Carl, if semi floating the grids with caps..on a GG triode is such a wonderful
idea, then how come you will
NEVER see it done with tubes like 8877, 3CX-3000A7, 3CX-6000A7 and YC-156,
YC-172, GS-35B ??
You don’t even require a suppressor with the above tubes. No trade secret
hush-hush top secret KM1H designed
suppressors required.
IMO, you gotta be nuts to use grid caps + chokes on any 3-500Z amp. Besides,
with the grids bonded to chassis
with wide cu strap on any SB-220, SB-221, TL-922, L4B, henry amp etc, you
can now stuff 4-400A/B/C tubes in there
and they run just fine. The grid chokes on any L4B amp is not gonna make for
a good grid fuse any time soon, it can’t.
The grid choke on a L4B is only .9 ohm vs the 25 ohms on a SB-220.
A simple, fast HV fuse wired in front of a 50 ohm glitch resistor..and both
wired into the B+ takes care of any anode to grid flashovers,
blows open in less than 2 msecs. 50 ohm glitch R limits the peak fault
current, and the HV fuse interrupts the peak fault current.
2nd fast HV fuse, wired between either sec of plate xfmr and FWB, protects the
FWB + xfmr, in cases where a short occurs prior to the glitch resistor.
A simple rear mount 3agc fuse holder, bayonet type, + fast grid fuse, makes
grid protection easy on any directly heated,
thoriated tungsten tube. ( wired between chassis + neg terminal of the grid
meter..or grid shunt).
With 8877, YC-156, and any other indirectly heated, oxide typ tube, electronic
protection is required.
For a HB 6m amp, even if I had a case load of new chinese 572B tubes.... I
still would not use em. Sure they will work, but are a poor
choice for a 6m GG amp. A SINGLE GS35B on 6m, will easily run quadruple
the power of one of your SB-200 6m conversions......and no suppressor
required on the GS-35B ! This has got nothing to do with running high power
with bigger metal tubes either. It’s a simple case of using the right tube
for the job. The SB-200 came out in 1964. It’s now 2013, get with the
program.
later.... Jim VE7RF
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|