Vacuum tubes.... As many times as they try to replace them, they still are around. Kudos for those keeping the technology rolling. There's just something about tube audio that keeps me listening.
When I first saw this I knew exactly what it was! I worked at a 1000-watt AM station in Florida in the early 80's and faced this lovely unit every day. We did our shutdown every night and recorded our plate voltages and output and a couple other things. In the couple years I worked there, it never wavered at all. I figured I'd never see one again. It was a great amp! Thanks...
Interesting video! I remember this transmitter back in the day! If I remember correctly, the power supply used 866A's for the rectifiers. These units are of a solid build!
+Frank Ferraro Yes, it did use 866 rectifiers but with the power transformer I use it needed to be a bridge so I put in four 866 solid state rectifiers. It is built solid. Choke input filter to a Pi filter with a resonate capacitor cross the first choke. They did not spare the iron in these things. Nowadays you could probably make a small car out of the steel in the cabinet... Good to hear from you, Frank.
Thanks, Bob. In all honesty, I think the pair of 4-400A's is the most striking amplifier I have built into this old 1947 Collins cabinet. I have also had a single 4-400A, 3-1000Z and 4CX1000A. The 4CX is definitely the most powerful tube with a full 1500+ watts output but it just doesn't have the charm of the glass tubes. 73
I have had a lot of fun with this cabinet. All the power supplies are built below the RF deck and the plate tank circuit, with a large roller inductor above the RF deck and have run a 4CXC1000A, a pair of 4-400A and a pair of 3-400Z built on different chassis that I can slide in behind the glass window. I kept ;the 4CX1000A in the cabinet for over 30 years but then started reinstalling the glass tube amplifiers for their beauty but, at this time, have the 4CX1000A chassis back in and run it mostly on 40M. I paid $75 for the cabinet and whatever components were in it in 1975 and picked it up from a small town near Atlanta, Georgia. Thanks for your comments. 73 WA4QGA
Absolutely beautiful Brother! I've always wanted a Collins 20V but even if I had one I'd have no room.. I do have a 4-1000A GG Amp with a picture window that when ran at full power really glows and puts out amazing power, I have a pair of 4-400a's in GG which I run at 4KVdc and it will achieve 1600 watts to the antenna, I have two other 4-1000a amps that I rarely use but in reality I use my Drake L4B more than any because its simple, compact and at the other end the difference is not noticeable. Besides the 4-1000a is a little harder on my antenna than the L4B having vaporized a plastic insulator on my 80 Meter loop and set a plastic insulator on fire at the end of my multiband dipole.. I actually have a video of an awesome corona ball that occured one my 80 meter dipole when running in AM mode with the 4-1000a.. Its all fun stuff!
I have chimneys and have used them on other amplifier builds but it is necessary to have an enclosed and pressurized chassis to blow the air up and past the tube filament and anode seals if we are going to use chimneys. For 24x7 commercial usage, it is surely a good idea but I do keep a decent air flow over the tubes and for amateur service it seems OK. Some of the amplifiers commercial amateur radio amplifiers just blow air across the glass of the tubes and that seems sufficient. Chimney's are classy and I like them but I did not build it with an enclosed and pressured under-chassis so I figure without that being done properly, it would likely just end up restricting air flow from the top of the chassis. I think the big glass triodes and tetrodes are beautiful with their plates running orange hot.
You definitely have great knowledge and style on all of the tube equipment you have. What type of dummy load do you use testing your RF amplifiers? Resistance value and wattage ? Cool tubes! All your videos are great and informative!
Thank you for your nice comments. I am pleased you enjoy the videos. The dummy load I use most often is a 600 watt 50 ohm Bird dummy load. I can put much more power into it than 600 watts for a short time and it is OK. I have quite a few dummy loads from very small GHz level 50 ohm SMA loads to the 600 watt size with N connectors. I have loved the look and style of these amplifiers from the very beginning of my interest in electronics and always wanted to have one of the larger amplifiers. Building them is really the only option and being lucky enough to come across some of the vintage cabinets and components. I enjoy sharing these instruments on RU-vid as most amateur operators today prefer a single unit (tranceiver) and maybe an amplifier, all with as much auto-tune as possible. I see the reason for the automation as it frees up operator to talk more and tune less and the possibility of damage to equipment is probably lessened by auto-tune circuits but I still love the look and even the smell of this old equipment.
Yes indeed, a beautiful amp and no doubt a great performer. How much drive power is needed for 1.2kw out, and are all the grids connected directly to ground?
The output of my Collins 32S-1 is 80 watts and it does not take all of that to drive the grid current to 200 mA which gives maximum output of about 1350 watts, so, I don't know the exact amount of drive necessary but definitely something below 80 watts. Probably about what the Eimac data sheet predicts. The grids are not directly connected to ground for DC. They are connected to RF ground thru capacitors mounted right at the tube socket to chassis at each of the three grid connections. At one grid connection, there is shielded cable (RG-58) going to the grid meter which has one terminal grounded to monitor DC grid current. It is an amazing performer and while not this very 3-1000A amplifier chassis but I have run this amplifier since 1983 with a 4CX1000A with virtually no issues. I hear fellows on the air that comment that their (model number) amplifier has been working for 10 or 15 years and they retire it for a new one. If your amplifier is built with the massive surplus components you can get today, it can last a life time. Thanks for your comments. 73
+Bishka100 I guess my next project is refrigerated air for it. :-) It is nice in the winter but it does heat up the room quite a bit. All in all, the entire unit is probably about 50% (or less) efficient so I am radiating 1200 watts or more of heat into the basement where I sit.
+ElPaso TubeAmps Ha,ha. when I was a kid, living at home, we lived on a boat and my cabin being so small, my valve amp would take the chill out of the air too. Our two cats brought a rat home once and it escaped into the bilges. The next morning I woke-up to a little furry face watching me from behind my amp's ventilation grill. It didn't do any harm though.
+Bishka100 That's a nice story about the mouse. It is getting the time of the year that when I work in my shop I am visited by a lot of strange looking desert bugs. I don't harm them but some of them do give me the creeps and I have to take them outside. Sometimes I talk to them and I think they understand. Maybe I have just been around high voltage for too many years.
A pair of 4-400A at 3600 V on the plates will deliver a steady 1200 watts to the antenna as measured on an accurate Bird wattmeter. They are actually (should be) the same because if you load an amplifier to 1200 watts average, you should not "talk" it past that point in PEP power but often times we do. Distortion increases rapidly past that point. Cleaner and crisp audio is often times more penetrating than louder audio. I keep my drive down so that I do not exceed the average power level I load an amplifier to. The amount of processing and compression I often hear on the air makes it hard for me to copy some SSB stations. "Talking" the plate current to reach the maximum loaded power makes a signal sound loud (distortion makes any signal louder) but it becomes muffled and hollow sounding to my ear and hard to copy.
Sadly, that is true. I wish it was as original as the day it left the factory but 40-50 years ago when AM was not popular anymore, these beauties got trashed. I think the fellow that I got it from tried to turn it into a CB "linear"... but I think it is still beautiful... :-)
