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My MMC

Well, there it is. The cap consists of 12 strings in parallel with 22 series caps in each string.  The specs for an individual capacitor are as follows:

Manufacturer:        General Electric
Mfr. Number:        42L2152
Capacitance:          0.15 uF +/- 5%
Rated Voltage:       1200 VDC, 500 VAC

This is a detail view of the capacitors attached in a string with 10meg bleeder resistors.  I started with the #1 cap at the lower left hand side of the pic.  The lead on the back side (red line) bends up and to the right, while the lead from cap #2 bends down and to the left.  The two are soldered side by side.  Then on the visible side, the steps are repeated for cap #2 to #3 connection.  The string is repeated until the desired number of caps are attached.  Bleeder resistors are then attached between the paralleled leads on both sides.  This method has several advantages:  elimination of excess wire (hence induction) between caps, the leads are doubled for lower resistance, the caps are tightly packed, no PC board required.  On the down side, each of the cap leads has to be fairly precisely and equally trimmed (I made a small jig), same goes for resistors.  It's sometimes hard to hold two caps, solder, soldering iron and get the leads to line up...but I had over 300 caps to practice on!
 

Overall, putting each of the strings above in series, the cap would be .082uF and about 26,000 VAC using peak DC voltage equals peak AC voltage.  I think that by the time I consider all of the cutting and soldering time for not only the caps, but also on the bleeder resistors (not shown), this cap actually took more time than my corn oil cap.  BUT here is the catch:

This is a comparison between my homemade corn oil cap which has served very well in the past year and a half of service.  But consider the oil cap (left) is about .024 uF and is on the ragged edge with my 12KV transformer.  The MMC module in the center is .034 uF and easily handled the 12KV, even as I bumped the spark gap open a little.  The beer can is there for scale.  I'm only using a portion of the MMC because I'm still running with my 12 KV NST.  I plan to get a 9KV, 450 mA unit running by summer.  The new NST will use all .082 uF from 12 strings in parallel.