can some one look something up for me?

[N3DRB The Derb]

I'd just love to know what the G-P capacity of 4 811A's or 4 572B's is... in other words, what range of neutralizing cap I would need to put into the Gonsets using traditional methods as opposed to Gonset's "preset" metal bracket with a wire wound around one of the fil chokes going to ground? I'm not impressed.

believe I'd rather do it with a real cap. Recommendations? assume 2000 volts on the finals. needs to be small and adjustable from the side of the amp using long non conductive screwdriver.

[W3RSW]

The interelectrode cap's for 811A's and 572B's are almost the same.

C-in, 5.9 and 5.6 pf respectively.
C-gp, 5.6 and 5.9 pf,   "
C-out,  0.7 and 0.9 pf, "

So multiply all by 4 for 4 tubes.

Unlike screen grid tubes which have small C-gp's, C-gp's for triodes are comparatively large, about 10 times. They don't have screen "shielding" between the grid and plate.

I assume your running grounded grid so you really don't need a whole lot of neutralization anyway. But if your planning on rewiring for Class C, and if the plate circuit is a pi net output then the grid circuit must be a balanced input coil /cap combo to get the necessary neutralization pick off.  Pi nets normally can't be used in both input and output in a grid driven triode circuit since there's no way to get neutralization  (-normally, I guess Gonset cobbled something.)

[WA1GFZ]

Rick Measures told me not pratical to do in a GG linear....

[N3DRB The Derb]

Hmm the neutro adjustment on the gonset is a rather large piece of steel sitting on top of a ceramic feedthru, which is "preset" so they claimed, and "does not require adjustment even when changing tubes." ( direct quote ). It sits up near the tube plates.  the bottom side of the insulator connects with a small solid wire wound over the top of one of the fil chokes (I think in the reverse direction but I gotta look at it again) with the far end soldered to chassis ground.

of course there's no way to know if it has ever been "un-preset" by someone. Were there not some Heathkits or something else that used something similar?

I'm about ready to by pass the #@*^&%$!(&#%$ band-switch  and just hook it up for 75 and nothin else. But I gotta fix the tuna first. In between cooking dinna I am jig sawing new input coil supports out of the acrylic Slab gave me. I believe this stuff is going to stick good this time. looks kewl too. Frosted gray color. 

[Opcom]

I'm confused a little. Why does a GG amp have to be neutralized? I never seen an unstable one. luck?

[N3DRB The Derb]

I'm not sure . There were some other amps that did have some neutro scheme of some kind, but the names escape me. Might have been the Hunter Bandit amp, which I think also used 572B's.

I'm still thinking class C on some tech matters and of course things are way different.  I still dont know if the Gonset problems are due to parasitics or just a wimpy assed bandswitch, or a combo of the 2.

I know there were some 100 watt class rigs that had a metal bracket like his thing does. 

[The Slab Bacon]

I have never seen a GG amp but the gonshit with a neutralizing circuit. Typically they dont need it by the nature of the beast. First of all the input Z is low enough to make them somewhat immune to feedback, and the grid(s) tied to ground also somewhat creates a shield between the input and output. Also having the grid grounded also breaks up the tubes interelectrode capacitance and internal feedback path.

FWIW, I wouldnt wast a lot of time and effort coming up with a neutralizing circuit for a GG amp unless I found that it really needed it. Careful component choice and layout should make it unnecessary. (IMHO)

                                                              The Slab Bacon

[W3RSW]

Which makes one wonder all the more why Gonset put one in; surely they wouldn't waste money on an insulator, piece of wire and plate of steel for a sales pitch.; er.... would they? 

Maybe by magic they got one of the unstable prototypes to work by fauxing up some sort of neut. circuit and manufactured all the rest that way.

Yeah, that sure is one heck of a wimpy bandswitch too.

[W7IXZ]

The Heathkit HA-10 Warrier used a neutralizing circuit as well.  It ran 4 811A tubes.  The circuit was similar to what you were describing.

Larry W7IXZ

[w4bfs]

likewise the B&W lk1000 with 2 813 gg ...design for the amp came straight from lighthouse larry (or visey versey) stub neutz and mystery 50 pf cap...73 John

[N3DRB The Derb]

I totally went through Richard Measures material today - printed off 50++ pages and read all of them while I sat down at the wifey workplace. I developed the following attack plan:

I think he has it right and I am going to order his suppressor kits. 1 for each amp. He supplies everyhing you need in one shot, and I don't wanna waste time trying to find everything myself.

 I am also going to replace every single 'fingered'  switch contact with a solid one that has no thin ' finger ' areas, and I am going to double the number of poles on each section and wire them all in parallel using short bus bar wire. I'm also going to be ordering the silver plating kit I talked about in another thread some time back and use that to silver plate anything I think would be better off getting a fresh dose. At 30 bucks it's cheap enuff.

my prime suspect in all this trouble is the 5"+ flat ribbon going from the plate blocking cap sitting on top of the plate choke to the plate tuning cap. Looks like a dandy little vhf strip-line to me. If I double the contacts and the poles, the bandswitch may be no longer an issue.

I sawed out 20+ coil supports last night for the tuner, I need to go in there and start epoxying them in place. I also have 2
complete electrolytic replacement kits to install in both Yaesu's, and Yaesu #2 still needs the power board wired in and test for transmit.

[W3DBB]

.

[WD8BIL]

811As at their high end plate voltage operation tend to take off in the 20 to 23Mhz range.

[KB2WIG]

 "I know there were some 100 watt class rigs that had a metal bracket like his thing does.  "

Sounds painfull.

[N3DRB The Derb]

amp worked like a champ until you dropped the HV maul down and went from tune to operate. Instant burned up contacts and zottage after that.

The cool thing about having problems is how much you learn and re-learn when you go about solving them. I am going to make these amps work for me, because of what they represent, you know. Nobody else cares about em, but I'm going to master them before I'm thru. No 'collector' value whatsoever. Just fun value, as Slab put it.  Just what I like. 

Ham radio is a lot more fun when you take the money considerations out of it. You can do exactly whatever you like to do.

[Rick K5IAR]

Well put, Derb!  It is simply amazing how much one can learn from troubleshooting and repair.  Besides, it's FUN! 

Rick

[N3DRB The Derb]

I'm gonna do all further testing with the 572B's.  Right now I'm working on the Matchbox again so I can get back on.  Heres the
rough coil support bars clamped down ready for sanding even and straight. One of these on each side supporting a smaller one sitting in the notched out sections. Supported on all sides. No possible way to break.  #8 solid wire.

[KA2PYQ]

Even in the changing environment of changing bands so changing
neutralization so it is that it needs changed neutralization, or is it,
the neutralization problem you may be having might be an effect
on many frequencies at the same time as a sort of chorus, not
necessarily the fundamental, so how about trying some of the
"non neutralizing" ways of getting rid of the parasitics first:
Put a 27 ohm 1- watt resistor in series with each plate shunted by
3 turns of wire. or, since grounded grid, the same with a whole
bunch of 15 ohm resistors (mechanically radially) in parallel with
each other and between grid and ground.
Also look out for trouble RF chokes that need to be inside of
shields or changed value.

[W1EUJ]

Word salad.

[KA2PYQ]

Well I tried (anyway it`s right). It`s better and easier to ask and
answer this question on the air. As far as I`m concerned, that`s
Ham Radio or WBCQ.