Ganged variable capacitor question
 

Dear all,
I am just taking my first small steps into homebrew and learning as
much as I can, but I have run into a problem that has me stumped. I'm
seeing some odd behavior with a variable air capacitor (first time I
have played with one of these), and have not been able to hunt down
anything relevant searching the net, so I am hoping someone out there
might be able to help me understand this. It is a 6 gang model with
sections of 120,150,20,30,90,and 30 pf. I was able to use a
continuity meter to work out the lugs, and found that the rotor is
continuous with the frame, and stator is isolated into 6 seperate
sections with no continuity between the rotor and stator. I assumed
that I could jump the stator lugs (none of which are continuous with
the rotor) with some copper wire to add up the gangs, but when I do
this the continuity meter tells me that the rotor and stator are
connected. It only happens to the gangs that I jump. I was expecting
continuity between the stator segments of the jumped gangs, but not
between the stator and rotor. Can anyone let me know if this is an
expected result, and if not suggest what I might be doing wrong?
Thanks in advance for your help.
Rusty.

Ganged variable capacitor question
 

Rusty,
That is an odd result...Are you certain that you don't have a stray wire
touching the frame somewhere?
If you measure an open from two gangs to the frame, and then jumper those
two gangs, measure a short, and then cut (not desolder) the wire connecting
them, are both stators still open with respect to the frame?
Are there trimmer capacitors connected from each gang to the frame (screws
with a thin mica insulator between the plates)? If so, perhaps you are
damaging them when you solder wires to the stator lugs. (Assuming you are
soldering).
Let us know how this comes out. Homebrewing is great.

Bob WB0POQ


wrote in message
...
Dear all,
I am just taking my first small steps into homebrew and learning as
much as I can, but I have run into a problem that has me stumped. I'm
seeing some odd behavior with a variable air capacitor (first time I
have played with one of these), and have not been able to hunt down
anything relevant searching the net, so I am hoping someone out there
might be able to help me understand this. It is a 6 gang model with
sections of 120,150,20,30,90,and 30 pf. I was able to use a
continuity meter to work out the lugs, and found that the rotor is
continuous with the frame, and stator is isolated into 6 seperate
sections with no continuity between the rotor and stator. I assumed
that I could jump the stator lugs (none of which are continuous with
the rotor) with some copper wire to add up the gangs, but when I do
this the continuity meter tells me that the rotor and stator are
connected. It only happens to the gangs that I jump. I was expecting
continuity between the stator segments of the jumped gangs, but not
between the stator and rotor. Can anyone let me know if this is an
expected result, and if not suggest what I might be doing wrong?
Thanks in advance for your help.
Rusty.

Ganged variable capacitor question
 

Bob,
I think I just sent you an email by mistake when I was trying to post
a reply (sorry about that). In case anyone else is interested, it
turns out that the suggestion to cut the wire instead of desoldering
led me to find that just heating the lug could recreate the short.
Apparently there is some solder on the inside of the capacitor that
caused the short after it melted when I was adding the jumper wire.
Desoldering the wire must have coincidentally reversed this. I was
able to heat and tap to get rid of the short and all seems to be
working now.
Thanks for the help,
Rusty.

Ganged variable capacitor question
 

On Dec 5, 11:52*pm, wrote:
Bob,
I think I just sent you an email by mistake when I was trying to post
a reply (sorry about that). *In case anyone else is interested, it
turns out that the suggestion to cut the wire instead of desoldering
led me to find that just heating the lug could recreate the short.
Apparently there is some solder on the inside of the capacitor that
caused the short after it melted when I was adding the jumper wire.
Desoldering the wire must have coincidentally reversed this. *I was
able to heat and tap to get rid of the short and all seems to be
working now.
Thanks for the help,
Rusty.

Good for you: A good find and good practice for looking for the
obvious and non-technical answer to a problem. Very interesting six
section capacitor!