813 tube coil, 4-125A vttc, sync gap TC
I finally tested an 813 tube in a tube coil. I had this nice 813 with the
red RCA emblem on the glass, for about 5 years, but I had never tried
it out. The tube looked clean; no burning or black deposits inside the
I tied grid #3 to ground, and tied the screen and control grids together,
and popped the tube into my small tube TC, and fired it up. The coil
roared to life and gave a nice 16" spark. I didn't bother to optimize
the grid drive, grid resistance, etc., I just left it the way it was from
the prior set up using the 833A tube which gives 19" sparks.
Next, I separated the control and screen grids, and tied the screen
grid to the HV supply through a 40k resistor, this also worked well,
and gave the same length as before.
No redness appeared in the robust graphite plate, although I didn't
really run the unit for very long.
I also tested two 4-125A tubes in the same coil (one tube at a
time), with the screen and control grids tied together. I obtained
a 5" spark with either tube, the sheet metal plates ran orange/red
which is normal for these tubes.
I've posted the specs for this coil many times in the past, and this
coil has been shown on my videotapes, and this new work will
appear on my new tape that I'm making. It will take quite awhile
before this latest tape is done. Let me know (off list) if you'd like
a text file of my tape index for all 22 prior tapes. These tapes are
$16 with quantity discounts available.
I also ran my sync gap TC today, and tried the 4" by13" spun
aluminum toroid, at 1000 watts, the coil gave 44"+ sparks with
multiple reaching streamers, which looked impressive. These
spun toroids are available for $119 including shipping. Send
check or money order to John Freau, 49 Thiem Ave, Rochelle Pk,
NJ, 07662. This toroid can be seen at my website at:
< http://members.aol-dot-com/FutureT/index.html >