--- In ham_amplifiers@..., R L Measures <r@...> wrote:
On Oct 22, 2006, at 7:39 AM, pentalab wrote:
#### any idiot knows you can't use Delrin rod as a form for a
roller inductor..
Oren Elliot mfg the roller inductor.
### well I guess Oren Elliot is an idiot then... so is MFJ. If
they had half a brain... they woulda known Delrin is a no-no. You
can tell it's Delrin from 8' away.... that stuff has a distinct
look about it.
.. and even if you didn't.... when u went to test
it for the 1st time... "in the lab".... it would melt in
front of
yours eyes ! They shoulda simply tested the prototype under
worst case condx... 1st.
900w into a "3000w" tuner is hardly a worst case, Jim.
### agreed. I meant to say... bring it up from 0-3500 W cxr...
with a high swr. IF it blows up b4 the 3500 w is reached... go
back to the drawing board. Point is... you rate a tuner for 3
kw... it had better handle 3kw. Now tuner's are used by hams
who have swr problems... and want the amp/gear happy. So 2- 3 kw
into a 3 or 5 to one swr would be normal. [for a tuner rated
at 3 kw.] If just a few guys ran 3 kw.... and a bunch more
2.5 kw.... and some rtty contest guys 1.5 kw... it had better
work... with some headroom. Ceramic... OR steatite OR Micarta
would have worked just fine..... so would thick wall hollow
teflon tubing. Delrin is dirt cheap... comes in rods... from
1/16" up to 16" Diam, solid. No wonder they used it. Beware,
some have used delrin for RFC's... then burnt the tops off...
most last forever....depends on a lot of factors.
[If u ran the lytics at the prescribed 75%
max V rating the manufacturer's recomend, they will NOT blow
up, if
the bleeder EQ resistor's open up.]
I'll bet a medium pizza with 5 toppings that I can show an
example where a 75% safety factor would cause a serious
problem if
a bleeder- R opened.
### U may well be correct
There goes the pizza.
IF the caps were badly mismatched in
UF to start with.
Not even with 1% matched.
### why is that??? Why wouldn't the V drop be proportional to
UF [One eq resistor open up... the rest intact}
.
### also.. My idea of adding a 2nd 100K resistor across each
cap is flawed.
Agreed. We have sold over 12k Matsushita, 3W, 100k-ohm MOF
resistors, so far there have been zero reported failures, and ther
is typically <0.3% variation in measured R in the same 1000-unit
box. .
### Excellent.... what is the max DC voltage rating on them ???
I'm guessing 450-500 V ?? Put 8 of em on an AL-1500, and u got
450 V per resistor right there.
If just one of the PAIR of resistors opened up.. the
V would skyrocket on that cap... regardless of the number of
caps in the string.
If there were two R-equalized caps in the string, V would
eventually double where one R opened.
## agreed. I'd say V would double ... asap...pronto. Perhaps u
should add a section on ur site... about NOT adding a 2nd
resistor per cap. The only justification for a 2nd string would
be.. if the 2nd string of resistor's were wired in series, nose
to tail... NOT connected ACROSS the lytics... but simply hooked
across the B+ and B- [ 1st and last cap]. This would decrease
bleed down time a bit... that's it. For an even faster bleed
down time.... 50 k or even 25 k resistors as a bleeder, NOT
eq resistor's could be added... or just 2-3 x big value wire
wounds. IMO, in that config... IF the wirewounds ever opened up,
u still got the eq resistor string.
### Back in my 4-1000 days... I'd just shut off the
HV..everyting else on.... and simply hit the PTT... say nothing, no
drive applied.... and when u go for idling current on the tube....
the idle current would suck the caps down to zero in a split
second. Of course, after they are discharged... IF u then
applied drive... the electrons would be attracted to the grid...
and u would wrap the grid meter around the peg. On this latest
project, the key line is routed through all the contactor's AUX
contacts... including the step start contactor's aux contacts...
so I can't key the amp with HV shut off.
In fact... that one cap would have DOUBLE the V
of the remaining intact caps/resistor's.
With 8 caps, opening one equalizer -R would eventually increase
the voltage at the open R's cap by 8x.
### why is that ?? With just one R per cap... and any one R
opened up... there should be NO current flowing in the remaining
7 x intact R's. With 2 x R's per cap.... and one of the 16 x
R's opened up... the cap with the open R would see exactly double
the V as the remaining 7. Where ar u getting this 8 x from ??
What am I missing here ??
IMO.. 1 x resistor per
cap... that's it. THEN, if any resistor let go... V would
divide according to each caps UF... with the caps with the
highest UF getting the most V.
Eventually there would be 0v on all the caps with intact
equalizer/ bleeder resistors and 100% of the voltage on the cap
with the open R.
### say what ?? Why would the cap with the open resistor
take 100% of the plate V ?? [1 x resistor per cap]
Of course the potential would never get there since electrolytics
tend to go BANG with not much of a surge in voltage.
### I'll bite. When one cap goes BANG.... does it blow open...
or short out? If it went open... no HV on remaining caps... if it
shorted out... then it's just plate V / remaining caps. in the
case of a L4B.. with 8 x 450 v caps.... even with 7 x
remaining... it's STILL only 378 V per cap. On an Ameritron
AL-1500.... with 7 x caps remaining.... it's 514 V per cap. Bye
bye Ameritron caps. They would blow up like firecracker's.
What's this secret administrator worried about...
Being fingered as a guy who can't stand to have his stuff
scrutinized.
threats, lynching's ? Perhaps he was 'appointed' by the
CIA..
or maybe Riley H himself ?
When he phoned me about retrofitting his 922, I found Riley
Hollingsworth to be a rather pleasant guy to converse with.
### Is Riley H gonna use his 922 for an IPA ?? We used to have
these local Radio inspector's, who were also active hams... back
in the 60's, 70's..... we called em... "the kilocycle cops". They
were a real piece of work.
later.... Jim VE7RF
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org
