Hey Stephen...Most of the older model NST's have "surface" cracks in the tar but this doesnt mean that the cracks propigate to the trannie area. If you are getting good preformance from both outputs to a ground, then I wouldnt worry about its insulative properties. when reheating the "tar", you can cuase some leaks to form around the exit points of the insulators ( due to overheating the rubber rings/seals) .
when reheating an NST to reset the tar can be a slow and tedious process. If you heat it too much, you can introduce extra gas bubbles in the tar that will become a problem after it has cooled... the cooling process has got to be a slow steady situation to avoid "sinkage" ( as seen in parafin applications) .
you need to heat the NST to a point as to where there is no or minimal smoke coming off of the tar... best bet is to never place the NST directly over the flame but off to the side and put the lid into place to retain the heat from the charcoal. This can take several hours depending on the heat trapped in the BBQ grill...
Scot D Stephen J. Hobley wrote:
I got hold of a 12kv 60ma NST from a local sign company. It's pretty old and the potting is a bit cracked, as you can see: http://www.flickr.com/photos/20929480@N03/sets/72157607383559345/ It passes the "arc to case" test on both sides without any issues, but I was wondering if I should repot/remelt this? I almost cranked up the grill, but then I read how you can overcook the potting on towards the base if not careful. I did melt some of the bigger cracks closed with my 'pocket blowtorch'. Steve _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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