Re: Restoring old Tesla coils

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

Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Antonio

At 09:18 PM 9/21/2002 -0300, you wrote:
>Hi:
>
>I am restoring an old Tesla coil, the one that appears in:
>http://www.coe.ufrj.br/~acmq/tesla/oldtesla.html

Neat!

>
>I cleaned everything, repainted the base, polished and varnished
>the primary assembly and the top terminal, and am now working
>on the secondary coil. 
>It is wound on a thick cardboard tube, with thick magnet wire
>(~#20). The wire is intact, but has some scratches in the
>insulation. It is also a bit loose over the tube (there is no
>coating over it). I am trying to avoid to have to rewind the
>whole coil, by moving the loose part to one end and rewinding
>just the last few turns. This appears to be possible, but will
>be just a little less work than to rewind everything. 

Tightening the wire does work fine.  The form shrank a little over the
years and your plane to remove a few inches does work an I have done it
myself.  It really is not to hard one you get a good loop to work with.

>Would the scratches in the insulation be a serious problem
>if I try to operate the coil? I can add a layer of varnish
>over the coil, but don't want to use a thick layer, or to
>let the varnish reach the original tube below.

Spot painting the insulation with varnish in the damaged areas would be
fine.  I doubt there is much serious turn-to-turn voltage stress on this coil.

>This coil is quite strange. I don't see any sign of connection
>to the lower end of it. Maybe a piece of metal foil was originally
>used to make contact between the coil and the base, that has a
>connector for grounding.  

It should have "something" for a base ground.  Maybe something broke off or
is missing.

>
>I found also a very strange Tesla coil, apparently part of a
>very old radio transmitter made in Germany (by G.F.D.T.). It has
>a 1 turn primary, a quite small secondary coil, and a primary
>capacitor split in two, one at each side of the primary. Each
>capacitor is made with four test tubes mounted upside-down.
>The capacitors are interconnected by an adjustable spark gap
>with two balls. See the picture:
>http://www.coe.ufrj.br/~acmq/tesla/gfdt1.jpg
>Along with it there is a coherer receiver (look at the right side).
>It is identical to this:
>http://www.chss.montclair.edu/~pererat/r_0100.gif
>Any information about these devices would be appreciated.

Neat stuff!  But I know nothing about them.

Cheers,

	Terry

>
>Antonio Carlos M. de Queiroz
>