Yeasu FL-2100F schematic and or manual...

Discussion in 'Amateur Radio Amplifiers' started by K5ABB, Nov 4, 2017.

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  1. K5ABB

    K5ABB XML Subscriber QRZ Page

    Guys, I'm having some issues with my old Yeasu 2100F amp resonating when not under load... I thought the circuit was pretty much the same as the 2100B amp, but only without the 10 meter bits. I ordered the "kit from RF Parts to do the Yeasu recommended voltage doubler bias mod for the 2100B thinking it was the same circuit as the 2100f...

    Not so... the 2100F has an extra circuit board that 'LOOKS" a lot like the bias control board in the later 2100Z amp, but I'm not sure it's the same.

    BAMA has the documentation on the 2100B and 2100Z, but nothing for the 2100F

    In short, the only internet listing I can find for a 2100F manual (hopefully including a proper schematic) is, and they want me to download and install some software package of file converters on my computer. In short, I don't trust them at all, and ain't willing to risk it.

    Does anyone have a source for the 2100F manual I need?

    I'd be grateful for any help,

  2. W9GB

    W9GB Ham Member QRZ Page

    There were three variations of the Yaesu FL-2100 HF amplifier, that looked and for all practical purposes worked the same. The original FL2100, the FL2100B and the FL-2100F (Less 10 meter operation)
    USE the FL-2100B manual — noting missing 10 meter parts.
    EXTRA PC board — sounds like mod by earlier owner (illegal CB ?).

    Fox Tango has an entire web page devoted to Yaesu FL-series HF amplifiers.
    Carol Maher has instructions, parts list, and advice for radio amateur desiring to ADD 10 meters to their FL-2100F (becoming an FL-2100B). Junked FL-2100 amplifiers OR Amplifier Repair shops are one source for discontinued Yaesu parts. Amplifier Evolution.htm

    Yaesu Manuals — Entire Library here (current models, Yaesu USA)

    Carol Maher, W4CLM devoted hundreds of hours in compiling
    Yaesu information at FoxTango International Users Group, created 45+ years ago.

    Specific FL-2100F Questions?
    Facebook Group with Answers, Carol Maher is moderator.
    Last edited: Nov 5, 2017
    SM6CJB likes this.
  3. K5ABB

    K5ABB XML Subscriber QRZ Page

    Thanks for the reply, the PC board is definitely factory not home-brew or mod... Photos of 2100Z show what looks to be the same board, and the 2100Z schematic shows an additional PC board that looks to be the same, or at least very similar to the board in the 2100F. I'd just like to have the exact correct factory schematic for my amp as I try to sort out my oscillation issues.

    I'm familiar with the Fox Tango site, but they don't seem to have this manual there. They have the FL2000, and FL2500 series amps but surprisingly not the more common FL2100 series.
  4. G3YRO

    G3YRO Ham Member QRZ Page

    The Z version used a much more complex (but actually less successful) circuit for the bias and relay control. (don't see the point of this "voltage doubler bias mod kit"? The original circuit in the FL21000 works fine !)

    I worked on lots of FL2000B, FL2100 and FL2000B amps (all identical electrically) when they were current models, but have never seen an F version. So was this produced just for the USA, given your silly 10m regulations? If so, expect yours was a very late version, put together by Yaesu AFTER the Z version came out, using up old parts . . . but they fitted the same bias control board as in the Z.

    However . . . this shouldn't affect the normal operation of the Amplifier.

    What exactly is the problem you are having?

    Are you using Cetron or Chinese 572B valves? Both are fine, but these amps don't like the Russian 572Bs

    Roger G3YRO
    Last edited: Nov 7, 2017
  5. K6GB

    K6GB XML Subscriber QRZ Page

    2100F and 2100B are identical except for 10M.
  6. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    post nixed... cheers!
    Last edited: Nov 8, 2017
  7. K5ABB

    K5ABB XML Subscriber QRZ Page

    Thanks Roger, I'm running the Chinese made Taylor 572B's and they seem to be fine. I thought that the F model was in fact the same as the B model except without the 10 meter bits, and In many ways it is... The RF deck is identical, most of the input and output circuit are identical, but the grid biasing on my amp is DEFINITELY different from the 2100B schematics I have. It almost appears to be sort of a hybrid between the 2100B and 2100Z models.

    As for what's going on with it, the problem is that when the amp is idling under no load (unkeyed while receiving or tuning around) it will for no apparent reason, unexpectedly begin to oscillate on it's own, producing a strong local signal at whatever frequency the output tank circuit is tuned to as well as at least the second harmonic, and probably higher as well. When this happens the band scope lights up with the very broad loose signal, and the receiver noise level goes to S9 plus as it gets jammed by the rf signal from the amp.

    I can sometimes kill the oscillation with a tap of the cw key, briefly loading the circuit, but not always. I can also rotate the tuning control on the amp, seeming to pull the tank circuit out of resonance, and this will kill the resonance. It is said that the grid bias in this amp is insufficient to keep the triodes "shut down" while unloaded... there is also a well regarded line of thought (primarily W8JI) that believes this amp is very poorly neutralized as the neutralizing signal is pulled downstream from the final tank circuit, and consequently because of the tuned circuit the signal is NOT reliably 180 degrees out of phase from the input (it is anywhere from 50 to 150 degrees out according to W8JI). I can appreciate this in theory, but I'm NOT an engineer, so I can't really evaluate it independently and have to rely on those with more knowledge in circuit design than my own.

    In short, I like the amp, and when it runs properly without going into rodeo-like bucking fits, it's just what I need. I'm just trying to get control of the beasties' intermittent gremlins.

    Thanks for any help,

  8. N8VIL

    N8VIL Ham Member QRZ Page

    Check R201 and R202 at the back of the amp under the cover that covers the backside of the tube sockets. They should be 33 ohm 1 watt. If they are high or open, there may not be cutoff voltage getting to the tubes. In the picture they are the 2 identical resistors going to the tube sockets.

    16 Rebuilt input circuit.JPG 16 Rebuilt input circuit.JPG
  9. N8VIL

    N8VIL Ham Member QRZ Page

    I also sent a schematic to your email along with some other info. File was too large to share here.
  10. WA7PRC

    WA7PRC Ham Member QRZ Page

    The reason for the doubler is related to the greater gain of the later Chinese tubes. As is w/ Chinese tubes, the OE circuit doesn't supply quite enough cutoff bias. This can cause the amplifier to produce noise (oscillation) during stby/rcv.
    I redrew the FL2100B schematic in Visio and "printed" it to PDF. No matter how far you zoom in, the lines and text are SHARP, and every printout is a first-generation hard copy. Bonuses are, because I started with a vector drawing, text is searchable and the file size is tiny. I "printed" both A-size (8-1/2" x 11") and B-size (11" x 17") versions. :)

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