Yaesu FL-2100B on 6 Metres?

[VK7MC]

Am looking for a modification to place the Yaesu FL-2100B on 6 metres?
The amplifier is similar in some respects to the Heath SB-200, same finals, same bands and I have found 2 consistent mods for this amp for 6 metres. The first is where the amplifier was gutted and rebuilt for 6 metres only, the other more popular modification was to loose 10 metres and modify this to 6 metres which is far easier and results in an amp that easily delivers 500W on 6 metres with 100W or less drive.

So why not the Yaesu FL-2100B I remember reading about placing this amp on 6 metres either in QST or AR maybe it was a mod via VK3OT? But I cannot find any reference now.... typical!

Mike
VK7MC

[VK2OMD]

So why not the Yaesu FL-2100B I remember reading about placing this amp on 6 metres either in QST or AR maybe it was a mod via VK3OT? But I cannot find any reference now.... typical!

Mike
VK7MC

Mike, I haven't tried such a change.

The FL2100B had stability problems. Yaesu tried to address the marketing problem with a half baked neutralisation scheme in the FL2100Z. If you look at the circuit, you will see why I refer to it as half baked and why it was a marketing solution rather than a true technical solution to the stability problems.

The stability issue might shape the way you want to modify it for 6m. I am not suggesting that you couldn't modify it to work stably on 6m, but you may need to incorporate effective neutralisation and the 2100Z is not a good example.

Owen

[VK5PJ]

Yikes,
this brings back bad memories . . .

Am looking for a modification to place the Yaesu FL-2100B on 6 metres?
The amplifier is similar in some respects to the Heath SB-200, same finals, same bands and I have found 2 consistent mods for this amp for 6 metres. The first is where the amplifier was gutted and rebuilt for 6 metres only, the other more popular modification was to loose 10 metres and modify this to 6 metres which is far easier and results in an amp that easily delivers 500W on 6 metres with 100W or less drive.

So why not the Yaesu FL-2100B I remember reading about placing this amp on 6 metres either in QST or AR maybe it was a mod via VK3OT? But I cannot find any reference now.... typical!

Mike
VK7MC

I tried this sort of conversion back in the late 1980's using a FL 2100B that had a burnt out band change switch (by default they work on 40mx like this) that I bought from a some one who had bought it in good faith. Any way, it sure did produce RF when you could keep it under control BUT it spent more than its share of time in self oscilation. I can tell you watching the tubes glowing a bright orange and the plate current meter hard over is not a nice way to pass time.

Mike, unless you have lots of time and god like patience to work out all the bugs, look for another way to generate high power RF on 50 MHz. I am not saying its impossible as you may have the golden touch but so far have not heard to many success stories.
I tried swamping the input circuit with a big resistor, a tuned input, and a very broadband transformer, all had their own good points but the result always seemed to be the same. A few different HT chokes, differing L C combinations in the tank CCT etc..

If you decide to proceed, please keep us informed as its nice to hear from others.

I eventually gutted the RF deck and put a single 8875 in there, while this was stable you had to wait for the warm up period unlike the 572B's that worked almost at once. I am guessing this amp is some where in VK5 hiding in a shack and is never turned on, sad really.

P.S if you have seen this amp let me know where it is at the moment