Jim, I can't see how a tuner would provide transient protection except by arcing between plates which is still highly undesireable. I need something that would shunt a high transient to ground but not have high insertion losses.
Bill, the ARB704 protects the control lines like amp keying and ALC but not the RF on the coax between the transceiver and the amp. This is the route that killed the finals in my FT2000.
Thanks for your responses. 73, Jim
Question to Jim: you mean to use 2 antenna tunners?
Greetings from Venezuela
Assuming yes to above, I pulled out a copy of Radio Handbook (23rd ed) by Bill Orr. The HF amps all have a high voltage "transmitting" cap before the PI tuning. This is 0.001pf at 15Kv-DC. On the output side of the tank circuit, at the S0-239 a 1.0 millihenry RF choke (0.30 amp) is placed. Between the DC blocking caps and the DC shunt to ground.
If tube arcs over, the cap should block the DC and the Choke will also.
Checking my Ten Tec Titan 425 schematic, it has the same configuration. It never hurt my SS rigs.
Best of Luck...
* Transmitting Cap means one intended for high power RF and can handle the high RF currents it will experience, aka. expensive thoguh cheap insurance.
To the OP My guess is the arc was not the "cause" and may have been caused by the Yaesu. Arcing readily happens by over-driving an under loaded amp as in the case of overshoot into an under loaded amp. Many Yaesu's are known to overshoot. So the best protection is to make sure your amp is properly tuned toward overloaded. You can tell this by watching the grid current in a GG triode amp (screen current in a tetrode). If it soars you need to unmesh the loading cap till the grid current reduces. Flex 6xxx's as far as I know do not overshoot