Home Forums Electronics Restoration Farm Radio A Supply Currents

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  • #6918
    Rhonda
    CVRS Member

    So I am in the process of building another battery eliminator circuit. And I was wondering what the smallest current value anyone has seen for the filament supply on the various farm radios that were produced? I have three schematics that show all the tubes wired in parallel and each of these tubes takes 50 mA of current so you would expect to see 250 – 300 mA depending on how many tubes were used in the radio. That being said, were any of the radios wired with a series or series/parallel arrangement so the A supply could also be run on 3 or 6 VDC?

    Any insight would be appreciated.

    Thanks in advance for your help.

    Gerry Shand
    780-910-7031

    #6919
    Jean Marcotte
    CVRS Member

    Hi! Gerry,

    Unfortunatly, I don’t remember the make and model number of that specific radio but while scanning the RCC manuals (from beginning to 1980) in high definition I came across the schematic of a series/parallel filament arrangement. It was an 8 tube radio from the late 20’s or early 30’s. All tubes were 2 volts, 7 had the same current value and the output tube was twice the current value of the others. So two groups of three tubes in parallel and one group with the output tube and the remaining one in parallel, the three groups in series for a 6 volt storage battery supply. Not necessarily the lowest consumption but yes, series/parallel were used.

    Jean Marcotte
    Montreal

    #6920
    Rhonda
    CVRS Member

    Hi Jean:

    Thank you for the feedback and response. That sounds promising. Making some good progress with the battery eliminator in that I have the following circuits up and running:

    1. A supply: 0-6.3 VDC, 3.5 A continuous
    2. B supply: 22, 45, 67, 90 and 135 VDC, 60 mA
    3. C supply: -4.5, -9 and -22 VDC, 20 mA each
    4. Metering boards: for a variation on a theme – build a tester
    5. Central power distribution board: got to route that 120 VAC within the cabinet safely

    Still working on the control board to slowly power up the tubes. This has been the toughest circuit to get operational with repeatability but I made a breakthrough last night. Once some more parts arrive, I can get that piece finished off and then I can start working on a case to house everything.

    With modular construction, this system can be bare bones with just the A and B supplies. Or you can add the other boards as needed to get what you need.

    More information to follow. I am not at the stage to go running down the streets of Athens naked like Archimedes and screaming, “Eureka!” but I am getting pretty darn close.

    And yes, there will be an article on this for the CVRS newsletter.

    Regards to all,

    Gerry Shand
    780-910-7031

    #6932
    Rhonda
    CVRS Member

    Still fighting with the sequence control circuit. Like Thomas Edison, I now know many ways on how

      NOT

    to do the current sensing. Still trying different topologies – tonight might yield a better result. Stay tuned.

    #6946
    Rhonda
    CVRS Member

    The sequence controller for all the boards now works successfully on my breadboard! So now to get all the circuits finished off on their PCBs and mounted in a project case.

    Cheers!!!

    #6948
    Rhonda
    CVRS Member

    Here is a block diagram of the full system (in .pdf format).

    Yes, it’s a teaser.

    Best,

    Gerry

    #6958
    Rhonda
    CVRS Member

    Ok. Got the PCBs delivered yesterday. The C supply board went together without a hitch. Now to work on the sequence control board this coming weekend. Pics to follow in another posting under the “Show and Tell” section later.

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