Man it’s a miracle you didn’t get lit up! Never ever trust a bleeder resistor to discharge the caps! Please all those you do this make sure to bleed off the HV caps before getting into the HV section of any piece of equipment. It can be fatal!
I am getting a used AL-811 today and was looking for videos on how to operate, troubleshoot, and replace/repair. It is used so I do not expect it to operate as if new. Watching your video made me realize how easy it was to swap out the tubes. Question- do the tubes have to be "burned" in prior to use or are they now plug and play? Thanks for the video. Happy New year!
You should never increase drive beyond the level you initially tuned the amp at without retuning the plate and load capacitors. Small wonder why your 811's were flat.
60 watts input is the most I ever put into mine. Don't forget to fine tune each band coil on the rear of the amp for whatever your favorite frequency is. I use a Bird and Daiwa large face meter to see exact results.
That must be a newer amp than mine. Yours does look like they put the W8JI mod in it to prevent occilations. Looks like the resistor and capacitor on the floor of the amp next to the last tube. Mine an 1985 vintage 811 amp has the American made RCA's tubes with fins. I get 400 watts with 36 watts drive at around 300 plate and 140 grid. You are limited by the power capability of the transformer. You could burn up the transformef if you push it too hard! I would love to have 572b tubes in mine. But a new set of tubes wuold be more than i payed for the amp used. I have thought about putting some Chia 572b's in it but even then quite expensive. I love my 811 amp. I also agree on the power meter i have a MFJ Versa Tuner V and i think the meter is generous.
Sounds like the original 811A's were somewhat tired. I used to have the 811H and found that putting in Chinese 572b's actually reduced the output power from around 925W down to just over the 800W into a dummy load! My amp was running on 240VAC here in the UK. High power RTTY and SSTV (i.e. high duty cycles) will shorten the life of the 811A's. That's why I part exchanged my 811H for an Alpin 100 mk3 with a ceramic tetrode in it. ;)
So it's now Oct 2022. How's it working for you now ? I'm interested to know if it has held up for you over these last several years. How did you bleed off your voltage before doing that work? You didnt show that part .
I had the 811H for about 10 years and I tried one set of 572B tubes and it was a Waste of Money. They ran cooler than the 811 tubes but they produced No output power difference and they cost over twice as much as the 811 tubes. It was a very Poor investment.It’s not the tubes that will increase the output power unless you modify other components.The power supply is only good for so much so the best thing you can do is Upgrade to a larger output amplifier.I went to an ICOM PW-1 and sold the 811H though it had been a very dependable amplifier.I don’t regret the change because I love the extra output power on HF & 6 meters. Ameritron sells the 811H with 572B tubes and it’s rated for 800 watts just like the 811 version.
the 572B tubes can withstand higher power dissipation (>120W, almost twice that of the 811A tubes), and this makes them more durable with higher duty cycle modes. This is the ONLY reason you want to upgrade to these on an 811H amp: higher reliability.
An important comment here. First of all, thanks for posting the video. This is a very popular idea for many amateurs to do to their 811 series amplifiers. However: When switching out from 811A tubes to the 572B’s, it’s VERY IMPORTANT to let the amp run with no antenna or rig hook up with a set of “new” 572B’s for 48 hours or more to allow them to “burn in.” It’s also good to allow the amp to “neutralize.” This means, with again no rig or antenna hooked up, you place it into the operating mode and slowly turn both pots watching the readings for any oscillations. If the meters don’t move, you’re good. If they do, there’s information out there on the Internet on how to solve this problem. In most cases, the needles won’t move, however it’s good practice and proper technique to make this tube switch out successful.
Tom great video. I have a question i have a al 811,, question the black resister on the bottom by the tube on the side is one leg cut and also how many turns was the parasitic coils 5 or 6 on the PCB?
You need way more plate voltage at the same current to get those 572b tubes to honk. I'd recommend you not drive them with more than 50 or 60 watts, but others will surely disagree with everything I stated. ;)
@@micromashor ameritron thinks it's okay to wrong 200w from an 811, but I disagree. 150w is kinda pushing it. I have a homemade amp with 4 811s in it. It will do 400W, but that's it. The power supply transformer just isn't up to the task of supplying that much current. It's fine by me because my tubes will last forever, and they don't need a fan or chimneys. I've yet to find a datasheet for any 811 saying it's okay to get 200W per tube.
Awful background noise until the end. Something is wrong here the 572B tubes should do 600 watts pep (peak envelope power) with 40 watts drive. With his case his ameritron amp was designed to operate 811A tubes so the amps transformers are not large enough to run more than 1 or 2 at the most 572B tubes. But as long as he backs his drive down the new tubes should last a long time as they idle along. One last thing do not handle ANY Vacuum tube with bare hands use clean rubber gloves to preserve the life of the tube.
You know been seeing a lot of these tube swaps with the 572bs the 811H with the 811s WILL do 600 carrier with about 700 to even 800 watts on the peaks but that's driving it hard. I know I have repaired a few of them for people and even owned one for the hell of it they all are about the same and this was on a Bird 43 watt meter. Now you can get more out of them with the 811s simply get rid of the power doubling plate supply build a external Full Wave Bridge supply at about 1900 volts don't go beyond that or things will start coming apart quick LOL. With this mod you will see 900 watts out on the peaks BUT those 811s will not last long at that point or put in the 572bs raise the plate voltage to 2800 to 3000 volts change the blocking cap at the plate choke and the plate choke if you like it ran 1500 all day pep ran one for a year no problems at all. One thing to keep in mind the variable plate and load capacitors will be at max levels even beyond that just keep them clean NO DUST and when you tune the amp BE SURE that your swr is flat or at least 1.5.1 or better BEFORE you start tuning it up also be sure the relay in the amp is clean. One more thing ALWAYS make sure the caps are discharged after they bleed down short them to ground with a screwdriver then get a wire with alligator clips on the ends and clip the caps to ground caps have a way of coming back to life when you least expect it.
@@beekeeper8474 Well what it really comes down to is bang for the buck. Without having to design a all new amp the best way really to squeeze out about 900 to 1100 out of a AL811-H (SSB ONLY) is to change the taps around for the transformer. So the first thing you should so is set it up to run on 240 Volts not 120 volts will draw a less current and run better. I think the blocking caps in those are 5kv so you should be ok there. Now those 572bs will need more plate voltage to really get them to work the cheap way to do this is to hot tap the transformer in the amp so if you have 240 going into it set the taps on the back to something like 220 or 230 this way the transformer will make more plate voltage REMEMBER this will heat it up more and is harder on the rest of the parts in the amp! I cant remember what the filter caps are rated at but I am sure they would be close to the limit. If they are rated at lets say 450 volts buy new ones and put in 500 volt caps. Now you HAVE TO get a filament transformer and not use the filament taps coming from the transformer because when you re tap it for higher plate voltage it will also raise the filament voltage as well so you need to keep the filament voltage around 6.3 volts it is a little bit of work to do all this. And also you will have to check the biasing and make sure everything there is in check. After all this is done the reality is that no one will see the difference really in signal strength at the other end. All what I have mentioned is really the basics to keep it from coming apart but if it were me I would not do all of this to that amp it is just beating it up. If you want a honest 1000 to 1300 or better out of 4-572b's find a old Dentron Clipperton L amp and freshen it up. I'm not saying what you want done cant be done but like I said bang for the buck. There are a lot of things that need to be looked over relays, the main transformer which really isn't designed to run at those higher voltages also you metering lamps will burn out a lot faster etc...
@@hoosierbuy Thats why I said build a external power supply or you can up the caps in the amp. Anyway it all isnt really worth it anyway in the end better to get a bigger amp.
Drove the snot out of the 572bs to show what you you can get out of it. Shoulda bought the 811h will do 800watts with the stock tubes 572bs are more forgetful tube hearty mainly.
Ive seen these amplifiers with good 811 tubes with only 40 to 50 watts drive power easily produce 600 watts output from 160-15 meters and 550 watts output on 10 meters.
Yep... the 572 is definitely relatively stout. It has a maximum plate dissipation of 160 watts compared to the 811's max 65 watts dissipation. The 572 has a very rugged one-piece compressed graphite plate assembly for it's anode and the 811 has a stamped sheet-metal plate assembly made of two halves spot-welded together.. 572's are definitely an awesome and direct upgrade. :-)
Aren't you supposed to readjust the "Plate" and "Load" controls as you increase the drive? Also, makes no sense to increase the drive power past the point where there's no additional output power. Hope you don't leave it that way. At least that's the way I learned...
And you learned correctly. Turning it up past the point where power output does not increase is what causes non linearity. and yes the plate and load need to be retouched. 73 James K0UA
Plus at 450-550 watts 40-60 watts makes very little difference in the real world or in the wild $450 watts will be seen at the receiver station at the same as 550 watts, in other words just stick with the 450 watts with the drive both radio & amp will be happier . Big and better improvement over all run a 220 line in. The all will be happier. My 2 ¢ .
I recommend changing the power cord to a 12/3 or 10/3 power cord. Then put the bigger caps in it. The power cord they send them with are 16/3 which is not big enough to power a lamp much less a 811 3 tube amp.
That's the funniest thing I seen in a while - - you could put 4/3 power cord on - won't change a thing..... you shuold spend more time learning than posting and making yourself look uneducated.
This is an extra class operator, obviously that does not mean much these days.. just memorize the answers on the internet. He apparently has no experience with vacuum tubes and proper handling .You never, ever touch a vacuum tube with you bare hands, unless you want to create hot spots on the tube and decrease life expectancy of the tube. THIS VIDEO IS A PERFECT EXAMPLE OF HOW NOT TO REPLACE VACUUMS IN AN AMPLIFIER OR RADIO(and yes I remember the days when radios used vacuum tubes) Watch only if you need to know where tubes are located and how to remove. Do not follow this hams procedure.
@@lizzyfan1986 No, he told you correctly, you don't touch the tubes with your oily finger. You use rubber gloves. And you also retune when you increase drive significantly, and you never increase drive after the amp fails to increase appreciable power. The going to 85 watts to even test was a bad idea.
@@lizzyfan1986 No, he is not a "tool." He is telling it like it is. You don't touch tubes with your bare oily finger unless you want to shorten their lives. You also don't need to drive a 811 amp with more than 50 watts SSB unless you like replacing expensive tubes for no good reason. Like James Santore stated, we need to separate ham radio from CB. CB'ers focus on maximum power output and SWR. If the SWR meter shows 1:1, and output is max, all is good. A ham that understands what is going on knows that a 50 ohm resistor will give you a 1:1 SWR, and overdriving a tube or transistor amplifier will give you max output for a short duration, with maximum distortion, and short component life. You need a 6db increase in gain to achieve a 1 s unit of change at the receiving station. So driving an amp that chugs along happily at 450-500 watts to 600-800 watts does nothing for your signal, and simply shortens the life of your tubes/transistors. 6db gain requires a quadrupling of gain either from the transmitted power, or antenna. If you are S5 with 400 watts, you would need 1600 watts with the same antenna to gain 1 S unit. Hardly worth the cost of the amplifier components. Ignore the CB crap you have learned, and study actual radio math. Ray Jackson is correct. Anyone with a memory can become an Extra Class Ham.
So exactly how many minutes/hours/whatever does a quote “hot spot” from touching a tube reduce its life? Good grief. So the pair of 3-500z’s I installed with my bare hands 10 years ago, and still getting legal limit from by properly tuning and driving the amp, could fail any moment because I touched them with my old oily fingers?
if the Ht voltage is 1700v like 811a's require an 572B can never equal the power of the 811a at that set voltage... the 572B is more rugged and powerfull at 2400v HT. after each RF increase you need to dip the amp again. maybe the 811a\s were (soft) but i reckon they would have easily topped 600watt if dipped correctly, as i have never had them go weak, ratrher they go poof! if driven to hard due to heat failure of the anode shorting out on the grids (metal gas flakes of(redhot). so if you were to use the 572B's they will last forever as they will be used 60% of there capability running 1700v HT and not 2400v as they were intended. just my 5cents.. we all do as we please :)
A total waste of time and money. 572 has the same curve as an 811 except the voltage goes higher. Multiplication Factor of 811 is 160, 572 is 170. You have to increase the plate 1000 volts and pay more per tube for what? An extra 150 watts? And at what frequency? I rebuilt a Gonset 101 with a better HV supply and get more out of 811A without stressing the tubes.
