A remote Power Supply for the SB-220

Discussion in 'Amateur Radio Amplifiers' started by WA6MHZ, Apr 26, 2017.

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  1. W1QJ

    W1QJ Ham Member QRZ Page

    Pat likes to punish himself. I get up in the morning eat my breakfast go down and start taking an SB-220 apart for 6 meter conversion. Although I have all I need in stock and some items pre-made I am on the air with a 6 meter conversion after dinner.
    K2XT, WA7PRC and AF6LJ like this.
  2. AF6LJ

    AF6LJ Ham Member QRZ Page

    It just occurred to me that Pat won't have any plate or grid current metering when he is done.
    Or grid bias...
  3. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    I could do that with another cabinet. But the 2 3-500Zs design has been around for a long while.
    As it is I am really rolling my own. I am just using some of the Heathkit parts . New tank circuit entirely, new input circuit, new Relay switching with QSK (Oh, Sue I need the schematic to that W7RY board so I can make my own) essentially I am building my own, just using the Heath kit cabinet.
    I know there are better options, like the GU-35B That would be lotsa power.
    That is why I wanted a CHickenbanderized SB-220, so I could build up what I needed from the ground up.
    AF6LJ likes this.
  4. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    well, I added meters to the HP-240, so the same thing can be done on the SB221RMPS. Although I really don't use meters anyway. ON the DRAKE L7, the Plate meter never has worked, I just look at the Grid meter occasionally to make sure I am not overdriving it. For tuning I use the external output wattmeter and tune for MAXIMUM output! Remember this amp will be on a HIGH SHELF, so once it is tuned up on 50.125 I won't be touching the tuning controls ever again. That is why I only need to be able to see the wattmeter on the top shelf. if the needle is wiggling, the amp is working.
    AF6LJ likes this.
  5. W4JFA

    W4JFA Ham Member QRZ Page

    Sue, Is that the plain perf board or the type that has copper on one side? Recently I had a hard time finding the "plain" type. The copper type looks like an arc waiting to happen.
    Bob WE6C
    AF6LJ likes this.
  6. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    Im liking that 120/240VAC switcher more and more now. IT simplifies alot of the project. So then I just need a 24VDC relay to key the contactor
    AF6LJ likes this.
  7. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    The remote control box can be very smqll. It has 4 connections:
    1) +26.5 VDC (just for LED)
    2) Power switch (contact closure to ground)
    3)SSB/CW (contact closure to ground)
    4) Ground

    Maybe 3 more LEDS to show current switch positions as well

    So I need 1 more 24VDC relay with good contacts on it for Selecting the SSB/CW taps on the xfmr. That saves lotsa circuitry! I need to go to Murphys
  8. WA6MHZ

    WA6MHZ Premium Subscriber QRZ Page

    So now I am seeing 4 AC Wires to the SB221 (for filament and fan) and 6 wires for the rest
    1) HV
    2) Grid
    3) 5.1V from Zener
    4) PA Amps +
    5) PA AMPS -
    6) ground

    So thats 10 contacts minimum, 4 which are heavy cable for the AC, and 6 signal lines.
    OH plus the HV and a ground strap
    I could use a run of 8 conductor rotator cable, and add a 2 wire zip cord
    Last edited: Apr 26, 2017
  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    Well you can make the meters work if you use the Heathkit HV board...

    While we are on the subject here is what you need to connect between the amplifier and power supply.

    Switched AC for the filament transformer 4 leads or two and the terminal block in the SB-221 to change the filament primary wiring.

    28V dc

    Contactor on/off

    High voltage


    Chassis ground separate from HV-

    Plate current meter +
    Grid meter +

    Nine minimum connections.

    a 12 pin Cinch Jones and a high voltage connector, a bayonet type with a shield would be the best and safest.
    The good news is....
    you only need one set of connectors, they would be on the power supply.
  10. AF6LJ

    AF6LJ Ham Member QRZ Page

    Yes that is the plain brown stuff.
    I would be unwilling to use it for anything above 600V.

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