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i have a ameritron al80a amp want to know if i have bad tube and if the 4-400 tube will wrk inplace of the 3-500 to le me know if the tbe is bad. i turned it on blew fuse replaced fuse amp worked full out put. turned on again nooutput blew fuse. can anyone give m a hint. i was told the tube could be shorted was told that 4-400 will work. if it works then i will buy a new tube 3-500. the 4-400 is a good tube i can get it from a freind for 20 dollars. anyone help. pleas email me prinker@rochester.rr.com or call me 585 765 2642. thx god bless

Yes, a 4-400 tube will work. The impedance will be off so the SWR to the rig will be high. You will probably get around 500 watts out or a tad more. I have run this test already as I have numerous 4-400's laying around. Mine are the carbon plate tubes so it takes more to drive them. But it work fine for a test.

Barry, KU3X