ad: chuckmartin

Yaesu FL2100B with bad caps.

Discussion in 'Amateur Radio Amplifiers' started by N8CMQ, Feb 13, 2019.

ad: L-HROutlet
ad: l-rl
ad: Left-3
ad: L-MFJ
ad: Subscribe
ad: MessiPaoloni-1
ad: K5AB-Elect-1
ad: Left-2
  1. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    My continuing saga of the FL2100B I am trying to get working keeps on getting longer...

    On 80 meters, the amp is perfect, but on 40 meters, the loading control has to be on 0 to get max output.
    I suspect a bad cap, as there are one or two I have to change yet, OR bad contacts on the band switch.
    This is with the amp terminated into a 1000 watt dummy load.

    I also found I had installed the wrong inductors on the tube supressors when I tried tuning up 10 meters!
    I let the smoke out of the supressor resistors! That was fun! I cut the inductors down to the proper turns count...
  2. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Are the wafers and wires lined up correctly? See if S1B and S1A are breaking the padder connections on 40. Is there a solid connection shorting out the 80-40 taps of the coil when in the 40m position?
    Last edited: Feb 13, 2019
  3. G3YRO

    G3YRO Ham Member QRZ Page

    When you say the Load control is on 0, I presume you mean the variable capacitor is fully meshed?

    The simple answer is no ! As there are are NO fixed padder capacitors in circuit on 40m and above . . .

    Of course, if you're lacking the abilty to drive the amp up to full power, max output WILL occur with the Load variable at 0 . . .

    What rig are you driving the Amp with? Bear in mind these Amps were really designed to be used with the original FT101 series, which give 130 - 120 watts output.

    What is your dipped PA current on 40m?

    Roger G3YRO
  4. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    Hi Roger, I have only used 30 to 50 watts input when testing the amp out.
    Dipped current is around .3 on 80 meters, and .2 on 40 meters.
    So I have to stop babying the amp and input more power?
    I can do that, But I was trying to go easy as I learn the amps behavior.

    As it was, I have about 500 watts output, with a clean signal. On air reports are good too!

    I have an Icom IC735 that can put out 120 watts or so, it should drive the amp to full power if I turn it up, I was just trying to prevent the smoke from coming out. I want to add grid current metering capability before I start going high power tho. I was thinking of adding a switch and shunt to use the existing meter to read grid and plate current.

    So far the amp is working well with the mods and repairs I have performed.
    I need one or two caps for the tank before I go too far tho.
  5. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    Hi Chris, the switches are lined up and the contacts checked out, but I did not check for jumpers that should not be there.
    Is it possible that I am not driving the amp hard enough as Roger says? I am only driving it with 30 to 50 watts to test it out...
  6. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Yes! Depending on how S1b is made (shorting between these pins?) you may be able to move C226 to the next lug and pad 40m a bit more, or do the equivalent as your soldering gun steers you towards your needs.

    Sounds like the amp is running efficiently and giving you what you need with lower drive (which is good!). As Roger points out, if you bring up the juice, the loading may move into range.

    40m padding.jpg

    click for bigger pic
  7. G3YRO

    G3YRO Ham Member QRZ Page

    Yes, at low power levels you won't be able to Load it properly . . .

    Drive it with 100 watts plus and then you'll load it to full power - dipped PA current of around 400 mA ! (and into a 50 ohm load the Load control will end up around 4 )

    I worked for Yaesu when these Amps were a current model . . .

    Roger G3YRO
  8. N8CMQ

    N8CMQ XML Subscriber QRZ Page

    Hey Roger, you are right.
    I put 100 watts in, I got 900 watts out, slightly more than .4 ma on the plate current.

    Now I have an antenna problem...
  9. G3YRO

    G3YRO Ham Member QRZ Page

    Exactly !

    Although I'm afraid your Power Meter isn't reading correctly . . . you will actually have about 600 watts output. (corresponding to about 1200 watts input power)

    Roger G3YRO
  10. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    You need to drive it with 100 watts to get 600 out? <8dB gain? Sounds a bit low to me... well into compression at that point if 50 gives you 500 out, which sounds more in line with a pair of 572’s to me.
    Last edited: Feb 14, 2019
    N8VIL likes this.

Share This Page