On Wednesday 11 November 2015 07:59:32 Peter Blodow wrote: > Gene, > telling from my rusty experience from waybackwhen (and the RCA > transmitting tube manual of 1962) I suspect that the one glowing tube > has too much positive DC grid voltage, maybe resulting from a faulty > driver (suspect: capacitors). The ouput power you are measuring comes > from the other 833 alone which is possible if the circuit is designed > for class C operation. > > A 833A can carry 1650 W without forced air cooling at 4 kV on the > anode so this heating power is probably not all high frequency, but DC > anode current, I guess. At less than1 kW it's not yet supposed to > glow. The manual says: "At a plate votlage of 4000 V, a fixed bias of > at least -90 V should be applied". If the fault occurred suddenly, it > won't be a HF balance problem, these more likely tend to sneak in. > An 833C (they use 4, at about 2800 volts, 2 in parallel for rf, 2 in a complex, almost dc coupled feedback as push-pull to modulate) will show some dim color in the rf pair, and a couple hundred F warmer for the modulators, when its singing on key. RF plate current for the pair is a hair under half an amp, and the modulators combined idle at 80 ma each, peak at about half an amp at 100% on the trap pattern.
The C version, (these are all Chinese tubes now) means molded carbon/graphite plates, capable of 2 kw dissipation if the glass is cooled, but these aren't, but they'll light the room up pretty good doing it. If they don't run any hotter than I left them running, they should last at least a year. > (I have built an audio band amp with two 807s P-P once upon a time in > the early ages of rock'n roll music and dealt a lot with those > transmitting tubes.) Small fry. I once had to rescue a 2500 watt tube amp. Had about 3 feet of 6550's in it. Should'a been 3 feet of KT88's in a Williamson circuit, would have sounded a lot less like an overdriven PA system. For the night club, it was overkill by at least 25db. I had shooting muffs on, good for -30 db, and the drums still hurt my ears. I did not solicite any more of that sort of work, my ears have been abused enough... I have "carhart" notches 120 db deep at 4 kilohertz in both ears, way too much lead thrown downrange without any muffs back in the '60-70's. My P.O. Ackley-06 is on its 4th barrel now. Slow learner? Probably. :( > Peter > > Am 11.11.2015 11:15, schrieb Gene Heskett: > > Then I have to go see if I can restore a 60 yo 1kw Gates BC1 AM > > transmitter, again. Something in the feedback loop around the > > modulator is causing a severe unbalance in how hard each of the pair > > of 833's is working, so one is running bright red and the other is > > nearly invisible. No way in tuncket it could ever pass a Proof of > > Performance. That, and his < 3/8 wavelength stick is so far out of > > tune. I have no clue where the J is, but the effective R is at least > > 70 ohms, send out a 1000 watts & the Bird meter says nearly 200 is > > coming back. That stick has 2 sets of ICR antennas on it now that > > weren't there the last time the doghouse was tuned up. He doesn't > > quite grasp that that stuff changes the towers tune. I've been > > looking for a GR Bridge, but so few of those were made that anything > > that might work is north of $1k USD. None are less than 50 yo. > > Cheers, Gene Heskett > > --- > Diese E-Mail wurde von Avast Antivirus-Software auf Viren geprüft. > https://www.avast.com/antivirus > > > ---------------------------------------------------------------------- >-------- _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
