Early version of SB220

Discussion in 'Amateur Radio Amplifiers' started by N4IDA, Jun 30, 2019.

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  1. N4IDA

    N4IDA Ham Member QRZ Page


    I’m wondering if someone might help me identify what appears to be an early version of the Heathkit SB220.

    I was given a SB220 several years ago. I pulled it off the shelf recently to open it up and see what I had.

    Upon examining it and comparing it with my SB220 that is already in use it appears it’s an earlier version of the amp compared to mine.

    One of the obvious differences is the load capacitor.

    My amp has a 2 section load cap, with connections going out the bottom, while this older one is a single section cap with its connection in the main RF section of the amp.

    Is this enough info to help me identify this amp.

    Also would you mind helping me find the manual for this older version?


    Al – N4IDA
  2. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Pictures would help a LOT!

    N2EY likes this.
  3. N4IDA

    N4IDA Ham Member QRZ Page

    Ok. I'v let a friend of mine take the amp back home with him in another state. I'll get some pics together.
  4. K9STH

    K9STH Ham Member QRZ Page


    My SB-220 manual shows a single section antenna loading capacitor and I have it in PDF format. Contact me, by E-Mail, at

    k9sth (at) sbcglobal (dot) net

    Glen, K9STH
  5. W1QJ

    W1QJ Ham Member QRZ Page

    The single version is the newer model and the dual section is the older model you have it backwards.
    N2EY likes this.
  6. WA7PRC

    WA7PRC Ham Member QRZ Page

    I have both manuals on my website. I redrew the schematic for the later version that shows C57 as a single-section part.

    When I redraw a schematic using a vector drawing application (Visio) and "print" to PDF:

    • No matter how far you zoom in, text & line remain SHARP.
    • Since nothing is scanned, every hardcopy is a 1st generation printout.
    • Text is searchable.
    • Compared to a scanned image (a yuuge pile o' pixels), file size is itty-bitty.
    I can't do anything about the rest of the manual, :-/
    N2EY, AF7XT and W7UUU like this.
  7. W2VW

    W2VW XML Subscriber QRZ Page

    Does the earlier version have a zener for bias or is it zero bias?
  8. N4IDA

    N4IDA Ham Member QRZ Page

    Oh! I stand corrected.
  9. N4IDA

    N4IDA Ham Member QRZ Page

    What do I need to do to get those new drawings? Would appreciate it. My buddy and I are in hot pursuit of recovering violated Heathkits.
    Al - N4IDA
  10. W1QJ

    W1QJ Ham Member QRZ Page

    All sb220 amps had around 5.6v of operating bias. The original ones had a 5watt axial zener with a finned heat sink right on the rectifier board. Later models had the 10 watt zener mounted to the side panel. Unfortunately with a major discharge of energy even the 10 watt zener bites the dust. The string of diodes used in aftermarket boards with 1n5408’s live through most gas off events.
    N2EY and W2VW like this.

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