--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@...> wrote:
TONY SEZ.. And that still takes us to electronic protection...
### My concern with electronic protection is.... if it
malfunctions... when u need it ! I have seen these high energy
diverter's.. [used to crow bar HV supplies, used in commercial
large HV supplies like John Lyles describes at times]
malfunction.... then u have the charred remains of a huge diode
stack !
### Having said that... it would be simple to incorporate two
of everything... redundant protection schemes... and
incorporate "test switches" on em..... so u can actually test em
on site... without having to drive ur expensive tube into 'too
much plate + grid current'
### I have looked at both triode boards in the past. Some of it
would need extensive mods, etc.
But the price is nominal for them... use the pieces you need. Take
a little time looking at Paul Hewitt's board (WD7S). He has done
some nice work and all his trimmers are multi turn pots.
## agreed. He did have one UNIQUE twist. His board would sense
the HV [ I think from the HV multiplier resistor's] and if NO
hv present.... would inhibit the T/R relay's......very slick.
### IF my HV fuses blow... the amp is still online, being
driven.... and a split second later, the grid fuse blows. His
scheme would keep it shut down... until the HV was XXX volts.
TONY SEZ .. Paul does do some neat sensing and comparing input and
output. worth looking at!
### I'm gonna check his site again. I really don't like the SS
relays in the 240 V primary. To work right... they should be zero
cross Voltage on turn on.... and zero CURRENT cross on shut
down. The 80 A rated ones I have seen require aprx a 100+
square inches of aluminium plate [very thick].. as the heatsink.
They also have leakage across em. In Canada, they can't be used as
the sole disconnect... they gotta be supplemented by at least a
fuse. My electrician buddy got zapped last yr from one... from the
leakage.
### Like u say.... the SS relays/ mech relays in the primary are a
poor way to go, to shut off ... "follow on energy".... and totally
useless to eliminate the B+ energy stored in a bank of lytics.
### Come glitch time, the idea of opening up the primary 240 V
with a SS device freaks me out... ditto with a contactor... even a
big one. Notice on the backs of 240 V breakers .. like the
P+B "controlled magnetic hydraulic breakers" [ these things are
500% better/faster than any standard heat activated breaker] they
all have slots on the rear. My buddy sez they are... 'arc chutes'
designed to divert the arc out the back.. and away from the
contacts. Most breakers will have a Max KA interupt rating on
em... like 100 ka, most are designed to handle a dead short....
and assume the supply line from the street WILL pump out a huge
amount of fault current.
### Even the fast breakers in the 240 primary are not fast enough
during a glitch. To eliminate the "follow on energy" from the
xfmr + diodes + caps..... I used the pair of sandfilled HV
fuses. 7900V /50 ohm glitch R = 160 A 160A flowing
through a 3 A rated HV sandfilled fuse blows extremely fast...
and quenches the arc asap... as the sand turns to glass!! The
other reason the fuses are filled with sand is to void 95% of the
air inside the fuse to begin with. [little or no air left to ionize]
### The 100 A breaker in the 240 V line always remains intact...
the faster fuses always beat it to the punch.
Love reading your technical details!
### Tnx.... none of it is rocket science... just a lot of
experimenting over the yrs... and bumbling through things. I still
contend.. most of this stuff coulda been done at least 30 yrs ago.
### My buddy phones me last night in an uproar... his 15 kw
linear is putting out zero watts... and input swr has
risen........ turns out it was the grid fuse gone open...... from
the day b4.... when he just about vapourized his 15 m ant !
### QRO is one thing..... ALL this stuff downstream is another.
His 160m GP has a 30 ohm Z..[his mfj shows 1.7:1 swr right at
the feed point.] He wants to use a 4:1 balun on it... using a T-
200 core !! ["to match it"] The simple solution was to use an L
network... minus the cap of course. A simple 4.9 uh coil
hooked directly across the feedpoint coax resulted in a flat swr.
F-12 calls it a hairpin... Hy-gain calls it a beta match. It works
on yagi's..... and now it also works on verticals + Groundplanes....
simple... one component. Now we remove the temp 12 ga 4.9 uh
coil.... and replace it with a permanent 1/4" OD copper tubing
coil....nothing to blow up.... end of problem..... end of story.
Later... Jim VE7RF
73, Tony W4ZT
