SB 200 no output

Discussion in 'Amateur Radio Amplifiers' started by W3JJL, Aug 1, 2020.

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  1. W3JJL

    W3JJL Premium Subscriber QRZ Page

    Was tuning up on 80 m and thought I had the dummy load in line found out it wasn't. Popped the hv fuse and replaced it but it went again. I changed to known good tubes before 2nd try. Any ideas? thanks John
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Transmitting into an open circuit can damage lots of things, and I'd expect damage elsewhere before the tubes. 572Bs are pretty rugged.

    Failures can include the bandswitch, the variable load cap (arc), etc. Possibly even the T/R relay. Arcs are likely when the tubes are generating power and it has nowhere to go.

    Have you carefully inspected everything inside the amp with a strong light and maybe a magnifying glass?
     
  3. W3JJL

    W3JJL Premium Subscriber QRZ Page

    I think I found it. I replced the the 100pf door knob and it does not blow the fuse. Will do some further tests to be sure. Thanks for the reply
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Good snooping!

    With any luck that was the only failed component.
     
  5. W3JJL

    W3JJL Premium Subscriber QRZ Page

    That and the fuse were the only damage. Thanks for the help. John
     
    W1TRY likes this.

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