Not true, a flashover in a valve is just as destructive as a similar condition in a transistor and cannot be snubbed without removing the supplies. We have big crowbar switches here. Lee. ________________________________________________________________________ This e-mail has been scanned for all viruses by Star Internet. The service is powered by MessageLabs. For more information on a proactive anti-virus service working around the clock, around the globe, visit: http://www.star.net.uk ________________________________________________________________________