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Author Topic: Ameritron AL-811 problem  (Read 2151 times)
AC4R
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Posts: 18




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« on: November 17, 2007, 05:24:13 PM »

I have an AL-811 one year old in Sept. In July when i turned it on the relays chattered the grid current meter barley moved and the amp went dark. This was just after turning it on to warm up it was not in the operate mode. I sent it back to Ameritron who repared it and replaced 3 tubes , they said two were shorted and one was burned , they also replaced two fuses and a diode. It did the same thing again last night. Is this a common problem with the AL-811 ?  If is going to be a continuing problem i dont want to keep playing the game with this amp. It is now out of warranty i am trying to decide if i should send it back again, or just junk it out .

AC4R
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WB2WIK
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Posts: 20537




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« Reply #1 on: November 17, 2007, 07:00:51 PM »

No, that is not a common problem with the AL-811 at all.

If Ameritron did the last repair they should have issued a new warranty based on the date of the repair.  If they installed tubes in it and the tubes have shorted and damaged the amplifier, they should repair it for free.

NOT a common problem -- tens of thousands of hams have AL-811s with zero problems.

WB2WIK/6
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W5RKL
Member

Posts: 888




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« Reply #2 on: November 18, 2007, 09:12:36 AM »

I had a problem last year with my AL-811. I purchased
it brand new form R&L Electronics in Hamilton Ohio
and after 4 months, 2 of the 811's developed vacuum
leaks causing them to fail. Ameritron's customer
service wanted me to ship the tubes back them so
"they" could determine if the tubes had failed. The
guy at customer service was an idiot so I went up
the food chain and spoke with Mike Enis, a supervisor
at Ameritron. After I explained everything to him, he
said, "we'll pay to ship your amplifier back to us.
Package it up in the original box and I'll send you
the UPS shipping account number." They did just that
and within a week I had a brand new amplifier.

Here's Mike's e-mail address or you can call
Ameritron and ask for him.

"Mike Enis" <menis@ameritron.com>

Hopefully he still works for Ameritron. I can't say
for sure you'll get the same result but it's worth a
try. Make sure you have all the documentation
including the repair docs. Without them, they may
not be able to do anything.

73's
Mike
W5RKL
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WD8PTB
Member

Posts: 671




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« Reply #3 on: November 18, 2007, 11:10:28 AM »

When the 811 shorts it normaly takes a grid resister (51ohm) and one or both fuses. Many of the early 811's from China were prone to this problem. I eventualy (after replacing 3 tubes/fuses/resisters) put 572 B's in mine. Never had a problem after I changes to 572B's.
   Many people will tell you that the 572B needs higher voltage etc. While they may be technicaly correct. They worked fine in my amp (811H) and I have talked to several other hams who did the same. None had any problems with the 572B's and none got bad signal reports with the 572B's.
   There will also be others that suggest that the 572B's won't be linear. The truth is how you tune it up has a lot to do with linearity. Ther are many amps out there made by various Builders and they are all capable of "splatter" if tuned up wrong. 73 WD8PTB
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K6AER
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Posts: 3468




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« Reply #4 on: November 18, 2007, 05:11:42 PM »

The 572B’s are just as linear as 811A’s. How a tube is biased and loaded determines the linearity.

You need higher voltage if you want more power out of the 572B’s tubes. You cannot put 811A’s in place of 572B’s. The tubes don’t have the dissipation or the voltage rating.

You can put the 572B’s in place of the lower dissipation rating of the 811A’s. They will not give you one watt more power but they have a higher dissipation rating.

Typical voltages and wattages listed below.

811A,   1500 volts, 65 watts dissipation

572B,    2750 volts, 185 watts dissipation.
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WD8PTB
Member

Posts: 671




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« Reply #5 on: November 20, 2007, 06:19:19 AM »

That is correct 811/572B will give the same power. I was able to get a little more  because the 572B's will take more grid current. I also noticed that the tuneing was slightly different, not much but a little. WD8PTB
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AC4R
Member

Posts: 18




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« Reply #6 on: November 21, 2007, 05:34:11 AM »

Thanks for all of the help on my amp.  After talking to others they also say the 811 tubes have a track record of causing problems. I am ordering 3 matched Svetlana 572B tubes from RF Parts to replace the 811s and will go from there. From everything i have read the Svetlana seem to be the best tube going and should be a plug and play type for the Ameritron AL-811. I am not looking to get more power out, just want something that will last longer than 90 days.

AC4R
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W5RKL
Member

Posts: 888




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« Reply #7 on: November 22, 2007, 02:41:06 PM »

"Matched pair of 572B".

hmmm....I've done that and found it was a huge waste
of money. I seriously doubt you will be able to tell
one tube conducting slightly less than the other
in a new set of unmatched tubes.

Where's this "811's are bad tubes" syndrome coming
from? I'm not saying there aren't tubes that fail
due to a bad batch. But to ear mark 811's as being a
bad tube is simply nonsense! Yeah, I've read "My buddy
has a.... and it blew both tubes after trying to
load up a bed spring and...", "I heard a guy that ran
a ... and it...after 48 hours of..", and "I had a 1.5
Jigawatt Cloud Burner amp that...and I was told that
the tubes were bad..." type reports. I often wonder if
some of the complaints are due to plain old operator
error caused by not reading, understanding, and
abiding by what is said in the equipment manuals!

73's
Mike
W5RKL
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WD8PTB
Member

Posts: 671




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« Reply #8 on: November 23, 2007, 05:29:21 AM »

The 811 is not a "bad tube" but most of them are now made in China. The early tubes made in china had a tendency to short grid to fillament. It is difficult to get 811's that are NOS (new old stock). If you can find them they are more expensive.
   I have personaly replaced the 811's with 572B's and have talked to 2 other hams who did the same. In all cases they were "plug and play" with no modifications and no problems. 73 WD8PTB
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W3LK
Member

Posts: 5644




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« Reply #9 on: November 23, 2007, 06:49:30 AM »

A contributing factor is the tendency of many owners of the 811 and 811H amps to overdrive them, trying for every last watt of output. This often results in premature tube failure when the dissipation ratings of the tubes are exceeded.

73,

Lon - W3LK
Naugatuck, Connecticut
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A smoking section in a restaurant makes as much sense as a peeing section in a swimming pool.
WI7B
Member

Posts: 53


WWW

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« Reply #10 on: November 29, 2007, 02:17:19 PM »


I have a different take on this same symptom you describe.

My AL-811 followed the same pattern asyours.  It blew one, then both fuses.  The lights would flicker and the relays would chatter.

I replaced the fuses and did a thorough dusting of the insides, and cleaning and re-seating the tubes  (as they cycle through warming and cooling they can become loose in their sockets).  After this dust-off, I have had few problesm.  

Ameritron replaced all three 811As?  I haven't replace one in over three years of owning the amp, although I have replaced 4-5 fuses because of dirt.

73,

---* Ken
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K7RNV
Member

Posts: 98


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« Reply #11 on: December 03, 2007, 10:43:13 PM »

keep the amp, it is a work horse...you just keep getting bad tubes..73 bob
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