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Increasing LM317 current
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drussell:

--- Quote from: Gyro on May 19, 2020, 06:51:21 pm ---One think that strikes me as a bit dodgy... Originally, the radio would have been powered by two separate batteries. The power supply introduces a current path between the two supplies.
--- End quote ---

As drawn, the original schematic has them separate, running from two different secondaries on the transformer.
Gyro:
Ah, sorry, you're right. I was thinking the high secondary voltage was being imposed by a shared secondary.

This is one of those times where the 'salvage and hoard' habit comes into its own - building a collection of multiple voltage secondary transformers!
clay1905:
The transformer used supplies two independent 15VAC outputs. For many designs, this is essential as I understand things. For "transformerless" designs, I don't think it makes much never mind.
The chassis I'm presently looking at has the usual construction, variable capacitor, big inductors, switches and valves above the sheet metal chassis base. Other discrete components below the sheet metal chassis, and then the added refinement of a shield to enclose the lower section. The power supply is mostly going to be mounted on the underside of the shield closure. The transformer fits quite well where the original one stood. It all makes for a rather neat looking modification.

It's an interesting idea, the regulator getting heated by the filaments, but no on two counts in this instance. As described, there's a bit of vertical distance between the valves above and the regulator below, and these 1.4 volt filaments hardly get warm. Even after some time the glass envelopes are only just warm to the touch.

Clay.
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