FL-2100F Continued

Discussion in 'Amateur Radio Amplifiers' started by K6GB, Jul 28, 2018.

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  1. G3YRO

    G3YRO Ham Member QRZ Page

    Just because you can't find any figures for the RF current and voltage ratings of the RDA capacitors, doesn't mean they aren't suitably rated.

    The bottom line is that clearly Yaesu and Kenwood chose them because they knew they were suitable, either because they had the figures from the suppliers, OR they tested them themselves. They had reputations to maintain, and certainly would not have chosen sub-standard components back in those days. (you only have to look at the standard of parts chosen for the original FT101 series to see that quality was more important than cost, unlike later rigs like the FT101Z)

    Furthermore. when used as padders on the lower bands, if their capacity changed with RF, the tuning would alter - but it DOESN'T . . . so clearly they are suitable, even in the much higher power TL-922 amplifier.

    As stated before, I've NEVER seen any of these fail in an FL2100, not while I was working for Yaesu, nor in any of the Amps I've serviced in the all the years since, nor in my own FL2000B used regularly for 40 years!

    I can only summise the ones YOU have seen fail have been down to mis-use / operator error, but NOT unsuitability for the job. (if they weren't properly rated, THOUSANDS would have failed !)

    Roger G3YRO
     
  2. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    No need to argue about it, but I've seen quite a number of these fail. Owned by hams, purchased new, not abused as far as I know.

    An article from the Netherlands discusses this...

    FL-2100 capacitor failures.PNG

    Is the "legal limit" in the U.K. still 400W output power? (I remember it always used to be, but haven't really refreshed this information.)

    If so, and hams are actually operating lawfully, then they might be using FL-2100s at about 2/3 output power, which would be easier on everything; and they'd be using TL-922s at about 1/3 power, even easier on everything.

    I've also repaired a number of TL-922s over the years and have encountered many of the same things Tom W8JI found, which are discussed here, along with "fixes" to make the amp more reliable and more stable: https://www.w8ji.com/tl922_mods_parasitic.htm

    More mods and improvements from PA0FRI: https://pa0fri.home.xs4all.nl/Lineairs/TL922/tl-922eng.htm
     
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Well the Dutch article you posted suggested the capacitors failed due to overheating . . . which is what I said originally!

    I doubt if anyone who owns a Linear Amp over here runs it at 400W output ! So I doubt if that's the reason . . . I just think it's people using them PROPERLY.

    The only mod I have done to my TL-922 is directly ground the grids . . . haven't done anything else as it seems perfectly fine ! (although I do turn it on via a simple manual soft-start switch in the mains lead)

    Roger G3YRO
     
    Last edited: Aug 10, 2018
  4. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    You're doing okay.

    I've seen TL-922s exhibit a parasitic oscillation around 120 MHz many times; even with grids directly grounded (although that does help).

    It's a beautiful, nicely constructed amplifier but it has its design weaknesses. Inrush current was obviously one of them (like the Kenwood engineers never bothered to measure that).

    Amps I've found with really no design weaknesses I could find, which is probably why so many are still working fine after 40+ years with zero modifications of any kind, were made by Henry and Alpha. The Henry 4K Ultra is probably the best-designed amateur amplifier I've ever seen, used or owned. Geesh, they thought of everything. But it weighs 190 lbs and was very expensive. They even metered PA filament voltage, and you could adjust it without opening anything (although the Collins 30S-1 also did this, even earlier).

    Same guy who designed that left Henry and runs his own company now, ASI, which is about two miles from me. They mostly make "BIG" amplifiers, but will still make amateur ones to order. ("BIG" as in 50kW stuff.)

    Charlie's a great amp designer. He's of the old-school of thought: "You have to hammer it until it breaks, then fix it, upgrade the design and hammer it more, and keep doing that until you can't break it."
     
  5. N8VIL

    N8VIL Ham Member QRZ Page

    Funny you bring up the CB angle as I was thinking that. Some of the Yaesu amplifiers I repaired that had bad doorknob capacitors and looked like they were run hard. Some also had burnt plate chokes and some with the 10 meter coil tap moved that had to be corrected. One had a RF sense keying circuit installed. Maybee more defective amplifiers here in the states because they were in the wrong hands.
     
  6. G3YRO

    G3YRO Ham Member QRZ Page

    Exactly ! In the hands of people who don't know how to use them properly, ANY Amplifier will fail.

    And running an SSB Amplifier on high power AM would simply cook everything !

    Hey, I'm not saying the FL2100 amplifiers are perfect . . . ANY piece of electronic equipment can usually be improved with minor modifications . . . but generally speaking, when used properly I have found them to be very solid and reliable amplifiers.

    You have to remember that Heathkit equipment was extremely rare over here . . . there were probably 1000 times more FL2000Bs & FL2100s than SB200s sold here in Britain . . . and other Amps like Dentron etc were also very rare.

    Roger G3YRO
     
    Last edited: Aug 10, 2018
  7. K6GB

    K6GB XML Subscriber QRZ Page

    Installed a new plate cap, Jennings from RF Parts, the old one was way out of spec only about 200pf. Was bringing it up and was going ok then something popped, no time to look at it today, but input swr on 20m is still way high, best I can get is 3:1, I think I may have a bad switch, I replaced the cap, the old one was bad.
     
  8. G3YRO

    G3YRO Ham Member QRZ Page

    Presume you are talking about the ceramic OUTPUT switch? You should be able to SEE if the switch is OK . . .

    If it has burnt out (and dissolved some of the metal) that will be pretty obvious on close inspection.

    Again, these are pretty decent switches . . . they only fail due to mis-use. (but I have replaced a few)

    Worth inspecting the Input switch section too, at the back (not so easy to see, but can be checked with a multimeter)

    Roger G3YRO
     
  9. K6GB

    K6GB XML Subscriber QRZ Page

    No, I'm talking the input switch, but I'm going to rest it for a couple of days. The output switch looks ok. I think someone has taken the golden screwdriver to this, and I don't think it was the "Doctor".
     
  10. WB2WIK

    WB2WIK Premium Subscriber QRZ Page

    Sounds like you're spending time and resources on an old amp.:)

    Might have been easier and cheaper to just buy a used AL-80B, which runs more power and is a very solid design.

    But fixing stuff can be fun and educational, for sure!
     

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