Posted: 4/11/2026 5:55:06 PM EDT
[Last Edit: Ramcharger_pilot][Edited]
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Amp has been stored 4 years, climate controlled. Haven't pulled the cover off yet. Anything I should check before plugging this in? I'm just a tech so I'll look for the green wire. Watching videos on tuning. Came with a manual. Thanks for any advice. Using a simple wire dipole in the trees, good enough? Have a diawa swr meter. ETA pictures. Attached File Attached File Attached File |
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I don't actually have that amplifier or any experience with it, and... I haven't owned an amp with 811A tubes since maybe 1972 or 1973. IIRC I swapped in some 572Bs back then, not that it necessarily made any difference, as I don't remember whether I made any power supply changes to accompany the tube swap. If it were mine, I might consider powering it up slowly, over some time, with a variac, before even considering driving it with rf, just to be sure that the electrolytic capacitors are happy. But maybe you will find more useful advice by reading through all of the old reviews from actual owners here: https://www.eham.net/reviews/view-product/220 |
Two guns, one bullet
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Run just the filaments on the 811s for a couple of hours before applying HV, then watched them closely. Depending on the brand of tubes in it, one or more may have a slight leak. Also, don't load it up to full output, go for about 3/4. The difference it will make in the received signal will not be noticeable. HINT: Raising or lowering the transmitted power by a factor of 4 will only change the received signal strength by ~ +/- 1 S-unit. ETA: I've had an AL-811 since the early '90s, put it away when I went to CW-only operation. Antenna was/is a homebrew trap/fan dipole, 80 thru 15 Meters. |
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Thanks everyone. It came with 2 extra tubes. No idea if they are matched. Looks like this was built in March and April of 2014 by the stickers. The seller just messaged, he found a 1kw dummy load and wants me to take it. I'll plug it in a let it sit a while. No hurry, 10 meters seemed kind of dead earlier. |
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Just be careful around the amp, the voltages are LETHAL ! The caps are probably fine, but I'd do as was suggested above. That is, bring the amp up slowly with a variac. If possible, run it on 240 VAC rather than 125 VAC. Learn to load it up quickly and safely, it reduces stress on the tubes. hth 73, Rob |
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Originally Posted By robmkivseries70: Just be careful around the amp, the voltages are LETHAL ! The caps are probably fine, but I'd do as was suggested above. That is, bring the amp up slowly with a variac. If possible, run it on 240 VAC rather than 125 VAC. Learn to load it up quickly and safely, it reduces stress on the tubes. hth 73, Rob My vote would be to throw in a dumpster and then buy a solid state amp like an Elecraft KPA500 or KPA1500. |
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| It has been a while, but I had an 811H the 4 tube model. I had a fair amount of trouble with it. Seems like it was D16 a diode in the metering circuit that failed a lot of times. These were standard 1 amp diodes. I finally replace it with a 3 amp diode and it solved that problem for good. The new set of tubes I put in it went "soft" within a year of FT8 operation. It really isn't made for FT8 operation. Maybe 200 watts. Will work pretty well on SSB and CW. I have a nice solid state amp now and will never own another tube amp. Two of the happiest days of my life was when I got my 811 and the other happiest day was when I sold it. |
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| If it was mine, I would power it up and tune it into the dummy load and test it out. It isn't that old. I expect it will work fine. As long as the tubes are good and the Meter diode isn't shorted. Be mindful of the power rating of the dummy load. Most are rated for very short periods of power. |
| No put the cover on to keep from electrocuting yourself or others. They are designed to run with a cover on and leaving it off is foolish. |
“Every man has two deaths, when he is buried in the ground and the last time someone says his name. In some ways, men can be immortal. “ - Ernest Hemingway
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Originally Posted By K9-Bob: No put the cover on to keep from electrocuting yourself or others. They are designed to run with a cover on and leaving it off is foolish. Ran about 10 minutes. Cover back on tomorrow. Need to hook up a ground wire before running anything but standby. More tomorrow or the next day. |
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Originally Posted By K9-Bob: No put the cover on to keep from electrocuting yourself or others. They are designed to run with a cover on and leaving it off is foolish. Sorry, I meant to say, if running for 20 minutes should I put the cover on. Just wanted to watch first startup. Didn't think that long would over heat on standby. |
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Just need a rca cable to trigger the amp. Thought I had one but quit looking. Run the ACL? I think not. I think this is the designer of the amp. I've watched a bunch of videos maybe its not. Lots of different ideas on how to tube. The dip, max power,or this video. https://youtu.be/ptWD2dTRi0g?si=ixZDxRw9bFkH50-L Going to pick up a rca cable tomorrow and give it a try. |
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Originally Posted By Ramcharger_pilot: Sorry, I meant to say, if running for 20 minutes should I put the cover on. Just wanted to watch first startup. Didn't think that long would over heat on standby. Understood. Just be very careful with the cover off. 
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“Every man has two deaths, when he is buried in the ground and the last time someone says his name. In some ways, men can be immortal. “ - Ernest Hemingway
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that amp looks like it has never been used or was cleaned very well recently usually those coils are tarnished from repeated hot and cold cycles I am surprised it turned on with the cover off, usually there is an interconnect switch that prevents operation with the cover off and will short the HV caps when you take the cover off. |
Mach
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Nobody is coming to save us.
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yep, the manual says that amp has a cover interconnect switch that removes AC power if you take the cover off. the previous owner may have disabled that if you didnt, be very careful also realize that just because the amp is off does not mean the HV is gone. Those caps can hold a lethal charge for a very long time. You must check for HV before you touch anything in that case. |
Mach
Nobody is coming to save us.
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Nobody is coming to save us.
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Originally Posted By Mach: yep, the manual says that amp has a cover interconnect switch that removes AC power if you take the cover off. the previous owner may have disabled that if you didnt, be very careful also realize that just because the amp is off does not mean the HV is gone. Those caps can hold a lethal charge for a very long time. You must check for HV before you touch anything in that case. Especially important if a bleeder resistor fails open. Don't assume around high voltage. VERIFY. |
| 1. Look up "Chicken Stick," on the internet. Order one or make one before you mess around with that amp. Someone has already defeated the safety device, don't become an unpleasant statistic! 2. Check for residual voltage at those large capacitors, that is where the voltage can be held for a long time. There should be large resistors very near by that are "supposed" to drain the volts away, do not trust them, VERIFY after using your chicken stick. |
Tuning video by the original engineer. Fast Carrier Tuning the 811H Amplifier Like others have said, do not operate a tube amplifier with the covers off, the voltage contained within WILL kill you. If you need to work on the amp, verify the high voltage meter goes to zero before removing the cover, when the cover is removed, ground the hv rectifier/capacitor bank AC input with a Jesus stick then apply a ground wire, do the same to the DC output of cap bank. If you have a little electrical altitude you can work on these yourself. Edit: quality parts are available here |
Middleofnowhere, Nebraska
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Originally Posted By tyrex13: Tagging to see if OP dies. ETA dibs on 811  I used an antenna clamp to hold down the safety switch. Only wanted to watch first power up in case something went wrong. The cover was replaced before testing. Will add tyrex13 to my will for the amp.  ETA picture Attached File |
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Originally Posted By Cordwood: 1. Look up "Chicken Stick," on the internet. Order one or make one before you mess around with that amp. Someone has already defeated the safety device, don't become an unpleasant statistic! 2. Check for residual voltage at those large capacitors, that is where the voltage can be held for a long time. There should be large resistors very near by that are "supposed" to drain the volts away, do not trust them, VERIFY after using your chicken stick. Thanks! |
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Originally Posted By FlatlandBusa: Tuning video by the original engineer.  https://www.youtube.com/watch?v=ptWD2dTRi0gLike others have said, do not operate a tube amplifier with the covers off, the voltage contained within WILL kill you. If you need to work on the amp, verify the high voltage meter goes to zero before removing the cover, when the cover is removed, ground the hv rectifier/capacitor bank AC input with a Jesus stick then apply a ground wire, do the same to the DC output of cap bank. If you have a little electrical altitude you can work on these yourself. Edit: quality parts are available here Thanks for the link. I posted a video above from the same person. Got as far as the diode check and both the grid and plate meters track the same so the diode is bad. ETA Looks like the same video. Emailed Tom for the fan upgrade and diode yesterday. |