Yaseu FL-2100B Repair

Discussion in 'Amateur Radio Amplifiers' started by WA2FXM, Feb 14, 2020.

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  1. WA2FXM

    WA2FXM Ham Member QRZ Page

    I've started digging into a Yaseu FL-2100B. I don't have a lot of experience with amplifier innards, so any pointers and caveats about what I've found so far would be appreciated. I got it without tubes and knowing that the Plate meter was dead. I sent the meter out to The Meter Shop in Texas and they say it's been repaired and is on the way back. So far I've found one of the 22 ohm parasitic resistors has a slight crack in it. R207 the 47K ohm resistor in series with the safety switch has burned open. I've read about the bandswitch being a possible problem, but all 4 wafers and contact rings look clean, unscorched and unpitted. The 10 meter position contact on the back wafer was bent away from the ring but I was able to pull and push it back into position making good contact. I don't see any obvious cracks in any of the "mushroom" capacitors. The power transformer seems to ohm out ok, no obvious shorts there. Anything else I should check out before I repair the resistors and order a pair of tubes for it?

    Mark - WA2FXM



  2. W9GB

    W9GB Ham Member QRZ Page

    Yaesu/Musen FL-xxxx HF Amplifiers (Evolution of Models)
    Fox Tango Page
    http://foxtango.org/amplifiers/FL Amplifier Evolution.htm

    Ceramic HV Capacitors
    For your FL-2100/FL-2100B/**FL-2100F**

    Schematic # Description Yaesu#
    215, 224 : 100pf : K24356101 $9.20
    2212, 217 : 250pf : K24356251
    211, 216 : 200pf : K24356201 $9.20
    226 : 300pf : K24356301 $9.20
    221, 222 : 1000pf : K24356102 $9.15 (RDA30 3Kv)
    223 : 500pf : K24356501 $9.15

    Thinking of buying a used FL2100B
    or just doing an Overhaul on your FL2100B?
    Check that band switch!
    Frequent Problem :: Due to Bad / Ignorant Operators (Read Yaesu USA Bulletin)
    “Fire in the Hole”
    http://foxtango.org/amplifiers/graphics/Fire in the hole.jpg
    Last edited: Feb 14, 2020
    KD0CAC likes this.
  3. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd definitely check "why" the meter burned out. They don't just fail.
  4. W1NB

    W1NB XML Subscriber QRZ Page

    That plate choke looks like it might have sustained some damage. If the turns are shorted it will change its resonance which could create issues. Examine it carefully and if the insulation is melted, replace or rewind it. The electrolytic capacitors might also need replacing but without the tubes you really have no practical way to check the ripple under load.

    The other thing I’d do is fully unmesh the plate and load caps and examine them for arching damage.
    Last edited: Feb 15, 2020
  5. G3YRO

    G3YRO Ham Member QRZ Page

    The main PSU electrolytics used in these Amps are very high quality, and the same as used in the original FT101 series - I have never had to replace any !

    Also the MainsTransformers are very good - again I have never known one need replacing.

    The main RF Choke does look like it is damaged - very easy to rewind it, just copy the original design. (do each section at a time, hold the wire in place temporarily with tape, but put a blob of epoxy resin to hold it in place.

    The other thing to check is the Fans - they need servicing every few years. Very easy to take completely apart, clean, and lightly oil.

    Roger G3YRO
  6. VE2GCE

    VE2GCE Ham Member QRZ Page

    I agree with Roger. The only two additional things I would add are the following:

    1) Take a good photograph of the plate choke before unwinding/rewinding it.
    That way if you lose count of the number of turns and/or forget the stagger arrangement, you will have a reference photo to go back to.
    2) Then I would test the coil to make sure it does not self-resonate on any amateur frequencies.
    It is possible self resonance is what caused a section of your original plate choke wire to start to burn.
    Here is a link to an excellent explanation and test methodology of the phenomenon.
    Last edited: Feb 16, 2020
  7. G3YRO

    G3YRO Ham Member QRZ Page

    The other alternative would be to buy a choke from Ameritron . . .

    I think they use the same one in all their Amps, and it is very similar.

    Roger G3YRO
  8. K5JCJ

    K5JCJ Ham Member QRZ Page

    I suggest replacing those stock fans with modern component fans. I installed a pair of 80mm fans in mine and it made a world of difference in keeping it cool. W8JI also has a wealth of information on improvements you can make to the amp to improve stability and reliability. After changing the HV boards, tuning caps, and fans on mine it works like a champ.
  9. N8VIL

    N8VIL Ham Member QRZ Page

    When I purchased my FL-2100 (used, abused and cheap) from the estate of a CB'er, it had the same burnt area on the plate choke. The 10 meter tap on the coil was moved over one winding and had to move it to it's original position. I would check the 10 meter tap position also to see if yours may have been "modified". It may have been used by a CB'er on 11 meters and the plate choke may have resonance there (27 MHz). I restored it a few years back with improvements and works great. In 2015 I ordered the new plate choke and the doorknob style capacitors in the final cage new from Yaesu and they were still available then. Worth a phone call to see if they still are. I ordered them by the part numbers in the service manual and the parts were not expensive.
  10. VE2GCE

    VE2GCE Ham Member QRZ Page

    Good point Sean, it could have of been illegal CB use that caused that coil to burn.
    Also, another thing to be careful of when using older amplifiers on the "newer' bands (12m, 17m, 30m and 60m) is that plate choke self-resonance is not an issue.
    Last edited: Feb 17, 2020

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