Yaesu Fl2100 bypass may be stuck ??

Discussion in 'Amateur Radio Amplifiers' started by KG4RSF, Mar 18, 2018.

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  1. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Hi Marc,

    What I have to write here is meant as friendly advice and not disparaging in any way. Not everyone should be poking around and guessing about what could be wrong inside a power amp.

    When seasoned amp repair people see posts in this forum, they have to make a judgment about the ability of the poster to take and follow direction without putting themselves in danger. I'm not speaking for anyone else on the Zed, but what I'm gathering from this thread so far isn't giving me the impression of safety... actually it's quite the opposite.

    It's one thing to learn about repairing equipment when the voltages and power is under a certain place, (say 400v and a hundred ma.) like what is inside a tube receiver, or 14 volts in modern transceivers. Poking around in the above equipment can hurt but is unlikely to be deadly with a simple mistake. Tube power amps are a different animal entirely. Every connection must be properly done. Every test must be properly conducted with a clear idea of what is being done and why.

    With this amp, I would recommend finding some local help with someone who knows how to work on power amps and has the correct bench and tools to do so, or ditch the unit and find a working one.

    Wishing you safety and all the best,

    Chris in NYC
    Last edited: Mar 21, 2018
    KS4W and KA9JLM like this.
  2. KG4RSF

    KG4RSF Ham Member QRZ Page

    the meter looks like the one in pic the 2 is about 3/4 way to full
  3. KG4RSF

    KG4RSF Ham Member QRZ Page

    no jumper installed (the alc has screw removed, not the wire just the screw
  4. NJ9P

    NJ9P Ham Member QRZ Page

    Or, in my case, the "it's two in the morning but I'll work on this for just ten more minutes" resistor.
    KD2ACO likes this.
  5. G3YRO

    G3YRO Ham Member QRZ Page

    On the HT Voltage meter, each division is 100 volts, so if it is two marks above the 2, that is 2.2 kV . . . if so, your HT voltage is looking a little low . . . but that might be due to the meter shunt.

    You didn't answer this question - Does the relay go over REGARDLESS which position the STANDBY / OPERATE switch is in? Ie if you flick that switch up and down, can you hear the Relay click on and off?

    Make sure the SWR / IP switch is ALWAYS in the IP position (so it monitors the PA current) . . . are you saying that this meter always stays at zero?

    Roger G3YRO
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page


    We always called that a "multiplier" resistor, to change a milliammeter to a voltmeter.
  7. K4LMP

    K4LMP Ham Member QRZ Page

    It's called a shunt, because it diverts most of the current away from the meter. The resistance value of the shunt is calibrated, so the meter reads correctly.
  8. KG4RSF

    KG4RSF Ham Member QRZ Page

    first thanks to all of you !!

    The relay closes when i turn unit on, regardless of what switches are set to what.

    So I Loose most of receive signal when i turn on amp. No terminal are on back. Nothing shorted on terminal. No shunts
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    The OPER lamp comes on also ?
  10. G3YRO

    G3YRO Ham Member QRZ Page

    I presume the OPER lamp comes on and off as you turn the switch from STBY to OPER, right? (but the relay stays ON)

    And what is the PA Current meter reading? (I keep asking this, but you're not answering!) - make sure the meter switch is in the IC position, not SWR.

    Are you able to follow the circuit diagram and do some resistance measurements with a multimeter? (with the amp turned off)

    Roger G3YRO
    Last edited: Mar 22, 2018

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