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Author Topic: AL-811H Lost Plate Current  (Read 13566 times)

Posts: 442


« Reply #75 on: August 16, 2016, 07:22:46 PM »

Maybe the AL-811H is "Over-Rated" by the manufacturer as to it's output power. Maybe PEP SSB isn't anywhere close to 800 watts. Maybe it's closer to 500-550 watts like a 30L1 amp. Now, we recognize that the power supply between the 30L1 and the AL-811H are different. But the 30L1 instructions show input tuning between 70-100 watts. Whereby the AL-811H says PEAK output is usually achieved with an input wattage of 65 watts. Now I am VERY familiar with the 30L1. 21 years in the military, with 15 of those years working on more kwm-2a and 30L-1 and S-1 than I can count. So to say that the 811A tube totally sucks, is pure bull shiite.


Hi Mike,

Have no Armadillo in the race and won't comment on the 811 series tubes.

I do have some observations and questions regarding the AL-811H.

Your comment regarding the power supply differences between the 30L1 and AL-811H are notable.  Not that the 811H is under rated or inferior in power capabilities.  But the filter capacitor stack seems three times higher than I would expect and don't see a surge resistor.  With the capacity at 50uf and the absence of a surge resistor any short or flash over will evaporate something.  The 30L1 power supply provides a higher level of protection for that.

The drive difference between the 30L1 and AL-811 is a result of the grid circuit design.  The 30L1 implements negative feed back whereas the AL-811H grid circuit design nearly totally removed the negative feedback function.  Someone mentioned that the designer has recommended removing what little negative feed back there was by grounding the grids.

Two things to note.  If you are accustomed to driving the 30L1 and expect to use the same drive power in the AL-811H you will smoke it.  This I believe is compounded by the lack of adequate protection by the power supply.  If a tube should overheat, short, or flash over, things will evaporate.

I'm certainly not trying to rain on the AL-811H design just mean to say it needs to be pampered a bit more than the 30L1.  Don't see any reason to believe it will not serve you well --- just needs more care than folks are accustomed especially if they are accustomed to the 30L1.

A great day to you and have fun with that radio. 

Kindest regards Jim


Posts: 1016

« Reply #76 on: August 16, 2016, 08:34:12 PM »

I did decide however that I'd rather put in a NEW Plate Choke. I can keep the existing one as a backup if needed. The Plate Choke shipped and I should receive it before the weekend. While at it, I bought a new style parasitic compressor as well as 4 new HV capacitors and 4 divider resistors. The cost for these replacements/upgrades is only about $120, so I think it's worth the effort and expense.

I'm all for fixing what's broken and it's great that MFJ/Ameritron has all the spare parts readily available.

And I'm a huge fan of the AL-811H. It's a great value, easily maintened, the Chinese 811A's are more durable than most give them credit for, etc.

But... you gotta be careful. Buying $100+ worth of "upgrade" parts for an already working amp when a complete working used 811H amp has a street price of $400 (used) is a little odd, when maybe you should be saving up for a bigger amp.

N3QE. Thanks for the feedback. I appreciate what you're saying. But I'm not worried about spending $120 in some parts.
1) If you can find a good working 811H for $400..... BUY IT. Buy more if you can. The going price generally, used, will be in the $600-$650 range. Of course, you could find one at a ham fest or something cheaper. But generally speaking, it is around $600-$650.
2) I definitely don't need or want to buy a "Bigger Amp". Power wise, this is about the biggest any of my house circuits can handle. I'm not going to spend well over $1000 to put in a bigger 120/240 circuit. The wife would never allow the construction needed. What I have now for electrical, I'd be pushing if I had a bigger amp. Plus, I already have an old Swan. Works, an FL-2100B (Has some issues, but I use to use it a lot. I can fix it if I want), and an ALS-500 Solid State 400/500w amp. The ALS-500 is what I used to use most times.
3. I bought this AL-811H because my friend needed to sell it; I wanted an amp that had a bit more power that my electrical could handle; and because he sold it to me at a really good price. Much better price than I could buy it for normally.

Thing is, the AL-811H is a decent amp. Is the greatest? Nope. But it's pretty good. I just get pissed when people write, especially negative comments, as if they are the authority on the matter. They aren't. And if the AL-811H really was that bad, they wouldn't still be selling them 25 years later. You yourself recognize that it's a pretty decent amp. As for me spending $120 on parts.... Well, I'm fortunate enough where $120 doesn't really mean that much to me. I just happen to like the technical side of radios more than talking on them. If all I wanted, was an amplifier to get online with and talk, I could spend $6000-$7000 on an ACOM and be done with it. And honestly, my wife probably wouldn't even notice the change in the bank account. I'm fortunate financially.

But there's a few minor little quirks with the AL-811H I bought from my friend. I've only had for about 6 months. It's a decent amp. I had planned on replacing the parasitic and the caps one day anyway; so I figured why not now being I have to order the Plate Choke anyway. This same friend, sold me he ICOM IC-718. A couple years old, but almost never used. He sold it to be for $250. Not my favorite transceiver, but it's fun to play with. (Which by the way, is what STARTED this thread. Adapting a dynamic mic (yaesu) to work on the IC-718. When I heard a friend on air, I didn't reset anything in the radio. I turned on the AL-811H and shoved it with about 100+ watts, 100% mic gain, compression, and some other settings I can't remember). Basically, once I keyed the radio and the amp said "Bite Me", I sort of knew what I had done. Funny thing is...... those supposed CRAPPY 811A (In my case G-811 Ryazan) tubes didn't even blink. They didn't pop or die. Not bad for a crappy tube. Still putting out the same amount of power after the repair as before.

Anyway, that's why I don't mind spending money on parts. It's fun. I don't need a new or bigger amp. I have more than enough; and more than my electrical can handle. But this fun.

On a side note. After most of today's posts on this thread, I was speaking to a friend of mine out of state. He sort of owes me a favor or two. He has 4 brand new (New Old Stock) Taylor 572b tubes. Still in box, never used. He doesn't need them. He's had them forever. He's sending them to me to play with. I'll give them a try in the AL-811H. Not sure if I'll notice anything, but I'll see if they operate OK. He said if I like them, I can keep them. If not, I'll send them back to him. I've used 572b before in SB200 and the Fl2100B. Just never tried them as a replacement for the 811A. I'll give it a try.  
« Last Edit: August 16, 2016, 08:39:33 PM by WY7CHY » Logged

Born Wild - Raised Proud: 73
Cheyenne, Wyoming
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