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Registered Member #2893
Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242
So I have this multiplier board and it's missing a cap on the final stage. The caps are 15kV 1nF.
I don't have a like cap but I do have a 2.2n 20kV one. My question is should I put it there, or should I move cap A to B and put the big one on the fist stage? I have 2 big caps so I could "balance" the first stage (replace the cap opposite A with a big one too). what would give the best performance?
Registered Member #1408
Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679
I have seen CW multipliers where such close proximity has lead to a problem. (sparking right through the body of the cap at that close a range). I would also consider a wax covering - as it MAY have been that puncture that lead to it's problem.
Registered Member #33
Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971
I recognize that board, it's from a Kodak/Trophy 2200 high frequency x-ray head, designed for operation at a few hundred kilohertz, with an output of 70kV 7mA for short duty use. It's a four stage multiplier, with pairs of caps and diodes in series. The diodes are <55ns Trr 16kV ones, I don't remember their current rating off the top of my head.
Since the capacitors are used in series, the higher value of the cap will not make very much of a difference, but the voltage sharing will be a bit off, so the original 1nF unit will see two thirds of the voltage, which is not ideal. A cap of identical value would be the best if you want to run it at close to full output voltage.
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CW multiplier cap...
