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Author Topic: What AM tower is this (Paul G. Thompson or anyone?) Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 10-09-2003 12:19 AM                        I have noticed that some brands of tubes glow easier than others. Of the bunch, the only real problem transmitter has been the 20KW continental. That CCE transmitter we are using in Q98 is very good to finals. The bottle thats in there is pushing 3 years, and she still is making power HT 5's may be incorrect, I'm not sure before my time. The BTE-20 had a cavity and coax fire a few years back, but after the rebuild has been running flawlessly, no driver problems either, I'm happy to report.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 10-09-2003 12:50 AM                     Luciano, what's the cathode current running on your 6L6's? Are you using self bias or fixed bias? If you are drawing up to about 66 mils with a zero-signal condition, I would bet they are glowing. For a zero signal condition, 54 mils for a plate voltage of about 350 volts or so would be about right. I'll bet you are using self-bias. Sounds like the plate currents you are running are sufficient to draw the butthole through a skunk. I'll rathole some of the 4-400's for you. Pay the postage - they are yours.  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 10-09-2003 03:51 PM                     Paul, the 6L6's are running on self bias ,having a wirewound resistor of 510 Ohm connected to the cathode of both tubes ( 1 resistor for the 2 tubes + the bypass cap)I'm thinking about putting one resistor for each tube and see what happens.I didn't take current readings on them yet, will do it this weekend. with zero signal they're running hot but hardly show any glowing spot.with any signal they start to go blood red. Thanks for the 4-400, I'll email you soon to arrange the shipping  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 10-09-2003 05:33 PM                     Hmmm....510 ohm resistor common to both cathodes is about 63 mils total. Or, roughly 31.5 mils per tube. That does not sound too unreasonable. However, not taking screen current into consideration, the plate dissapation is about 11.5 watts per tube. I'll have to insult the tube manual and see what the maximum allowable is. When I get home, I'll plot a loadline and see where it falls in the EcIb curve. Been 40 years since I done that, but I'll try... By the way....what is the screen voltage?  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 10-09-2003 10:34 PM                     Being a pushpull UL stage, the screen voltage is the same of the plates. according to the specs. taken from the RCA manual, when the screen of each tube is connected to a tap on the output transformer, is permissible for the voltage to be as high as 500 volts. on the amp, the screens are conected to taps on the output transformer and have a 220 Ohm resistor in series with them . also according to the manual, the no signal current for them in self bias,Class ab1 is 44mA , with signal 100mA .the recomended cathode resistor on the manual is 248 Ohm . going back to transmitter tubes , what's the use in a transmitter for a 828 and a 4E27A / 5-125B ? I have one of each but have no idea about it's use ( here they're being used as decoration )  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 10-09-2003 10:36 PM                     My favorite audio tube is the 6C33 triode which is used as a voltage regulator tube in Russian MIG fighters. It works really well for building OTL type tube amps as well as output transformer type. It has a very low plate impedance to begin with. Running 6 each of these on two mono block amps will cause the generators at Hoover Dam to stall! There is another incredible audio tube that is also Russian and thats the 6H30....similar in looks to the 6C33 but capable of higher power dissipation and was used in Russian nuclear bombs. Both these tubes are now easily available on the normal vacuum tube market and commercially produced amps are also available for big bucks. Mark  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 10-09-2003 10:45 PM                     Well, with the parameters you are using and the tube still glows, maybe the next set of bottles should be the JAN 5881. (Military version of the 6L6GC.) Definately industrial strength...  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 10-10-2003 12:15 AM                     JAN tubes! (I have about 6 JAN-Type 5R4WGA and have no use for them except display and they're NOS. and the JAN equivalent for the 12AU7) Well.. before I start hunting for them, I'll redo the circuit all again, even if I did that before, but wwhat's one more try? these amps were a restoration project, a friend gave them to me and I rebuilt the entire thing ( new tubes, sockets capacitors and some resistors, before everything was de-assembled I drew the schematic for it and made sure it was right. the transformers and filter choque seemed ok, I replaced the connection wires on them ( they have solder points inside the casing for the wires) stripped everything off the base, repainted and reassembled the circuit. the original tubes on them where the ST16 shaped 6L6G for output, 6N7 for phase split 6SF5 for pre/input and 5Z3G for rectifier. Josh is right when he said that some tubes glows easier than others,when I saw the glowing tubes, I shut everything down, a while after I put a set of old 6L6 I have for testing purposes and powered up again, they took a little more time to go red than the new ones. they doesn't have the brand on them anymore and doesn't looks like a Russian tube but doesn't look like a decent 6L6 too and did get reddish plates. Now 2 pictures of the afterlife of a TB4-1250 tube : (sorry about the quality of these pics.. took them with a webcam)  |  IP: Logged Jack Ondracek Film God Posts: 2348 From: Port Orchard, WA, USA Registered: Oct 2002 posted 10-10-2003 12:39 AM                        Paul... speaking of industrial quality. I have some old JAN 807s at the Port Townsend drive-in... found them somewhere around 35 years ago. They're still on the shelf. There aren't enough of them to match up a full set, but have been used as spares from time to time over the years and are still perfectly fine.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 10-10-2003 12:41 AM                     Jack, the 807 is what I am using to drive the 4-400A's in the RF line with the Collins. Very seldom do they turn sour. I use JAN's if I can find them. For every 3 sets of 4-400's I lose, I lose only one 807 because of low transconductance. Luciano, the JAN 5R4 was crap. The 5881's, 6146's and a bunch of others could stand up to the jar imposed on them when a 38,000 pound aircraft experiencing an arrested landing (basically, a controlled crash) on navy-issue aircraft carriers. Cat shots, too! The Radar power supplies used the 5881's and 6146's as regulators in the days of vacuum tubes. They hardly ever failed. Yes, Josh is right. Some do and some do not glow. I am aware of this, and after I discovered you were running Class AB1 Push-Pull with the low plate current you were using, I made the posts for you to read. Had the idle current been in tha area of 65 mils or better, I am sure they would definately glow. I think the glow Josh has on his 6L6s' is because of roughly 500 volts on the plates and a little lower bias he has on those things (I forgot what it was) is causing excessively high idle plate current. Under continual usage, I don't think he will get very good mileage out of them. I never did find out what the plate current was in the applications he was using them for.  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 10-10-2003 01:55 AM                  Luciano: GREAT pic of your lamps! Luv 'em! I am inspired to do the same thing! (But would light the Filaments for a "night-light") Also, I wouldn't give anyone a plugged nickel for 5881's...they are a POS...much rather use 6L6GC which are rated the same or in some cases better and will out-perform the 5881's for "grounded" people. The 5881's "small" bottle was sooo prone to overheat that it wasn't even worth using. 6L6GC were/are a MUCH better choice. Also, the 5V4 (in ALL versions)is a great rectifier for the applications they are intended for. Much rather have a 5U4 though... Most of the vacuum tube regulators I came across in the military used 6550s. As with all electronic devices, they will perform VERY well if used within their specs. AND!!! even better if conservatively used. I have junked more 5881's than I can say and happy I did so! A true POS! >>> Phil  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 10-10-2003 02:43 AM                     Luciano, those are nice looking lamps. One of those tubes (the bigger one) looks like a 4-1000. The only information I have on the TB4-1250 like you have is a power triode that is about 7.8 inches high. Here is a 4-1000. This would make a nice lamp. The filament wants 21 amps at 7.5 volts. It is 9.63 inches high and 5.25 inches in diameter. It weighs about 1.5 lbs. The one in the picture was given to Josh. Here is a cute little devil: Phil, If you junk the 5881's, send them this way. The 5881 was rated at 11.3 watts with a 4200 ohm load where the 6L6GC was 10.8. There is only one milliamp difference in zero signal plate current, probably since the tube is physically smaller and the Rp was significantly higher in the 5881. The 5881 is not a direct replacement to the 6L6GC, but it will work. It is, as the RCA Tube Manual says, "similar" By the way, what were was the color of the octal base of the 5881's you had so much trouble with? The ones I had good luck with were built to the orginal military specification. Most had the brown octal base. I will be happy to take them off your hands. I'll even pay the shipping. I have had very good luck with them in the '50's and 60's. Maybe the newer ones were garbage, but the old ones I thought were great! As far as the 6550 is concerned, that is possible. However, I am more familiar with the 6080. The old "G-51" used them as regulators in the +300, +150 and -250 power supplies. [ 10-10-2003, 02:31 PM: Message edited by: Paul G. Thompson ]  |  IP: Logged Luciano Brigite Master Film Handler Posts: 277 From: Sao Paulo, SP, Brazil Registered: Jan 2002 posted 10-10-2003 05:03 PM                     Thanks for the comments on the lamp Phil, making one isn't hard,all I needed to put things toguether on that one was some epoxy adhesive and hot glue (quite a bit of them) It's base is a plastic core taken from a 1" videotape reel. I'd not use the tube itself as a night lamp because it'd spend a lot more power than the bulb I use on top of it , also the filament in that tube is broken in many tinny pieces. Paul, the big tube is the TB4-1250 the small one is a 4E27A. The 4-1000 surely will give a nice lamp, it's a little bigger than the TB . Nice looking plate on that tube too. The other tube is interesting, I wonder why you called it cute little devil,judging by the specs in the base, I guess it's a kind of trigger tube or something close to that (a thyratron (sp?)maybe?) tech data for the TB4-1250  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 10-10-2003 05:22 PM                     -------------------------------------------- With all the paperwork, engineering studies, and attorneys fees involved just in applying for a construction permit to replace the aliing xmitter -------------------------------------------- With deregulation, there is no paperwork involved with replacing a transmitter with another of the same power rating. You don't even have to notify the FCC. Before I got out of radio (about 4 years ago), I found that transmitter sites were becoming poorly maintained at many stations thanks to deregulation. Without the requirement for a FCC licensed tech, any Joe Blow could work on a transmiiter (and a lot of sites I saw looked like it). Inspections of transmitter sites by the FCC are pretty much a thing of the past so many older transmitter fell into disrepair. One FM Collins I saw had every interlock, including the air-flow interlock, disabled. I commented that some day it would burn up, and it did. No doubt the station got insurance to buy them a new transmitter.  |  IP: Logged Phil Hill I love my cootie bug Posts: 7595 From: Hollywood, CA USA Registered: Mar 2000 posted 10-10-2003 08:04 PM                  Paul, chill out...it's just a tube. As far as sending you those tubes... sorry. I just this last week gave my last 20 5881 red-bases to the LAPD for target practice. Great tax write-off considering what the dumb-asses are paying for tubes on eBay. Ed Said: quote: Without the requirement for a FCC licensed tech, any Joe Blow could work on a transmiiter You are 100% right! Now, any self-appoined "expert" can f*ck-up anything they wish. It was really a shame that the FCC stopped the testing and the various classes of radio-telephone licenses as a qualification to work on transmitters. At least that had ensured one had read the "License Manual". >>> Phil  |  IP: Logged

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