Quad 833 coil

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

Original poster: "Sundog by way of Terry Fritz <twftesla-at-qwest-dot-net>" <sundog-at-timeship-dot-net>

Hi All!
 
            Well, my first attempted light was a bust, nuthin' happening at
all.  I was getting some really screwy pairs of oscillations, so I broke out
the HV probe, and started by troubleshooting 1 side at a time.  It's a
push-pull coil, so I had to check everything over.  
 
    For testing I removed the secondary, dangled some coax near the primary,
and ran the coil at between 10 and 25 volts input to the MOT's.  This was
enough to give me a *solid* oscillation of the setup with very little power
actually going into it, as the tubes have to dissapate all the power.  My first
problem was a strong 1.8mhz parasitic that I traced down to the lead between
the plate and the tank circuit.  I added a pair of ferrite core chokes I
scavended from a magnetron outta a microwave and that damped 99% of it.  Next I
tried to get rid of the nasty 735khz signal.  Tracking it down was trickier,
and I still haven't found it's source.  
    But, I got the coil running and tuned 1 half at a time (to ~350khz,
secondary oscillates at 357khz.)  Now I get a nice double-beat waveform when I
look at the coil primary with both halves of the tank circuit hooked up (flat
DC hump where it charges the tank cap, and then an RF blowout, followed by
another DC hump).  The tubes are charging the tank circuit at about 49khz, and
on top of it all I get a nice smooth 60hz buzz in there from the filament
trannies.  
        Anywho!  Now that it's debugged, I'm going to try and get some spark
photos of it running.  Wish me luck!  
 
On a side note, this is a serious toy :)  A few kW available power from the
MOT's, 4 833's for over 3kw handling ability, and a super-tight coupled
secondary.  I'm expecting to smoke the filament tranny's windings (they get
scorching after 10 min of idleing, 10v40A), or the tank caps (panasonic MMC's,
a single string)  Yeeeehaaa!!
 
    
---------------------------------
Shad (Sundog)
G-1 #1203