> >The protective choke opens when the HV is applied to it,
> >preventing HV to go all the way to your antenna.
>
> Faulty electronic circuit analysis. .
Yes, it sure was! I was on the tower all day...I should never send
a post when tired. Apparently, you did not read my correction.
The choke should be more robust than the breaker/fuses. It should
NEVER fail open when the HV appears across it, the breaker(s)
or fuses should pop first.
> >It is caused by one of two things....leaking/shorted plate block
> >capacitors, or some critter or conductive object shorted the
> >plate block cap out momentarily.
> >
> Such capacitors are not damaged by being shorted by a foreign object.
A short across the block cap from ANY source; animal, vegatable, or mineral
will apply Ep to the choke. How else can it get there? The choke is a long
way from any HV in the SB-1000. Measuring the block cap with an ohmmeter
is an exercise in futility. You need your famous hi-potter for this, or at least
the voltage the cap is rated at. In the SB-1000 et-al, the plate block cap is
way too small for the job... its not even a door knob.
What is the RF rating on the SB-1000 block cap, Rich?
> >I would change out the plate block cap(s) while you have the thing opened up.
> >
> If a ceramic plate blocking C does not indicate a short on an ohm-meter,
> changing it will have no effect whatsoever
It is obvious that the block cap is not permanently shorted. He has since fired
up the amp with the new RFC and it works fine. An ohmmeter is a waste of time.
If it is getting hot, it may have intermittant leak...it may not check bad at
ambient temp.
The bottom line is...SOMETHING put a voltage on the protective RFC that
was in excess of its rating. It had to be a foreign object or critter, or the
block
cap. I assume he cleaned out all critters and tools from the area before he
fired
up; so all that is left to suspect is the block cap.
I hope he used a replacement RFC that is more robust than the fuses this time!
We have discussed this before, Rich. HV where it is not expected to be is not
a good idea.
There was an on-going problem with the band switch on the SB-1000. There are
two types of SB-1000 owners; those who have had an arc on the switch, and those
who will do so if they work enough 80 meters. Ameritron improved the situation
by using mica padders instead of door knobs. It has nothing to do with VHF
parasitics. It is how the two tank coils are placed on the chassis, and the
placement
and use of the door knob padders. To get an arc that long on the band switch
takes a small Tesla coil, and that is what you have here. No other magic
involved.
Sorry for the confusion on my first post, guys. I knew what I wanted to say, but
it came out wrong.
(((73)))
Phil, K5PC
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