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Thread: YEASU 2100B OUTPUT

  1. #1

    Default YEASU 2100B OUTPUT

    Running a icom a yeasu 2100b ...trying to tune it up just trunning up...its like the rf not going though the amp......tubes get its full tun amp off has more rf that when the amp is on.....other than the tubes what could it be......KC8HEF

  2. #2


    I have that same amp, she's a fussy one and I have yet to take the time to go through it and fix the issues. Check out the following, you might have parasitic oscillations happening.

  3. #3


    Thanks for your help,come to find out Charles it was the of my friends got a old 2100....he has a icom 730.. we hooked the relay cable up from the radio...the tooked the resistors out on top of tubes----we replaced them with 22ohm tuned up with 45 watts ok on his i used a hand keyer ok...then i started to plug a code key in the back ,radio was on 100 watts....took the resistors out again...that being an older amp could i put larger resistors in there an what size.....thank de Gary

  4. #4


    Would you want to have the auto tuner off while driving a amplifier ?

  5. #5
    K7KBN's Avatar
    Join Date
    Jul 2008
    Bremerton WA USA


    Those resistors "on top of the tubes" are not just resistors. They are "parasitic suppressors", meaning that they each have a length of bare wire, probably 20 or 18 gauge, wrapped in a coil AROUND the body of the resistor and soldered at both ends. Without that little bit of inductance in place (like with just a bare resistor), the finals will oscillate all by themselves and probably become no good in less time than it takes to say it. The manual shows the resistors as (I believe) 22 ohms @ 2 watts. You can go larger on the power side but don't change the resistance.
    Pat K7KBN
    Semper ubi sub ubi.

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