Yaesu FL-2100B Plate Choke Rewind

Discussion in 'Amateur Radio Amplifiers' started by N8VIL, Oct 21, 2015.

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  1. G3YRO

    G3YRO Ham Member QRZ Page

    Personally I would have re-wound the RF Choke, for a few dollars worth of wire!

    (although I am astounded how cheap a replacement is . . . I remember them costing almost that much 35 years ago, when I worked for the UK Yaesu importer!)

    Wish I could understand why anyone modifies the original bias circuit . . . the valves are fully cut-off on receive, so what is the point?! (and it's a much simpler and more reliable circuit than in the later FL2100Z version)
  2. N8VIL

    N8VIL Ham Member QRZ Page

    I was amazed the choke was even available. I had some other parts to order from Yaesu so for the price I ordered it. I might rewind the old one for a spare and to see how neat of a job I can do. Any idea on the wire gauge?. After reconsideration I should have left the bias circuit alone as it was probably more than adequate. I am going to leave it as it is for now as the amp is working good but a little finicky on 80 meters. Live and learn..
  3. KM1H

    KM1H Ham Member QRZ Page

    I guess you missed out on the reason maybe 20 years ago when Svetlana marketed their 572B version which was far from cut off, as was the Cetron, and would take off in standby. RFP and other Svetlana sellers published the revised circuit on their web pages which is FL-2100B specific.
  4. W1GCI

    W1GCI Ham Member QRZ Page

    Rather than starting a new thread, I thought I'd extend this one since my concerns are aligned. I recently acquired an FL-2100B. When examining the amp, I discovered a burned segment on the RF Choke and what looks like a solder blob on top of that segment - perhaps someone's attempt to repair the choke. My question, however, is related to why these chokes seem to be prone to burning and it seems it's always in the segment in the middle of the choke. Is the choke resonating at a frequency that causes excess current? Is it the physical location of the choke? I can repair the choke without difficulty, but if it would be better to have a different configuration for the choke that is less prone to failure, I'd much rather do that. I see discussions about repairing but not about modifying. What's the best approach to a lasting fix?
  5. W9GB

    W9GB Ham Member QRZ Page

    FoxTango web page on Yaesu FL-2100 HF amplifiers has ALL those Yaesu part numbers,
    Plate Choke, HV Capacitors.
    http://foxtango.org/amplifiers/FL Amplifier Evolution.htm

    Scroll Down that web page and Read.

    Plate RFC Inductor Yaesu P/N : L10220655

    There are 10 capacitors referenced.
    Ceramic Capacitors for the Yaesu FL-2100/FL-2100B/**FL-2100F**

    Tom, W8JI wrote an entire article on this subject, RF Plate Choke.
    SHORT Answer: Many of these Plate Chokes have series resonance at 27 MHz.
    Not an issue for licensed radio amateur, illegal CB operator destroys choke (no tech knowledge).
    Last edited: Aug 28, 2016
  6. W1GCI

    W1GCI Ham Member QRZ Page

    Yes, W8JI's page is interesting and helpful. The burn marks on the choke in my 2100 are pretty much in the center as described. When I removed the choke and examined it closely, there's a blob of solder on the middle of the choke segment that appears to have been placed there intentionally - perhaps to shift the series resonance point to somewhere other than 26-27 mhz. When I removed the blob, the wire had been scraped at that point but the wires were not open anywhere. It also looks like the large coil in the output tank was squeezed perhaps to lower the frequency. I'm feeling pretty confident that at some point, this amp was "adjusted" to work on 11 meters. I'll rewind the damaged segment rather than the entire choke if I can and then ensure that the 10 meter setting will work at the correct frequencies.

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