[Test-Equipment] door knob caps

[Mike Manes]

Depends on the dielectric.  "Doorknob" describes a package, but not
necessarily the dielectric.  Mica dielectric can handle substantial
RF current compared to Z5U ceramic.  A TV set HV cap sees mainly DC
with some 16 kc ripple, and so is likely to be ceramic.  This is why
I recommended gradually increasing the cap RF current while checking
for heating.

73 de Mike W5VSI

Bob Roehrig wrote:
> On Mon, 23 Jul 2007, WB6BLV  Central California wrote:
> 
>> Not sure why the warning bout not using these caps in tuned circuits 
>> or as
>> bypass or feedthrough as I have used them in QRO amps for decades with no
>> difficulties whatsoever.  If the capacitance measures close to the marked
>> value they are almost always OK.  I have never had one go bad nor have 
>> I had
>> one turn out to be bad if it measured as marked in capacitance.  Just my
>> $.02...
> 
> OK JOhn. Well that at least was my experience with them. I can't 
> remember but I think I tried one 500pf unit across a variable cap in a 
> transmitter tank and it went "poof". Now this was a pullout from a TV 
> set, rated at 20KV.  I know the Centralab ceramic units that kind of 
> look like doorknobs are just fine. I'd be interested in knowing what 
> luck others have had with the standard TV doorknobs.
> 
> 
>                               Bob Roehrig
>                     Aurora University    Telecom dept.
>                            broehrig at aurora.edu
>                          K9EUI  W9ZGP  WD2XSH/19
>                     630-844-4898      fax 630-844-4222
>                     "Nostalgia is a thing of the past"
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-- 
Mike Manes    manes at attglobal.net     Tel: 303-979-4899
"Things should be made as simple as possible, but not more so."  A. Einstein