Hi Tim,How are you cooling your gap? Some of your symptoms suggest that your gap is overheating and failing to quench.
What are the details (manufacturer and part number) of the capacitors you're using in your MMC? Racing sparks can be caused by mistuning if your MMC is changing value during operation. This is usually not as much of a problem with self-healing capacitors until they approach their end of life.
How many are in each series string and number of strings in parallel?Are you using bleeder resistors across each cap in your strings? If so, what is the manufacturer and part number? Bleeder resistors not made for HV use may arc over or change value, messing up the performance of your MMC. This can usually be seen as flashes during operation, discoloration, or resistors even burning up. Some good, inexpensive HV film resistors include Vishay VR37 series or YAGEO HHV-50 series.
Bert Tim Flood wrote:
Thanks guys for the suggestions so far. The electrodes are not copper but 3/8" dia. steel round bar with tungsten carbide silver solder on one end so four pairs of flat round flats face each other. These steel rounds are mounted in aluminum blocks and are adjustable. It could be over time corrosion has developed over time between the steel and aluminum. I will disassemble and inspect this weekend. The caps that make up the MMC are new. They checked out OK individually and as a unit. Is it probable that a number of these caps could break down under load? Thanks again and I'm open to any ideas. Tim Flood On Thu, Mar 13, 2014 at 3:22 PM, W5als <w5als@xxxxxxxxx> wrote:Hi Tim This my opinion but I think the cap's are breaking down under load. I know they test Good but that doesn't mean they are. Just my thoughts. Alton Sent from my iPadOn Mar 13, 2014, at 1:54 PM, Tim Flood <tfloodrr@xxxxxxxxx> wrote: My old reliable coil's streamer length was gradually diminishing fromwhitelong sparks to shorter purple sparks and finally purple sparks for about ten seconds then no sparks. Additionally, racing arcs were beginning to occur. The MMC value checked out, all connections checked out, I cleaned and re-connected the dedicated RF ground, etc. The old design utilized two paralleled 9/60 NST, 3" dia. sec. and a3"x12"toroid with a spark gap consisting of four fixed gaps in series. I suspected the transformers so I replaced these with the only other oneIhad, a 15/30 NST. I ran the new transformer, required capacitance of.008ufalong with the existing secondary, spark gap and top load through JAVATC. Modifications were then made per the JAVA. The first light of the modified coil only produced a weak purple sparkwitha break-out point. Tuning only served to create racing arcs, with no improvement in performance. Now I suspect the secondary. So, I rewound and varnished the secondary. Same dismal performance as before. Now I'm about ready to loose it, tothepoint I'm explaining this all to my wife. The only thing I didn't touch was the spark gap and gap spacing. It wassetfor .030" for each of the four gaps and I made no adjustment when I switched transformers. Sorry for the long post, but I would really appreciate any ideas. Thank you, Tim Flood _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla_______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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