionally well.

Comparing the two chassis models
This model has a pair of 6V6GT tubes in push-pull for audio. It also has a nice inverse feedback circuit that improves the fidelity. The conversion uses a PM speaker. No power choke or speaker with field coil is required. Even without a choke, there is no problem with power supply hum. The sound from the PM speaker is excellent.

The 115 VAC transformer was more neatly installed in this set than the one in the D-2. It was bolted in place with two self-tapping screws. Since the required B+ voltages are higher in this set than in the D-2, no dropping resistor was used or needed. The original electrolytic cap for this chassis also had a higher voltage rating which is probably why it was still in good order. Of the two chassis installed in the Motorola Chairsides, I have concluded that this 8 tube version is the more desirable. I will keep this one as a spare for the D-2 now installed in the Chairside.



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