SB-200 half power out

Discussion in 'Amateur Radio Amplifiers' started by KU7I, Nov 8, 2019.

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  1. KU7I

    KU7I Ham Member QRZ Page

    I have always had good luck with the Chinese 572Bs I buy from K5SVC off of Ebay. Over the years I must have purchased at least a dozen or more. This time, one of them caused a loud bang in my SB-200 after a minute of initial testing with this latest new purchase. As soon as I heard the bang I smelt smoke, then the filament went off. I replaced the suspected bad tube with the former known good Cetron. Filament came on but after some troubleshooting it seems that tube position is not getting RF into it. The filament is on, good HV on the anode but I am sure something opened up on the input side...possibly the grid resistor that goes to ground?

    Ideas?

    Lane
    Ku7i
     
  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Sounds likely. A flashlight, voltmeter, and open case are your good friends.

    Sorry about the bad tube. That happens once in a while.
     
  3. WA7PRC

    WA7PRC Ham Member QRZ Page

    This question also posted on eHam (link).
     

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