One more coat of clear lacquer and a light buffing will finish my complete(and ridicuously expensive, thanks the price of known-good O1A tubes) restoration of a beautiful Silvertone-branded King 10K1 Neutrodyne receiver.

Okay, I do have to finish building my battery eliminator power supply, but that should be the work of a couple of hours at most. At any rate, I need a question answered before I power this thing up. We have the expected "A" battery connectors, plus 90V and 45V binding posts AND a mysterious (to me) pair of posts for + and - 4.5V. These are jumpered together with cotton covered wire that looks original. What were these for?

:One more coat of clear lacquer and a light buffing will finish my complete(and ridicuously expensive, thanks the price of known-good O1A tubes) restoration of a beautiful Silvertone-branded King 10K1 Neutrodyne receiver.
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:Okay, I do have to finish building my battery eliminator power supply, but that should be the work of a couple of hours at most. At any rate, I need a question answered before I power this thing up. We have the expected "A" battery connectors, plus 90V and 45V binding posts AND a mysterious (to me) pair of posts for + and - 4.5V. These are jumpered together with cotton covered wire that looks original. What were these for?

My guess would be they are for the "C" battery, the one for grid bias. Will check more and let you know.
Lewis

I would have thought the 4.5V posts were for a bias supply (C), too, but, I'm confused by the old jumper between the positive and negative terminals. I'm also curious as to the reason for the existence of both 90 and 45 volt B battery connections.

Hi Craig

Not all buyers of radios used C batteries. When a person didn't use a C batterey C- was connected to A-.

Without a C battery more current will be drawn from the B battery. When higher voltage B batteries are used even greater negative C voltage are needed.

Best to use 3 penlight batteries for the C supply. No current will de drawn so batteries will last their shelf life.

Norm

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: : : : : : : : : : : : :Refer to the green buss markup on the Reference schema below. : : : : Indeed, that last mentioned supply is the C bias source and is responsible for the 1st grid biasing of the last two audio tubes in :your sets receiver tube complement. : : :Look at the different B+ supplies routings flow and you will see that the +45 is the supply level for the 1st audio /detector stage :of the unit. : : : : : : : : : : : :73's de Edd : : : : :

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: : :KING_Model 10K. . . . . . MARK-UP SCHEMATIC : : : : : : : : : :

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Thank you Norm and Edd!! The shroud of ignorance has been lifted. The markup schematic is a tremendous boon.