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Re: [TCML] Re: Terry Filter Caps Suffering From Early Death

Scott -
   
  Gary Lau is absolutely right: your Terry filter is seriously mis-wired.
   
  Looking at the bottom of the board,  you have jumper wires connected directly across each of the four center resistors on each "leg" of the filter. Since your capacitors are also connected in parallel with the resistors, none of these components are actually "in circuit"; they are all just bypassed by the jumper wires.
   
  Only the two "end" capacitors in each string are actually "in circuit". So, each leg of your filter has only two series-connected capacitors, providing a "rated" voltage of 3200 VDC for the 2-capacitor string.
   
  Since you are now using a 15KV NST, each "leg" of the terry filter is seeing 7.5 KV (or even more, if you are using a variac to boost NST input voltage)..  Cap rating is 3200 volts, applied voltage is 7500 (or more), failure is to be expected.  So, even though these capacitors have some safety factor as far as voltage rating, applying MORE than 2X their rated voltage WILL result in rapid failure.
   
  (Terry Fritz did some test-to-destruction evaluations on these caps when he was first developing his R-C filter design, but the Hot-Streamer website seems to be down right now and I can't determine what the actual breakdown voltage was for these caps.)
   
  Regards,
  Herr Zapp
  

Scott <doxiescott@xxxxxxxxx> wrote:
  UPDATE:
Here are some high resolution prictures of the filter.

Top View:
http://img179.imageshack.us/img179/6770/p6160571md0.jpg

Bottom view with connections outlined:
http://img179.imageshack.us/img179/9494/p6160577zm4.jpg

And a mug shot of the two suspects:
http://img179.imageshack.us/img179/5586/p6160579tq5.jpg

For some reason, my meter isn't giving me a reading on the resistors,
even in the appropriate 2000k setting, although after charging a cap
and hooking one up, they seem to do their job...interesting.

Hopefully these pictures should help, thanks to everyone so far.
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