On Sep 25, 2:50 pm, Edd Whatley
wrote:
If you have ever torn down a paper / mylar / poly capacitor to view its
internal infrastructure, you would see the offsetting of the dielectric
foil upon the dielectric separator and the clustering of the mass at
both ends . That then needs to be collectively interfaced to the two
wire connector leads. That is usually accomplished by a pressure
compression of lots of surface contacting area or a enclosed crimping
action and the other means being via a large molten solder "blob" which
will properly meld with the tinnable copper wire lead and be dependent
upon the other contact aspect to be the extensive area of foil that has
solder interspersed within it.

Now getting to your special feature of the "safety capacitor".
You will be finding it placed in the collector / to / flyback primary
winding where it is resonating
along with the primary of that transformer, as that transformer action
certainly is more efficient operating as handling a pseudo-sine wave
versus a positive polarity sawtooth waveform.
With that resonance established between the two components of that
tuned circuit , there will be
quite a degree of flywheel energy present and an actual lowered degree
of required power required
as compared to a circuit with out that aspect being present.

Now lets look at that repetitive 15,734 ~ signal that is continually
hitting that current loop in the hoz output stage, much in the order of
an instantaneous power impact effect of a jackhammer.
If all is well in the hoz circuit, fine, no problems will be
had.......but lets move back to the described capacitors internal
structuring , if those high current pulse might find a weak / marginal
contact area within that cap, expect it to arc over, vaporize metal
and open a portion of a previously contacting area. That then leaves
progressively less area to be carrying and sharing the current
requirement.

A daisy chain or domino effect is then possible with the eventual loss
of all contact area made to the foil and either arc over or loss of
internal contact completely and the loss of connection and capacitance
transfer.
Now IF that cap is effectively out of the circuit, by virtue of that
opened internal connection.
Expect that previous effect of drawing less current while being in
coincident or close to resonance state to the frequency that the hoz
power circuitry was operating at, to no longer be valid.
The power consumption...i.e. current passing through that loop should
increase, along with a shooting up of the high voltage level being
produced at the fly /IHVT output by virtue of being hit by the sharp
peak of a sawtooth waveform now.
That would be limit taxing on the HV components as well as possibly
getting up into the X-ray level from picture tubes, or even up to the
ultimate threshold of actually breaking the kine via a circular ring
fracture about the yoke mounting area.
That is where the safety aspect of the mentioned capacitor comes into
play.
In examining the circuitry, you will find that the caps dual leads are
dependent upon completing specific interconnections.
That being in the closed loop from the B+ supply to the collector
circuit of the Hoz output transistor. Within those capacitors, there
are internal fusible links between adjunct leads, such that when
operated beyond their current passage design center, an opening will
occur internally, opening their circuit, such that the sweep circuit
then becomes disabled.
Therefore being dubbed "safety capacitors", so that extreme condition
never occurs, or merely rising upon that threshold for an instant.

Regards..... Edd

--
Edd Whatley

That is really an interesting discussion of how these things work. But
it begs the question of why didn't they simply put some type of fuse
or fusible link in the circuit? Lenny