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Yaesu Fl2100 bypass may be stuck ??

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

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  1. KG4RSF

    KG4RSF Ham Member QRZ Page

    Thank you all for your help. You are a great bunch of guys. Although i have by general, I'm not good with tracing anything

    but traced it to tube. It was the tube.

    Thx everybody

    The relay only comes on when triggered. Tonight i am going to power it up

    I may have more questions

    After tracing everything. removed tube and put it back in and it worked.. These tubes can go in anyway. Might have been in wrong. I had just bought amp
  2. KG4RSF

    KG4RSF Ham Member QRZ Page

    traced from bias variable resister at the end of resister had a lead going to relay also going to resister by but the tube and still had reading of 57 ohms. removed tube to test and put back in and it worked Roger.
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Well all I can think is that you had a tube in wrong, such that the grid circuit was connected to ground via the Filament.

    The tubes normally have a metal lug sticking out of the side of the base - when the tubes are plugged in (horizontally) this should be pointing upwards - and in fact the clamp round the base can only fit when the tubes are the correct way . . . so not really sure how this could be possible, unless the previous owner didn't tighten the clamp?

    Anyway, glad you found the problem.

    Roger G3YRO
  4. W1QJ

    W1QJ Ham Member QRZ Page

    Sounds like the last guy who had a similar problem but he never returned to let us know what happened. Maybe he is still trying to fix it.
  5. KG4RSF

    KG4RSF Ham Member QRZ Page

    not so fast. plate voltage 2kv ip=0 my frind said with new tubes have to adjust bias. Could that be it ? Can't find instruction in manual. does anyone know ling to a SERVICE Manual ??
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    2kV is very low, should be 2.4kV (but maybe multiplier resistors drifted). I would be good to verify with an independent meter if possible -- but be very careful!

    Ip = 0 when the amplifier is KEYED and in the XMIT mode? Something's wrong.
  7. G3YRO

    G3YRO Ham Member QRZ Page

    You NEVER normally need to adjust the bias on these Amps . . .

    There's a big wirewound resistor with a clamp on it, that is set at the factory.

    I have replaced dozens and dozens of sets of 572Bs in these Amps, and NEVER had to adjust it. The standing current is always well within spec. (as long as you use the proper Cetron or Chinese Valves, not the Russian ones, which are completely different)

    So it sounds like you still have a fault!

    Yes, I would first VERY CAREFULLY measure the HT voltage on top of the big RF Choke in the PA compartment, if you have a suitable meter. (remember, this is a lethal voltage!)

    So you get no indicated Standing Current at all when the relay goes over?

    What happens when you drive it with RF? Does the meter indicate PA Current then?

    Do you get RF out OK?

    Roger G3YRO
  8. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Last edited: Mar 24, 2018
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Yes, you could do that. What meter would you use? Where exactly are the measurement points? How do you secure the leads and interlock so the task is safely performed?

    If you are going to suggest this, it may be nice to explain things to the OP so he doesn't have to guess about what to do.

    It may be easier to tell him how to measure the meter multiplier that possibly has gone high in value.
    Last edited: Mar 24, 2018
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    Everything is in the operator manual.



    You will need a High voltage probe mad for measuring the plate voltage.
    Last edited: Mar 24, 2018

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