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Author Topic: Ameritron ALS-1300 Unpacking / Pictures  (Read 38235 times)
KD8MJR
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« Reply #90 on: March 13, 2011, 10:56:49 PM »


I never said they build crap, I did say that they over rate some of their products for marketing reasons. As I have said before I think their AL-82 is build like a tank and for about same money it is 2 or 3 times the amp a AL1300 is. And, on 811 amps, many have found out hard way that the 3 tube 600 watt rated amp it really a 400 to 450 watt unit and the 4 tube one is a 500 to 600 watt unit not 800 if you want it to last. Also I feel that AMeritron focuses on marketing so much that they cut corners. Example with 811 amp they brag how quiet it is and yet if they moved more air through it even at expense of a little more noise they would likely take abuse far better. Cooling is one place you never cut corner on in a amp.

On most of the Above I completely agree.
 If the ALS-1300 was made to be a 1000 watt amp it would probably be a good product, but they can't help themselves with this over rating stuff because they have gotten away with it for so long with their tube Amps. As you said, an ALS-811 is really a 450 Watt Amp, not 600 but hey if you overdrive the heck out of it you might get 600 watts for a few weeks before needing new tubes.

Even the Name "ALS-1300" is misleading!
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KD8MJR
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« Reply #91 on: March 13, 2011, 11:03:51 PM »

The mistake I keep seeing here is how folks are reading the MRF-150 datasheet. The mistake is thinking that the 150 watt RF output spec is set by reliability concerns. It is not. It is set by distortion product concerns.

Reliability is obtained by operating the device below the maximum ratings of 125 volts, 16 amps (continuous), and a junction temp of 200 deg C. Derating from these numbers will give higher reliability and an idea of how much can be found by using MIL-HDBK-217.

The ALS-1300 operates the devices like so when run with 50% duty cycle on-off keyed CW: 100 volts, 5 amps, and junction temp <45 deg C above the heatsink temp. When I measure the heatsink temp we'll know the junction temp. All of this points to good device derating.

Designing the amp for 1000 watts, rather than 1200 watts, would change these numbers to 90 volts, 4.8 amps, and 38 degrees.

What the heck are you talking about! It is also a Reliability Number!
Go out and buy a thousand MRF-150's and build a product that uses them at 160 Watts each and then have returns.  Call the Manufacturer and complain and hear what they will tell you. "No Money back on that one, you exceeded the Specs".
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WX7G
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« Reply #92 on: March 14, 2011, 06:47:02 AM »

No, 150 watts is where it operates with low enough distortion. It is not even a spec, it's in the component description.

Look at the Motorola datasheet figure 4 and you will see the IMD starting to deteriorate quickly above 150 watts. Figure 3 shows the components beginning to saturate at above 150 watts. This is what establishes the recommended 150 watt operating point.

A manufacture guarantees and tests the MIN and MAX specs on all units. This part has no spec for maximum output power. This part is tested for drain voltage, drain current, gate threshold voltage, transconductance, drain leakage current, gate leakage current, and die attach (a transient thermal test).

I designed MOSFET test equipment a couple of jobs ago. Before, during and after that job I designed power electronics. I would have no qualms designing with this component running 150 watts output in continuous commercial service, 24/7 for years on end. The one spec I would derate is junction temperature. I would keep the junction temp well below 200 deg C, perhaps as high as 150 deg C. The thing to watch out for is the junction temp during transient events (shorted antenna for example, or a transceiver over driving the amp). The junction temp will rise during such an event before the protective circuitry can shut things down. The steady state junction temps must be limited such that the peak temp during a transient remains (well) below 200 deg C.

How hot does the junction temp get in the ALS-1300 during a transient event? Might this be the Achilles heal of the ALS-1300?

In amateur service no one really runs continous duty and this part has an easy life. Blindly applying component derating leads to expensive and uncompetitive designs. As for reliability, don't exceed any maximum specs for even an instant and a part will last.






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K2ACB
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« Reply #93 on: March 14, 2011, 08:03:35 AM »

I have never owned an Ameritron Amplifier. However I have owned three Tokyo Hy Power HF Amplifiers.I sold one of them to buy a larger Tokyo Hy Power Amplifier.  I have never had any trouble with them.

The service of Tokyo Hy Power is excellent.Yes, their solid state amplifiers cost more than Ameritons.However, in general ,the ratings of Tokyo Hy Power amplifiers in the product Review section of E Ham.Net and  compare complaints about Tokyo Hy Power solid state amplifiers and those of Ameritron. You will see there is a difference in favor of Tokyo Hy power.

Some say you get what you pay for.It is not always the case that you get better quality in a product if you pay more for it. However this seems to be the case when you compare solid state amplifiers made by Ameritron as compared to Tokyo Hy Power.

It has also been pointed out that Tokyo Hy Power as well as Yaesu and Icom that have solid state amplifiers using eight MRF 150 FET'S rate them conservatively at 1 kw instead of rating them as 1200 watt amplifiers.

Whenever you buy products from MFJ you take a chance on their quality control.Some of their products have been very good while other products have had poor quality control. They have also been criticized for the slow repair time they have taken on some of their products including their solid state hf amplifiers.

That is not to say that MFJ and their subsidiary Ameritron make inferior products. Many radio amateurs are satisfied with them including a lot of Ameritron hf amplifier owners.

However,especially in the case of solid state amplifiers, if you want to buy a superior product where most owners are very satisfied with their solid state amplifiers, I would consider spending the extra money to  buy a Tokyo Hy Power amplifier than one from Ameritron.

73
Alan-K2ACB
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WX7G
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« Reply #94 on: March 14, 2011, 11:12:12 AM »

I agree, no doubt the THP amps are better.

The derating to 1 kW or less would be great for improved IMD. Even 1 kW is pushing things when driving a low impedance load. The MRF-150 datasheet shows IMD starting to climb fast at 150 watts. Remember, this is into the correct load impedance. When running the ALS-1300 into a 1.5:1 VSWR (33 ohms) on the low side of 50 ohms device current is increased by 23% and the IMD will then be similar to what the datasheet shows for over 200 watts.

Since I run CW only this isn't as much of a concern and I should be able to safety and cleanly run the amp at 1500 watts.
« Last Edit: March 14, 2011, 12:12:26 PM by WX7G » Logged
KD8MJR
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Posts: 2079




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« Reply #95 on: March 14, 2011, 04:05:40 PM »

No, 150 watts is where it operates with low enough distortion. It is not even a spec, it's in the component description.

Look at the Motorola datasheet figure 4 and you will see the IMD starting to deteriorate quickly above 150 watts. Figure 3 shows the components beginning to saturate at above 150 watts. This is what establishes the recommended 150 watt operating point.

A manufacture guarantees and tests the MIN and MAX specs on all units. This part has no spec for maximum output power. This part is tested for drain voltage, drain current, gate threshold voltage, transconductance, drain leakage current, gate leakage current, and die attach (a transient thermal test).

I designed MOSFET test equipment a couple of jobs ago. Before, during and after that job I designed power electronics. I would have no qualms designing with this component running 150 watts output in continuous commercial service, 24/7 for years on end. The one spec I would derate is junction temperature. I would keep the junction temp well below 200 deg C, perhaps as high as 150 deg C. The thing to watch out for is the junction temp during transient events (shorted antenna for example, or a transceiver over driving the amp). The junction temp will rise during such an event before the protective circuitry can shut things down. The steady state junction temps must be limited such that the peak temp during a transient remains (well) below 200 deg C.

How hot does the junction temp get in the ALS-1300 during a transient event? Might this be the Achilles heal of the ALS-1300?

In amateur service no one really runs continous duty and this part has an easy life. Blindly applying component derating leads to expensive and uncompetitive designs. As for reliability, don't exceed any maximum specs for even an instant and a part will last.



And I would repeat, go out and buy a thousand MRF-150's and build a product that uses them at 160 Watts each and then have returns.  Call the Manufacturer and complain and hear what they will tell you. "No Money back on that one, you exceeded the Specs".
I understand what your saying but as you state the FET is at or near Saturation at 150W and no matter how you slice it the company will not warranty the product if you go out of Spec and there's a good reason for that.
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WX7G
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« Reply #96 on: March 15, 2011, 12:46:34 PM »

You still don't understand that the 150 watt blurb is not a spec.

It is there only to tell you that in class AB push-pull service with 50 volt rails 150 watts is about the maximum you should shoot for if linear amplification is the goal. In class-C service I suspect 300 watts or more output can be had without stressing the part.

The manufacturer doesn't care how much power output you are running if no MAX specs are violated. The specs that matter to a manufacturer are MIN and MAX specs. Don't exceed those and you are not abusing the part.

When a dead MOSFET is returned to a manufacturer they will decapsulate it and determine exactly what overstress killed it. And be assured that if a part dies it is not a defective part. With 100% testing of all MIN/MAX specs and test guardbands defective parts are virtually unheard of these days. Many manufacturers aim for a rate of just 1 PPM defective parts shipped. Dead parts point to abuse of some sort.
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KD8MJR
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« Reply #97 on: March 16, 2011, 03:55:48 PM »

You still don't understand that the 150 watt blurb is not a spec.

No I give up, this thread will go on forever.

http://www.datasheetcatalog.org/datasheet/motorola/MRF150.pdf

People can read the Datasheet and make their own conclusions, people can also look at the amount of Blown up ALS-1300 Finals and also make their own decisions.
« Last Edit: March 16, 2011, 03:57:55 PM by KD8MJR » Logged
N8YX
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Posts: 111




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« Reply #98 on: March 24, 2011, 08:48:56 AM »

Page 3, Fig 3 of that PDF shows a single-device PO of ~210w at 30MHz with 50VDD.

Assuming the device is being operated in Class C - and assuming 75% efficiency - 1300w single-tone output spread amongst 8 devices is well within the single-device ratings.

Further:

If - using the PO Max values above - we scale back the efficiency to 66% (AB2), we get a total output of ~1400w with 8. Factor in 700w of dissipation and you get ~2100w input power. The per-device maximum ratings are spec'd at 300w, so 8 of them would yield a 2400w maximum.

The amplifier does not appear to be exceeding Motorola's published specifications even at full output.

I would suspect a load-balancing/matching problem with the output networks long before I would suspect that the amp is being run beyond device maximums. And this could be tied to construction practices.


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W8JX
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« Reply #99 on: March 24, 2011, 12:34:01 PM »

Page 3, Fig 3 of that PDF shows a single-device PO of ~210w at 30MHz with 50VDD.

Assuming the device is being operated in Class C - and assuming 75% efficiency - 1300w single-tone output spread amongst 8 devices is well within the single-device ratings.

Further:

If - using the PO Max values above - we scale back the efficiency to 66% (AB2), we get a total output of ~1400w with 8. Factor in 700w of dissipation and you get ~2100w input power. The per-device maximum ratings are spec'd at 300w, so 8 of them would yield a 2400w maximum.

The amplifier does not appear to be exceeding Motorola's published specifications even at full output.

I would suspect a load-balancing/matching problem with the output networks long before I would suspect that the amp is being run beyond device maximums. And this could be tied to construction practices.




Where in the heck are you getting 75% efficiency at?Huh? Those devices struggle to get close to 50%. I do find it interesting how manufacture rated 150 watts devices are be portrayed as being far sturdier. Solid state (unlike a tube) is very unforgiving and it will fail when pushed. If these finals and amp where as robust as suggested they would not have the failure rate they do. You get what you pay for here.
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K7KB
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« Reply #100 on: March 24, 2011, 03:58:05 PM »

You can argue design specifications until you are blue in the face. It might be the best designed amplifier in the world, but if it uses sub-standard parts or is poorly constructed the failure rate will still be unacceptable.

John K7KB
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KD8MJR
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« Reply #101 on: March 24, 2011, 04:57:51 PM »

75% Efficiency LOL !  That kind of post is exactly why I gave up with this Argument.
People don't really understand this stuff and they make assumptions based on what they think is correct.  That's why Ameritron is able to pull so many people into the hype even though they are showing exactly whats in their Hands.  When I got my THP 1.2kfx the first thing I did was check out the PA board and what it had. When I realized they had 1200 Watts of FETS being used in a Amp specified as a 750 Watt Amp, I was sold, it speaks volumes to how they must be specking everything in the Amp.  That's why to me it no surprise I can pull 1KW out of it, I just choose not to do it on a regular basis.

Where in the heck are you getting 75% efficiency at?Huh? Those devices struggle to get close to 50%. I do find it interesting how manufacture rated 150 watts devices are be portrayed as being far sturdier. Solid state (unlike a tube) is very unforgiving and it will fail when pushed. If these finals and amp where as robust as suggested they would not have the failure rate they do. You get what you pay for here.
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N8YX
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« Reply #102 on: March 25, 2011, 04:55:34 AM »

Where in the heck are you getting 75% efficiency at?Huh? Those devices struggle to get close to 50%.
I went back to the linked PDF and read through it again. We see a "typical" drain efficiency of 45% but not a "max".

Missing is the class of operation in which the device was run to obtain that figure. In all likelihood it's Class AB. The same device in Class AB2 or C is going to yield a higher efficiency. How much more is anyone's guess, as Motorola didn't publish the figures. It was that theoretical maximum (and a practical maximum in AB2) upon which I based my figures.

(Edit: Tom, 'JI's earlier comments WRT observed output power tend to substantiate my figures.)

On paper, 8x MRF150s should absolutely be capable of 1200w PEP out with the 45% efficiency rating you quoted. If they're failing in real life when operated at this power level, I still lean towards improper load balancing and output coupling as the reason. Maybe cooling, but no one has remarked that the amp seems to get overly hot.

With the quoted efficiency figures, push them very much higher and all bets are off. But I'm thinking that Ameritron designed a bit of headroom into the operating parameters, possibly at the expense of IMD.

I'm not defending Ameritron here - just offering some thoughts about what might be taking place. And why.

« Last Edit: March 25, 2011, 05:07:41 AM by N8YX » Logged
N8YX
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« Reply #103 on: March 25, 2011, 04:56:21 AM »

75% Efficiency LOL !  That kind of post is exactly why I gave up with this Argument.
...and you're still here why?

By your own words:

Quote
"...Look I am no expert on Amplifiers..."
Tom, W8JI is.

If he says the device is capable of the power output which Ameritron claims, you may take that to the bank.

This of course assumes the assemblers did their jobs correctly.
« Last Edit: March 25, 2011, 05:05:15 AM by N8YX » Logged
W8JX
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« Reply #104 on: March 25, 2011, 06:18:59 AM »

Being capable of doing it in short term is one thing while being able to sustain it long term is quite another.
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