Re: 811a coil/ bad diode?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Steven Ward by way of Terry Fritz <twftesla-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>

I bought a new diode, you guys are all right, my diode was good all along.  
Oh well, my next suspect is my tuning capacitor (across primary coil).  It 
gets pretty hot, so i need to upgrade.  Anyone have any suggestions??

Steve Ward.


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: 811a coil/ bad diode?
>Date: Thu, 04 Jul 2002 23:27:59 -0600
>
>Original poster: "S & J Young by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><youngs-at-konnections-dot-net>
>
>Steve,
>
>Yes, Microwave oven diodes are different in that they are a bunch of diodes
>in series.  The typical forward voltage drop across one is six to 8 volts.
>Usually, this is more than the voltage used in your ohmmeter, so it will
>indicate an open circuit even though the diode may be perfectly good.
>
>To test the diode, use a couple of 9 volt batteries in series, or a 12 to 
>18
>volt DC wall wart, connect it to the diode and a 100 or so ohm resistor in
>series.  Measure the voltage across the resistor.  Depending on the 
>polarity
>of the diode, you will measure either zero volts, or supply voltage minus
>about 6 or so volts if the diode is good.  If you measure zero volts for
>each polarity of the diode, it is blown open.  If you measure the supply
>voltage across the resistor, then the diode is shorted.
>
>--Steve Young
>
>----- Original Message -----
>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: <tesla-at-pupman-dot-com>
>Sent: Thursday, July 04, 2002 12:52 PM
>Subject: 811a coil/ bad diode?
>
>
> > Original poster: "Steven Ward by way of Terry Fritz 
><twftesla-at-qwest-dot-net>"
><srward16-at-hotmail-dot-com>
> >
> > Hi group,
> >
> > I think that i may have come across my problem with my small VTTC that 
>ive
> > been working at for awhile.  I decided to check out all of my components
> > today and found that my diode is not testing good.  It reads open 
>circuit
>in
> > both directions.  Is this a sign of a bad diode?  I know that it would
> > usually be, but are microwave diodes different?  Another diode 
>(suspected
> > bad as well) i have reads 4kohm im both directions.  I think i may have
> > blown the diode when someone on this board told me that the schematic 
>was
> > incorrect.  I followed his directions, and blew a 15A fuse, and was
>probably
> > quite close to blowing my tube! im sure that amount of power could 
>destroy
> > that little diode.  So i followed the original plans and the coil works 
>OK
> > giving about 3" sparks at most, with unopredictable performace from time
>to
> > time. Ive been running the coil for a few days with out realising my 
>diose
> > may be bad.  This makes me suspect the diode.  So do i need a diode?  or
>can
> > i bypass it?  a new diode isnt much of a problem but i want to know it i
> > even need it, and if i dont what other modifications do i need to make?
> > Thanks,
> >
> > Steve Ward.
> >
> >
> >
> >