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

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

HI Chris,
           Am I to understand that you removed the original burnt
resistor and didn't replace it? If that is the case, the result you
got was a foregone conclusion.

Malcolm


On 26 Nov 2002, at 9:00, Tesla list wrote:

 > 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
 >
 >
 >