Re: THOR: SMPS warmup behaviour followup

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

Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "k= by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<Steve-at-g8cyerichmond.freeserve.co.uk>
> 
> My only experience of ferrite grinding was when I wanted to make the legs on
> an 'E' core equal (often the central leg is shorter than the other two, to
> make an air-gap). The method I used was similar to that used for grinding
> thin sections of minerals. Basically I used a thick glass plate, and a
> slurry of carborundum powder and a mixture of 50/50 water and glycerine.
> With the core held vertically I rubbed it face down in a figure of eight
> motion, rotating the core by 90degrees every so often. It was a slow
> process, I used the finest carborundum powder I could (from a local rock
> shop). Using coarser powder meant that I ground too fast and the results
> were very poor. It takes time and care, ferrite is very hard!!

	I have had good luck using wet or dry carborundum paper on a flat
surface,  with water as a lubricant.  It is less messy than the loose
powder, and you can get it in grades from at least as big as 60 to 600
or even finer.  Somewhere in this range will be the best value, as the
finer stuff serves more to polish than to remove much material.  The
figure 8 with careful handling is the way to go.

Ed