Hmmm how about the chances of parts blowing up? That's what I hate the most about SSTCs.
Well the tube will stand hell in most cases for short durations , the capacitors will stand a lot if they are the Russian RF ones and the MOT is dam hard to kill
. I use light bulbs for the grid leak resistors and may have lost one or two but they work well and stand a fair bit
Out of the few VTTCs ive made, I have not lost a single tube , cap or mot ( my 811a has been though a lot xD ) . The most ive lost was a few primary due to arcing to the secondary as I was pushing the coil rather hard for its size and maybe a lighbulb or so .
The MOT caps in the level shifter are robust , Just have to watch out for the level shifter diodes as I lost a few of them from ground strikes .
The VTTC is a less complicated circuit wise than a SSTC but harder to tune , Not saying thay are easy to make but it uses less components and has less failure points over a SSTC and is simpler
SAM_1012 by
TwirlyWhirly555, on Flickr
That picture is a whole VTTC setup , at the back is the mot with RF bybass capacitors , level shifting diodes / MOT capacitors , Top right behind the primary is the main tank capacitor .
bottom left is the 811a vacuum tube and to its right is the feedback capacitor and resistor ( light bulb ) , then thers the secondary / primary / feedback windings . There is a LR sunbber on the connection from the primary to tube anode to help protect the tube encase of a tube arc over and there are RF by-pass capacitors across the 811a heater connections / cathode .
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