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Author Topic: AL-811 Newbie Questions  (Read 21565 times)
W6JHB
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« on: January 08, 2013, 04:29:09 PM »

Just unboxed and hooked up a band new AL-811. Driving it is an Elecraft K3/100. Behind it is an LDG AT-600ProII tuner (with M-600 meter), and the antenna is a 45-foot high 88-foot long doublet, fed with a 1:1 KW balun and 100+- feet of 450 ohm ladder line. I've come across two "issues".

I have three pieces of documentation on this amp. One was a manual downloaded from the Internet (this site, perhaps), one is the manual that came in the amp's box, and the third is a separate piece of paper that came with the amp. They have differing numbers when it comes to max plate current. The manual I downloaded from the web sez never exceed 700mA of plate current during tune-up. The manual in the box sez 600 mA, and the single sheet of paper in the box also sez 600 mA. However, the two manuals say to never have a plate current more than 450 mA. What's going on here? What is a safe number for these 811A tubes? If I try to keep the plate current at 450 mA, there is no way to get much more than 400 watts out. I CAN get close to 500 by running the Ip up to about 475-500 mA. Is this going to severely shorten the lives of those three tubes?

On 40-10 meters, it seems to load up pretty well and I can get close to 500 watts out (with the high plate current). However, 80 meters is a different story. I use an Inverted L on that band, and it has a 1:1 SWR. The problem here is that I have to turn the Load control all the way to zero to get a lot of output. The manual sez that's not good to do. If that's true, any idea why this only manifests itself on 80 meters?
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Jim / W6JHB
Retired in Folsom, CA - and loving it!!!
W6JHB
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« Reply #1 on: January 08, 2013, 04:55:41 PM »

Forgot to mention in the original post that I had called Ameritron support this afternoon. Before we got disconnected, the tech told me that all AL-811's after a certain serial number (including mine) has some new bias circuitry in it that allows more than 50-60 watts drive. He said that if need be, I could run up to 100 watts of drive w/o hurting the amp.
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Jim / W6JHB
Retired in Folsom, CA - and loving it!!!
W1NK
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« Reply #2 on: January 08, 2013, 05:36:55 PM »

Let me save you a lot of  tune up confusion and direct you to W8JI's AL811 tune up supplement.  Tom (if I recall correctly) designed the AL811 & 811H amps.  You'll see he specifically states that you should not exceed 550mA on the plate or 150mA on the grid during tuning or operation. http://www.w8ji.com/al811h_and_811_tuning_supplement.htm

Take it from a guy who has gone through his share of tubes because of improper tuning techniques, this is a real helper.   Wink

As far as the loading issue on 80M, this is due to the loading control needing an extra padding capacitor.  From what I understand you have to have additional capacitance at the loading control.  Check your amp's padding caps, you might have a 360 pF and a 500pF at the loading control.  If so, you have to add an additional 360pF padder in parallel with the 500pF.  This is discussed in this eHam thread: http://www.eham.net/ehamforum/smf/index.php?action=printpage;topic=73482.0

GL & 73

Frank, W1NK
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K4RVN
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« Reply #3 on: January 08, 2013, 06:09:46 PM »

Jim,
As Frank suggested use the link to read W8JI tuning supplement. As a three plus year owner- operator of the three tube 811 I would suggest that you tune with the CW mode part of Tom's post if you have no pecker. It is toward the bottom as you scroll down. I use only CW to tune and am still on the original tubes in my amp.
Also use about 20 watts or less to learn to tune, then use the steps to increase your power. You did not mention the mode or else I missed it. Use the presets say on 40 meters or higher band. Stay off 80 meters for the time being if you have to turn the load down to zero is my advice. That's really tough on the amp and tubes. I never exceed about 70 watts to drive my amp and you are asking for trouble if you exceed 100 watts. Also you are surely putting the hurt on your 811A tubes from what I read in your post. Don't try for 600 watts until you get to know the amp and can tune it in seconds. On ssb your amp meter readings will be very much lower than the values on tune up for the reasons Tom wrote. Use the presets as a beginning point, low drive, tune, cool down and peak the watts out on a watt meter. You will have to do it in several steps as Tom describes. Good luck. Your amp is probably in warranty so don't go working on it if it is, let Ameritron fix any problems
that are serious would be my advice.

Another Frank
« Last Edit: January 08, 2013, 06:14:50 PM by K4RVN » Logged
W6JHB
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« Reply #4 on: January 08, 2013, 06:25:34 PM »

Thanks for the links to W8JI's tuning info and the padding cap thread. I'll play around with the amp a little more on Wed morning. My operating is about 90% CW. Since it is a new amp, I "assume" it has the additional cap, but I'll pull the cover and take a look anyway. As to pushing it to max (550-600 watts) - I really don't need to do that - 500 watts out would suite me just fine. The additional couple watts aren't going to make much difference on the other end anyway.

I find it interesting that their manual indicates removing 12 screws to take off the cover. There are 16 - only removing 12 would NOT make one a happy camper! Cheesy
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Jim / W6JHB
Retired in Folsom, CA - and loving it!!!
WB2WIK
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« Reply #5 on: January 08, 2013, 06:36:41 PM »

If the LOAD control has to be at "zero" for maximum output, this might indicate a bad or insufficient padder cap on 80.

"Zero" on the control is maximum capacitance.
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K0ZN
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« Reply #6 on: January 08, 2013, 07:54:52 PM »

Hi,

I have an AL-811. Like you, I operate about 95% CW.  I had the exact same problem on 80 M CW that you are having.....load control went to zero on the low end of 80 M. What seems to be going on here is that the design/construction (choice of cap values on 80 m) apparently considered the amp to be for use ONLY on the SSB portion (75 m) from what I can tell; it appears they did not expect/design for CW operation. Same problem also existed on 160 M with my amp.  Looking inside the amp during operation, it was very easy to see that if operated in that condition it would over heat the tubes quickly; the plates got light orange hot quickly. i.e. way too hot.  Long story made short:  I had to go in and add some capacitance in parallel with the existing cap AND I had to move the tap on the tank coil a couple of turns (i.e. more L) to get it to load  and tune efficiently and properly on the low end of 80 M CW. It is still marginal on 160, but at the current time I have not modified it on 160 yet. Now, it will correctly tune on the low end of the 80 M band, but too much C to tune the upper part of the SSB band, but I don't operate there, so I don't care and I have another legal limit amp I can use there if wanted.

Let me caution you in the strongest terms that on CW, that amp will over heat/damage the tubes if you run much more than about 325 to 350 W of output. The cold fact
is that 811A tubes only have 65 watts of plate dissipation and cannot handle much more than that level with out over heating....and even that is pushing it. That
65 watts of plate dissipation is the ICAS rating. Those people pushing much more than that on CW are Waaaay in excess of the ratings on those tubes. Actually,
those ratings come from the old (and much higher quality) RCA tubes. From what I have seen and experienced, the current Chinese tubes do not seem to
have as thick metal in the plates and probably have less than 65 watts of plate dissipation. If you look at the plates during operation....which you absolutely
should from time to time..... you will see that they start to glow "too much" if you get much over about 300 watts of output on CW during a typical longer CW
transmission. To wit: a DULL orange glow is probably about the max. you want. If you get a "light orange" or very bright orange you are into the damage region in terms of heat. Typically, I can operate CW with about 325 W out and see only the slightest color in the tube plates and this is about what you want on an 811A in ICAS operation. The MFJ/Ameritron ad calls the 811A's "tough tubes"....actually, to the contrary....they are fairly fragile! Heed the warnings about limiting the grid current to 150 ma. 811A's do NOT have much grid dissipation and you can kill them in short order with excessive grid current. Keep the key down tuning time SHORT... seconds!! .... and allow
a little cool down time between tuning/tweaking periods.  Bottomline:  most of the damage to these amps is done by hams with lack of knowledge and/or improper
tuning techniques. If you are chasing DX and just making short calls and typical SHORT exchanges, I suppose you could push it to 400 W output, but if the DX station can't hear you with 350 W, he won't hear you at 400 either!

Lastly..... do not attempt to operate on 30 M !!  At least with my AL-811 the situation was worse than 80 M....the tank circuit and input was so mistuned that
it was obvious that it would kill the tubes in short order if I tried to use it on 30 M at the 200 W level. Basically, you have a CHOICE of EITHER 30M or 20M and a CHOICE of EITHER 15 or 17 M because the input circuit has to be tuned to one of those bands....it won't do both !!  At least, that is the way my AL-811 is. I ended up tuning
my amp for 17 M.

I went through a number of headaches with my AL-811 but finally got it straightened out.....you can read my product reviews here on eham.  I have had good luck
with it once modified, etc. and use it a lot as mostly what I do is casual rag chewing and could not see the point in firing up a couple of high dollar ceramic tubes just to chat. It is amazing what you can work with 300 watts....my experience is about 90% of what you can work with 1,500 watts ! ...at least on CW. If you only operate
it on SSB, which is about a 25% duty cycle and keep the power output to about 500 W, it is likely the tubes will last a long time. Data/RTTY service would be another
new world and the CCS ratings should be used!

My personal take is that they just carried the cost cutting too far on the AL-811.  IF... you understand what your really have and the LIMITATIONS of the
811A tubes and operate them WITHIN their published ratings, it will give good service...... if you push or abuse the tubes you are going to have a lot of problems.

"Your results may vary....."

73, K0ZN

« Last Edit: January 08, 2013, 08:00:22 PM by K0ZN » Logged
KF7CG
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« Reply #7 on: January 09, 2013, 10:41:34 AM »

I don't know for positive on the AL-811s but on the AL-811H that I run there is no problem running the amp on either 15 or 17, the input circuit is tuned in the middle. Further the input tuning within limits doesn't effect the life of the amp; mistuned input circuits cause trouble for the exciter and may cause some solid state rigs to go into high SWR power rollback.

The tuned input just makes it easier to get power from the exciter to the amp, it could be replaced with an appropriate network of resistors and be all band but would require large resistors and more drive.

KF7CG
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W6JHB
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« Reply #8 on: January 09, 2013, 10:49:27 AM »

So far it seems that 80 meters is the only problem with this unit. I pulled the cabinet off again and checked - it does have all THREE padding caps on the bandswitch. Rick from Ameritron asked me to call him back if I get the same result of Loading at zero when I drive the amp with 100 watts on 80. With 90 or 100 watts drive I can get 500+ watts of output, but the loading still goes to zero. I tried the amp on 160 and there is no "Load" issue there - only on 80 meters. On 160 I have to run the Tune control nearly to the full clockwise position for 450 watts out, but that's not a problem. Time to call Ameritron back.....
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Jim / W6JHB
Retired in Folsom, CA - and loving it!!!
W6JHB
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« Reply #9 on: January 09, 2013, 11:38:33 AM »

Just got off the phone with Rick at Ameritron. They are sending me a 360 and a 500 pf replacement padding cap. The engineer he spoke with said that perhaps the 360 in the amp is defective. I'm supposed to replace the 360 first and see if that resolves the issue. If not, pull the new 360 and put the new 500 in it's place, giving me two 500 pf caps in the unit. It looks like it'll only be a medium P.I.T.A. to get at those two caps.  Sad

Interestingly, I've got no problem on 160 - only 80 meters.

Is that "tuning pulser" worth the $65 - anyone using it here?
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Jim / W6JHB
Retired in Folsom, CA - and loving it!!!
W1NK
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« Reply #10 on: January 09, 2013, 12:43:33 PM »

Quote
Is that "tuning pulser" worth the $65 - anyone using it here?

I imagine you could achieve the same thing by setting your keyer to 30-40 WPM & using a good peak reading wattmeter

 Frank, W1NK
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K4RVN
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« Reply #11 on: January 09, 2013, 01:12:52 PM »

While you have the cover off, you might want to check where the 80 meter band  is tapped on the coil for future reference. I would suggest taking some digital photos to put on your computer for future use if your problem is not solved with the caps. Also make sure the band switch solder joints for 80 meters are good. In addition the padder cap grounds might be a good idea to check
while all the screws are out for the cover. Just make sure the power supply is discharged completely would be my advice. I don't see 160 loading OK if it is the padders, but I'm no tech and often wrong.
« Last Edit: January 09, 2013, 01:24:35 PM by K4RVN » Logged
WN2C
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« Reply #12 on: January 11, 2013, 08:13:25 AM »

After reading about the troubles with this amp, I think I will not buy one.  But I do have one question:  Are the 572 tubes better to use in this amp or do they have the same problems as the 811s

Rick  wn2c
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W8JX
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« Reply #13 on: January 11, 2013, 08:50:49 AM »

After reading about the troubles with this amp, I think I will not buy one.  But I do have one question:  Are the 572 tubes better to use in this amp or do they have the same problems as the 811s

Rick  wn2c

The 572's present a different problem of sorts. They are designed for higher plate voltages and currents and much higher plate dissipation than 811 too. When run at 811 levels in a 811 amp the plate/anodes may not heat properly to properly getter tube and remove air leakage in tube which is normal over its life span. It a 3 tube 811 amp you could run plates at higher current levels and likely get by but with 4 tube 811h there is no reserve in power supply for this (3 and 4 tube units use same power supply)
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WN2C
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« Reply #14 on: January 11, 2013, 09:04:32 AM »

AL-811HD HF AMP, 800W, (4) 572B TUBES, US 120VAC.  So if I read your reply correctly, then this amp from Ameritron should not work well either?  At $1250, it is a lot of money to spend on an amp that has "no reserve power left in the power supply".
Or am I reading into your last comment?

Rick wn2c
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