Re: 813 VTTC Problems

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Ed Phillips <evp@xxxxxxxxxxx>

"   Still trying to get this dual 813 VTTC going, with no luck. The
main problem right now is figuring out what to do with the extra
grids (G2 and G3) of the 813 tubes. I didn't have anything to go by,
so I connected both G2's together and connected them to the 4KVDC
supply via a large 10kohm resistor, and left the G3's unused. The
resistor violently exploded the instant power was applied. It's my
understanding that the G2 of a tube isn't supposed to draw any
current - so something must be wrong somewhere! I'm suspecting that
one or both of the tubes may be bad; I'll be doing more tests but
this time with a Variac, to confirm if this is the case or not.
   How exactly should the G2 and G3 grids of these tubes be connected
to the circuit? And are they actually supposed to draw current?
   Thanks for any advice."

	If you're using them in the pentode configuration you should tie g2 to
the filament (preferably to the center tap of the transformer but not
essential).  I haven't bothered to look at the data book but the screen
grid (g2) can draw plenty of current.  You didn't mention the grid (g1)
bias when you did this experiment.  Tubes are probably undamaged.

Ed