02-06-2020, 08:28 PM
Hi all,
I have several 37-620 chassis and am restoring my second one. I have done one already. Even between code 121's there are differences. There are differences between the code 125's. There are differences (maybe errors) in the schematics. the biggest problems are in the number of coils in the RF chassis done during various production runs. Some changes include the original number of coils and compensating capacitors. Later production runs have fewer coils and fewer compensating capacitors on the underneath side of the chassis. The run with fewer coils and caps changed the tuner with compensating caps as part of the tuner. I have also found the coil resistances as indicated on the schematic may often be different than what the coil actually is. this was usually a minor change during a production run to improve performance and or reduce costs.
Removing any of the coils for a rewind is not for the faint of heart. The wires are very small and fragile. Some of the coils are wound/terminated with llintz wire. The key is using the correct wire and rewinding exactly like the original.
Best results are obtained by removing the RF chassis and then removing each of the three sections and working on each section in something like a Pana-Vise.
The easiest way to remove the RF chassis is to unsolder and tag each of the wires going to the RF chassis. Next remove the dial components. Then remove the power switch/tone control and lay to the side (don't unhook the wires to it.) Next remove the hex screws holding the front chassis plate keeping the volume control shaft attached to the plate (don't lose the clip on the VC). Finally remove the rear screw/rubber holding the RF Chassis to the rear chassis plate. Finally tilt up the rear of the RF chassis and slide forward for removal. It may not slide out easily as the rubber grommets may have decomposed and corroded on. Once the RF chassis is removed, you can remove the side covers and remove section, tagging any wires necessary to take out each section.
Be careful around the coils. They are fragile! You can then carefully remove and replace or rewind the defective coil.
Take lots of photos prior and during disassembly. Also make a line by line step log of all wires/steps as you go. Reverse all steps to put it back together. I hope this info helps.
Gerald D.
I have several 37-620 chassis and am restoring my second one. I have done one already. Even between code 121's there are differences. There are differences between the code 125's. There are differences (maybe errors) in the schematics. the biggest problems are in the number of coils in the RF chassis done during various production runs. Some changes include the original number of coils and compensating capacitors. Later production runs have fewer coils and fewer compensating capacitors on the underneath side of the chassis. The run with fewer coils and caps changed the tuner with compensating caps as part of the tuner. I have also found the coil resistances as indicated on the schematic may often be different than what the coil actually is. this was usually a minor change during a production run to improve performance and or reduce costs.
Removing any of the coils for a rewind is not for the faint of heart. The wires are very small and fragile. Some of the coils are wound/terminated with llintz wire. The key is using the correct wire and rewinding exactly like the original.
Best results are obtained by removing the RF chassis and then removing each of the three sections and working on each section in something like a Pana-Vise.
The easiest way to remove the RF chassis is to unsolder and tag each of the wires going to the RF chassis. Next remove the dial components. Then remove the power switch/tone control and lay to the side (don't unhook the wires to it.) Next remove the hex screws holding the front chassis plate keeping the volume control shaft attached to the plate (don't lose the clip on the VC). Finally remove the rear screw/rubber holding the RF Chassis to the rear chassis plate. Finally tilt up the rear of the RF chassis and slide forward for removal. It may not slide out easily as the rubber grommets may have decomposed and corroded on. Once the RF chassis is removed, you can remove the side covers and remove section, tagging any wires necessary to take out each section.
Be careful around the coils. They are fragile! You can then carefully remove and replace or rewind the defective coil.
Take lots of photos prior and during disassembly. Also make a line by line step log of all wires/steps as you go. Reverse all steps to put it back together. I hope this info helps.
Gerald D.
