Yaesu FL2100B Linear twin 572B/T160L tubes 2.4 Kil


Ya`akov Nachum Miles:
I have a Yaesu FL2100B Linear with twin 527B/T160L tubes which have 2400 volts applied to the plate.  I am told by http://www.visradio.com that the Ameritron ARB-704i2 will interface this linear to my (solid-state) ICOM IC-706mkiig exciter.  I can't do this directly because the keying mechanism is different for the amplifier as opposed to the exciter, also the ALC voltage from the linear is waaaay too big for my solid-state exiter.  I have a spare set of Svetlana Russian 572B/T160L tubes.

This is an Avatar of the famous Heathkit SB200 Linear.  As I said there are 2400 volts on the plate, drooping a bit under load (voltage doubler circuit), and plate current about 450 milliamps at resonance, i.e. the legal limit on CW, the only mode I operate on HF.

Does anyone have any comments on the Yaesu FL2100B or the Heathkit SB200 amplifier?   I have used both a long time ago on 120 VAC, but it's been ages since I ran an amplifier...  I remember flattening the finals on the HeathKit SB200 Linear, and I remember that on the Yaesu FL2100B Linear there appeared to be rough tuning on 10 and 15 meters near the resonant dip - the current did not rise evenly on both sides of the dip on these bands.  Would this indicate a problem with parasitics?  Neutralization should not be required, as the Yaesu FL2100B Linear like the HeathKit SB200 Linear is grounded grid.

Steve Katz:
Of those two amps, and I've had and used them both many times, I'd choose the SB-200 over the FL-2100B.

The FL-2100B is a bit "cuter" to look at, but there are many things I never liked about it, including it having some strange failure modes (like the electronic bias board, which is overly complex and can occasionally blow up, quite literally).  It's also a bit undercooled, with those two tiny fans.

Both of these amps had high voltage relay keying, so you'd need an interface or a modification to use either one with the IC-706.  As for the ALC: I'm not sure what you mean by way too much voltage...it's adjustable, and as far as I can recall, it's adjustable down to "zero."  How could that be too much?


Delar Messmore:


If you had read your original post, we all told you essentially the same thing about the keying interface.

I'd take a Heath over a Yaesu anyday, anytime.

Parts are far, far, mor plentiful, and if you get a really sticky problem, the fact that the manual actually tells you how it went together from the ground up could be a big help.

I would think that there are far, far, more SB-200's in the world, than 2100 Yaesu's

Ya`akov Nachum Miles:
I am told what I need to interface my ICOM IC-706mkiig exiter to the Yaesu FL2100B linear is an Ameritron ARB-704i2 by http://www.visradio.com and have ordered one from them US$45 plus shipping.

Tom Rauch:
An uneven rise in grid current is indeed a sign of poor neutralization, and the FL-2100 has that problem.

GG amps DO sometimes require neutralization. 572's and 811A's are particularly bad tubes so far as having unwanted feedthrough power. Two 572's or 811A's in parallel are on the edge of needing neutralized at 30MHz.

Yeasu has a very poorly engineered feedback circuit, it is a capacitor beyond the tank that couples back to the input. Look at the schematic, and you will see what I mean.

I have something at:


73 Tom    


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