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Re: Death & rebuilding of a Neon




From: 	Gary Lau  01-Dec-1997 1352[SMTP:lau-at-hdecad.ENET.dec-dot-com]
Sent: 	Monday, December 01, 1997 12:05 PM
To: 	tesla-at-pupman-dot-com
Cc: 	lau-at-hdecad.ENET.dec-dot-com
Subject: 	Death & rebuilding of a Neon

After obsessing over optimal transformer protection network, saturating
chokes, and the like for many posts, I fired up my coil last week.  I
cranked the variac up to maybe 25%, had good spark breakout, but the
safety gaps were firing almost continuously.  This was strange, it had
previously been working at 100% variac just fine, I know it was tuned.  I
observed this for maybe 5 seconds, then a dreadful silence.  Post mortem:
a dead 15KV/60mA neon transformer.  One side measured 7.5K to case, the
other 1.1K.  This in spite of having .25" safety gaps, 14 mH chokes, 750
Ohm/50W series R's, and 600 pF bypass caps.  I still don't know what was
different this time, just that I lost one very-hard-to-come-by
transformer.  My main RQ static gap was 10 gaps -at- .03".

I read the archives on depotting.  Since I was determined to re-use the
case and insulators, I fired up my charcoal Weber grill, put the xfmr in
an aluminum pan, and cooked it for about 4 hours.  After the whole
stinkin' mess was good and liquid, I dumped the contents of the case into
another pan and seperated the core from the goo.  After several dips in
paint thinner, I have now seperated the individual windings from the E
and I laminations.  My plan was to remove some of the magnetic shunts, but
I'm not sure what exactly these are.  I have E's and I's, and on the
two faces where the center segments of the E's meet the I's (represented
by # in the diagram below) there were a pair of small (~ .5" x 1") curved
metal springs.  

                          Where are the shunts?


            SSSS     PPPPPPP     SSSS
            SSSS     PPPPPPP     SSSS
            SSSS     PPPPPPP     SSSS
            SSSS     PPPPPPP     SSSS
        ----SSSS-----PPPPPPP-----SSSS----
       /  / SSSS     PPPPPPP     SSSS \  \
      /  /  SSSS     PPPPPPP     SSSS  \  \
     |   \  SSSS     PPPPPPP     SSSS  /   |
     |    \-SSSS#####PPPPPPP#####SSSS-/    |
     |     |SSSS|   |PPPPPPP|   |SSSS|     |
     |     |SSSS|   |PPPPPPP|   |SSSS|     |
     |     |SSSS|   |PPPPPPP|   |SSSS|     |
     |     |SSSS|   |PPPPPPP|   |SSSS|     |
     |     ------   ---------   ------     |
     |                                     |
     |                                     |
     |_____________________________________|

            --------------------------    
           /                          \    
          /       I's                  \    
          \                            /     
           \--------------------------/      
                             
        ----                          ----
       /   /                          \   \
      /   /                            \   \
     |    \                            /    |
     |     \     -----      -----     /     |
     |      |    |   |      |   |    |      |
     |      |    |   |      |   |    |      |
     |      |    |   |      |   |    |      |
     |      |    |   |      |   |    |      |
     |      ------   --------   ------      |
     |                                      |
     |            E's                       |
     |______________________________________|

After reassembly, I plan to reuse the case and insulators, fulling the
case with melted Vasoline jelly, this so it won't leak after it gels.
Anyone know a way to buy Vasoline in bulk so I don't have to carry a
shopping cart of small jars to the register?

Gary Lau
Waltham, MA USA