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Author Topic: Ameritron AL-82  (Read 8155 times)
NT4I
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Posts: 17




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« on: November 27, 2012, 03:46:49 PM »

I read that the AL-1500, AL-1200 and AL-82 are completely identical except for the RF deck.
Can anyone validate this claim?
I am considering the AL-82 or the AL-1500 and completely ruling out the AL-1200.
I recently read the the new AL-1200 have the tube mounted and soldered in place.
Also, who knows what tube they are using now??? 3CX1200A7, 3CX1200Z7 or 3CX1200D7?
I suspect one can not go wrong with a pair of 3-500's or a single 8877.
Finally, how is the build quality on the current manufacturing of Ameritron amplifiers?

Or, do I bite the bullet and buy a new QRO HF-2000 or their new HF-3000 with the single 8877?
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W8JX
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« Reply #1 on: November 27, 2012, 07:09:12 PM »

While I have never owned a AL82 I have seen inside them a few times and they are fairly well built. They are one of the few 3-500z amps that actually use chimneys on tubes to help cool them and their sockets.  The only "bad" thing about it is that it takes a lot more drive to reach legal limit than a 8877 but 3-500's are a lot cheaper and pretty sturdy.
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K6AER
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« Reply #2 on: November 27, 2012, 09:08:44 PM »

I noticed at Dayton the power supply on the AL-82 was different with a smaller transformer than the AL-1200 and AL-1500. I repaired a AL-82 a few months ago and the amplifier was capable of about 1300 watts on most bands. It will not do legal limit. To have good SSB operation with a bit of head room I would run the amplifier at 1000 watts.
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9A4WY
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Posts: 23




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« Reply #3 on: November 27, 2012, 10:17:53 PM »

AL-82 will certainly do more than legal limit....but with higher drive(3-500Z EIMAC).If you have chinese tubes,they have higher gain and some people reports that AL-82 can do over 2000W Smiley??

With 120W and SN>1240 , on 40m and 20m you can get out all day long 1800W on CW and SSB(in dummy load of course).
73 9A4WY

« Last Edit: November 27, 2012, 11:15:18 PM by 9A4WY » Logged
K2DC
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« Reply #4 on: November 28, 2012, 03:20:12 AM »

It's been about 6 years since I had the AL-1200, and there have been changes since.  But I do know that at that time, the power supplies in the AL-1500, AL-1200 and AL-800H were all identical, and had some problems.  Mine (among others) was constantly blowing balancing resistors and internally arcing filter caps.  The balancing resistor problems were due to supplier issues, and the arcing filter caps caused by the blown balancing resistors compounded by a lack of design margin - The rated voltage of the caps was equal to the no-load voltage of the supply.

73,

Don, K2DC
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9A4WY
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« Reply #5 on: November 28, 2012, 04:24:24 AM »

that for the caps is right...0-10v margin for cap... Undecided...depends on mains voltage...not very good.
I reworked complete PS board and add 2 more caps...all caps are rated 400VDC so no load is abt 350-360V...plenty of safe margin... Wink
new board is same size, only difference is plastic board spacers(caps are too close to the spacers)
my old PS board worked, but I did not want to wait for spewing from blown caps all around PS compartment.
works like a swiss watch since  Smiley
73....Kristian
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WX7G
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« Reply #6 on: November 28, 2012, 04:45:24 AM »

AL-82, $2500 USD, eham reviews 4.8/5.0, 16 reviews

QRO-2000, $3500 USD, eham reviews 5.0/5.0, 37 reviews

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W1QJ
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« Reply #7 on: November 28, 2012, 05:14:31 AM »

NT4I, in the previous responses there are some good points suggested and some just plain wrong information.  First for the wrong information.  The Al-82 has the same transfoemr as the 1200 and the 1500, it is NOT smaller as suggested.  Someone threw the AL-800H into the mix and that amp does have a smaller transfomer for sure, but it is not in the discussion here.  It is NOT a "big box" Ameritron amplifier we are discussing.  The Al-1200 does not have a soldered in tube.  Lately the Z7 version of the 1200 series tube has been used.  The problem with the Al-1200 is that if the tube goes there are little or no reseasonably priced alternatives on the "pull" market.  3-500's are cheap enough to buy new when tube replacement is needed.  The 8877 tube is abundant on the "pull" market.  I prefer the Al-1500 to the three.  All 3 amps use the same transfomer and power supply components.  The RF deck section is pretty much all the same also.  The only real difference is the tubes and the filament transformeres and the 1500 has a 3 minute timer on the HV.  Even the input circuits are close enough to change out the tubes if desired.  I have taken many AL-1200's and Al82's and added an 8877 to them.  The real sparkling difference is in power output.  The AL-82 will do 1600 watts output with 100 watts drive.  The Al-1200 will do 1800 watts output with 100 watts drive and the Al-1500 will do 2300 watts output with 100 watts drive.  Maybe more.  You can see which amplifier has the most headroom when running 1500w (legal limit).  As one person pointed out if you have a high line voltage the HV can run VERY CLOSE to the total combined capacitor voltage.  This means the caps are being run to their limit.  Failures have occurred prematurely with caps and bleeders in these amps due to the lack of headroom.  The power supply really needs 10 caps, but the amp usually makes it through the warranty period.  It is quite easy to add 2 more caps if you are handy.  If you can stretch your budget to the 1500, that would be my choice.  You can save about 600 dollars if you go with the Chinese tube they offer as an option to the Eimac tube.  As far as the QRO amplifier goes, they seem to be very well built and I am sure is a very good amp especially the 8877 model.  I never owned a QRO amp since I am not a fan of tetrodes, but I would surely love to try their 8877 model.  Their construction looks very much like the Command Tech amps for obvious reasons.  Since I do repair work on trhe east coast for the legacy Command Tech amps I recognize the construction similarities but more so I am familiar with how the Commander amps work and they do work well.  I would put the quality of the Command and QRO a cut above the Ameritron!  Hope this helps.
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N4RSS
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« Reply #8 on: November 28, 2012, 06:38:52 AM »

The latest QRO-2000 runs 4000 volts on the plate Wink and has 10 capacitors.  Plenty of headroom over 1500 watts
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WX7G
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« Reply #9 on: November 28, 2012, 07:11:51 AM »

The QRO uses ten 400 volt capacitors for 4000 volts?
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N4RSS
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« Reply #10 on: November 28, 2012, 08:10:26 AM »

The QRO uses ten 400 volt capacitors for 4000 volts?

450 V according to their parts list
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WX7G
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Posts: 5908




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« Reply #11 on: November 28, 2012, 09:08:21 AM »

Ten 450 V caps at 4000 V is a bit close considering the tolerance of the balancing resistors and the leakage current of the capacitors affecting the voltage each capacitor sees.

This paper by CDE has a formula on page 12/13 for calculating balancing resistors.

http://www.cde.com/catalogs/AEappGUIDE.pdf


http://www.illinoiscapacitor.com/pdf/papers/reliability_of_capacitors.pdf

This paper by Illinois Capacitor details predicted capacitor life vs voltage. From 50% to 100% of rated voltage the life is inversely proportional to voltage. So, derating by an extra 10% only increases life by 10%. The reason to derate in a series string is to account for unequal leakage current and balancing resistor tolerance causing one or more caps to see excessive voltage.

There are electrolytic caps - even long life types - with ratings to 630 volts.
« Last Edit: November 28, 2012, 09:23:14 AM by WX7G » Logged
NT4I
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Posts: 17




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« Reply #12 on: November 28, 2012, 10:32:58 AM »

W1QJ
Thank you for your response as you answered directly to my questions.

Thanks to all others that took time to comment and voice your opinions and knowledge.

This was a great group of postings!

73'
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K0CWO
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Posts: 416




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« Reply #13 on: November 28, 2012, 02:33:07 PM »

Wholeheartedly agree with W1QJ.  I own an AL-1500 and it is good bang for the buck.  I almost bought an AL-82 but opted for a used HF-2000 because it has a muffin fan which is quieter than the squirrel cage fan in the big box Ameritron's.  My HF-2000 has eight 450 volt caps in it.  The change, and probably a good one, to ten 450 volt caps was made recently.  I don't think you can go wrong with either manufacturer.  Although the 8877 is a killer tube I wouldn't mind trying the AL-82 some day.  Something about glass tubes I guess.  It seems that every time you find something "pro" there is likely to be some "con".  I will say that QRO builds an amplifier like a brick crap house.  They are simple and the components, fit, and finish are excellent.

73, BJ 
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K1DA
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Posts: 460




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« Reply #14 on: December 05, 2012, 10:29:05 AM »

And thus we constantly hear the new breed running "15 hundret" watts to talk to a guy in the next state.
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