Yaesu Fl2100 bypass may be stuck ??

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

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Open up the amplifier (unplugged, of course!) and take some simple resistive (VOM) measurements.

    The manual with its schematic are on line all over the place, including at BAMA. Something is causing the relay to engage as soon as you apply power, and of course that should not happen. It's a pretty simple circuit.
  2. KG4RSF

    KG4RSF Ham Member QRZ Page

    thx for your help everyone
  3. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    If you need more ideas, find the proper scheme for your amp and post a link. There are a few variations of the FL2100.
    It's not a 'b'... which one is it?

  4. G3YRO

    G3YRO Ham Member QRZ Page

    All the FL2000B, FL2100 and FL2100B Amps are the same electrically, apart from the Z model, which has LOTS of differences.

    Does the Amp go into transmit mode even with the switch in the STANDBY position?

    If so, this is weird, because this is NOT a common fault . . . . however, there was a guy on here a while ago with this same fault . . . but it was hard to get any sense out of him !

    The Relay/Bias circuit is extremely simple, and therefore usually very reliable . . .

    The only thing that ought to cause the relay to be energised as soon as you turn on would be a trapped wire shorting to ground.

    Something else that would cause it to energise would be a by a short circuit capacitor - either C209 (a 2uF electrolytic), or C208 (a .01uF disc ceramic) . . . however, you would then have no Grid Bias, so wouldn't see the correct Standing Current!

    Of course, it is possible that someone has fitted an internal Relay to switch the original keying line (I did in my Amp), and that THAT relay's contacts have gone short circuit inside.

    A simple visual check and some resistance measurements (with the Amp off) should soon help you find the problem. Unlike Ameritron amps, these are well laid-out, so very easy to work on !

    Roger G3YRO
    Last edited: Mar 19, 2018
  5. W1QJ

    W1QJ Ham Member QRZ Page

    Roger, seems like this may be a common problem. The other guy you speak of (to my knowledge) never came back here to tell us if he ever got his SAME problem solved. I offered to look at it for him. A guy 20 minutes from him was bringing his amp for me to fix and suggested he get his amp to him to bring to me but that never happened. So I don't know what the other guy ever did.
  6. KA9JLM

    KA9JLM Ham Member QRZ Page

    I think the other guy hooked his amp up to the CW key jack. :rolleyes:
  7. G3YRO

    G3YRO Ham Member QRZ Page

    Yet I've never come across it !

    And as per my post, if the Amp hasn't been modified, there's nothing obvious that would cause it !

    Have to wait and see what the OP finds . . .

    Roger G3YRO
  8. G3YRO

    G3YRO Ham Member QRZ Page

    Just re-read you original post where you say the HT voltage is only reading about half scale . . .

    Have you checked what Mains voltage the Amp is set to? (maybe it's set for 220V and you're running it from 110V?)

    There are tag strips with links to adjust it, on the top front left hand corner.

    Roger G3YRO
  9. KG4RSF

    KG4RSF Ham Member QRZ Page

    Thx for your ideas. I just bought the amp at a hamfest in stuart florida. Maybe is was the amp I bought that posted before me in another post.

    ok Hope i didnt ruin anything. since the post i opened the amp and looked around. I took the top of the cage off and turn on the amp for a second. big bang. really scared me. amp shut off. I put back together and replace a fuse that blew and turned it on. seems no damaged done. what was the bang ??? Did i hurt anything

    The fellow selling it told me he converted just but in new tubes and converted to 120v
  10. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    That's the "I didn't read the manual and blew my fuse" safety interlock switch.
    Be careful in there! Don't run power amps open unless you really know what you are doing and are in the proper mindset for the task.

    See page 1.

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