This is turning out to be a small amplifier. Someone on QTH.com has a 6 meter amp with a 4CX10,000 tube for sale. Love the articles Jim. Mike
Hi Mike. Yes, I know that particular 6M amp well. (I have all the complete schematics for it. It was built by ASI). A few years ago, a few of us spent umpteen hrs, and a few months trying to figure out why it wouldn't resonate below 70 mhz. I assumed way too much. Short story was the original new Eimac 4x10 tube was swapped to a newly rebuilt Econco Eimac 4x10.... right at the factory. ASI needed a new 4x10 for a FM broadcast PA, and removed the new Eimac 4x10 from the 6M amp. Later on it was replaced by the Econco tube. Shipped to end user...without re-testing. The internal stray capacitances between various elements inside the Econco tube were a tiny bit different than the oem Eimac tube. The 2 x series 17 pf HT-57 caps hanging off to one side, of the... one off plate circuit resulted in 8.5 pf..when in series..which was too low a value for the Econco tube. One cap removed, and total C increased to 17 pf. Bingo, then resonated on 6M, problem solved.
It's a cathode driven affair, complete with PI tuned input, and grids RF grnded with a mess of bypass caps..and bias applied to the grid. Screen is bonded directly to the chassis. B+ and screen supply, and bias supply are all wired in series.... sorta like a Collins 30S1..on steroids. It's 800 lbs, comes in 2 x cabinets. Power supplies are at the bottom of cab #2. 6M RF deck is in cab #1. The mating 144 mhz RF deck was never built.... and was supposed to go in the top of cab #2..above the power supplies. It truly is a thing to behold.
Is this the one you asked if I would be willing to go look at? In my old QTH?
If so, he just got that damn thing!
--Shane
WP2ASS / ex KDt6VXI
