On the fly tuning of a TC

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

Original poster: "Jason Petrou by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jasonp-at-btinternet-dot-com>

Hi all,
 
I was tuning my 360W coil yesterday and it took me about two hours - I was
finding it very hard to zero in on the exact point on the primary tap.
 
I recently worked out how to control a 12V printer stepper motor using the
RS232 port of my computer (serial). The motor had been salvaged from an old
epson laser printer, and worked in one degree increments - almost perfect for
tuning an SG.
 
Anyway I bought some serial cable (the type that is usually used for direct
cable networking) and cut off one of the ends, and connected it up to the
motor, (and plugged it in to a 12V tranny etc) and connected it to the bottom
of my TC. I fixed a perspex arm onto the shaft and one to the my fuse holder,
then used two U shaped pieces of perspex top hold them in such a way that the
holder assembly could slide up and down the arm, but not to the side, rather
like a piston and crankshaft mechanism.
 
I screwed the motor underneath my TC's primary winding, with an 18mm piece of
acrylic as an insulator, and connected the arm assembly. with the power to the
TC off i tested it and although it was a little jerky the holder could slide
from the 4th to the 12th wnding - enough movement for me. I pluged the cable
into the computer and run the basic written pulse program.
 
I turned my NST on and amid a shower of sparks from the primary started to move
the holder. suddenly a streamer hit the primary (something very rare - i use a
double toroid configuration) and the computer turned off. It turns out that I
had fried the mainboard of the PC (it was a crappy old 486 not worth the £10 I
paid for it) thorugh toe primary cable
 
I have still not learnt from my mistakes, and am trying to develop an new trpe
of on the fly tuning. Please reply wiht ideas (or just to take the piss!!!)
 
Thanks all
 
Jason