IAIPS-ACIPS@USC-ISI.ARPA (12/31/85)
I concur in your assessment of EIMAC's 4-400 tubes. I built a Johnson Viking Thunderbolt Linear Amplifier back in 1960 (a pair of 4-400's) which gave me outstanding "glowing plate" service on AM linear, RTTY and I even screen grid-modulated them for a time! Since 1960, the amplifier (with finals still in their sockets) has been moved (by commercial/Navy movers) from Massachusetts to California; then from California by ship to Hawaii; from Hawaii back to Massachusetts, and then to Virginia. You can imagine the vibrational shock to the filaments alone. Yet, after 26 years of operation, and all that physical abuse, the orig 4-400s are still doing their job. For that matter, so are the five voltage regulator tubes and the two LV rectifiers. The only thing I've touched after all these years was to, early on, replace the 866As with solid state equivilents. I will keep this linear until the day I die. Continuous coverage from 3.5 through 28 (no bandswitches) and Class C operation on CW (70+% efficient vs 30+% Class AB). I doubt if I'll have to change the finals before that day either!! I thought they'd at least get gassy and start degrading. However, I also have the original 6146Bs in the SB-401 (circa 1966). Not that I'm cheap or anything, but these things never give up, and I have woefully abused them over the years with lots of stupid mistakes. I doubt if the new tubes today undergo the QA and manufacturing care that my old ones did. Living proof, I guess. 73, George W1TQS/4
Karz.Wbst@Xerox.ARPA (01/04/86)
George, Too bad you replaced the 866A rectifiers. I had a homebrew 813 rig in the old days (also screen grid modulated!) using 866A's in the power supply, and must admit that I miss the deep blue glow they imparted to the shack. The only thing you'll ever get from the solid state replacements is a sound and light show when they burn out (hi). 73 Bob Karz K2OID