Dead MMC. was: AAAA! My coil...

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

Original poster: "Chris Roberts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <quezacotl_14000000000000-at-yahoo-dot-com>


Well, crud.

After reading the list posts and seeing that most everybody agreed on 
raising the resistors away from the perfboard, I raised the resistors off 
the perfboard by about 1/2 of an inch. I then put a small square of plywood 
underneath the one resistor that is in the spot that keeps getting blown, 
to better insulate it. I then fired it up. Instantaneously, there was a 
spark in that area, and I shut it down again. However, I noticed that the 
carbon mark was only on the top of the wood, not on the bottom or sides 
indicating an arc. I didn't pay much attention to it at first, and thinking 
it was solely the resistors fault, I took out the blasted one and didn't 
put in a new one. I figured the charge would just bleed into the other 
adajacent resistors. When the coil was fired up again, it worked okay for 
about 20 seconds, then a loud 'pop', and I recognized that special type of 
orange glow by the MMC. I rushed over, blew out the small fire, and took 
the coi! l in for the night. Rrrgh... there is a beautiful (sarcasm) black 
crater about 1/4 of an inch diameter in the top of the cap that the failed 
resistors were right underneath. So my coil is now declared dead untill we 
can get another cap.

However, since there was no evidence of an arc, and the cap failed seconds 
after I removed the resistor, and since every other cap and resistor are 
doing fine, could the problem be the cap? It might have been that the cap 
was shorting out, dumping the charge across the resistor, and when the 
resistor was removed it simply carried the current itself and blew up. Any 
ideas?

Also, (sorry about so many questions) someone told me that with 2 strings 
of 6 geek caps, the mmc is not suited to handle the voltages at the peak 
voltage. (9000VAC r.m.s. voltage, much higher peak voltage) however, the 
geek group recommended the current setup, so am I okay as is or do I need 
to redo my mmc completly? (I thought I was doing fine, now I'm confused 
again). Thanks.


-Chris