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Author Topic: Ameritron ALS1300  (Read 2231 times)
K8OT
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« on: February 21, 2010, 06:19:07 PM »

Just got an ALS1300 and had a problem with PA lite coming on. evidently one of the power FET blown. anybody else have any problems of any kind?
It is at Ameritron being repaired.
K8OT
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W8JI
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« Reply #1 on: February 22, 2010, 03:17:13 AM »

Just got an ALS1300 and had a problem with PA lite coming on. evidently one of the power FET blown. anybody else have any problems of any kind?
It is at Ameritron being repaired.
K8OT

Sounds like one PA module is dead or has low gain. That could be almost anything from a dead power supply to a splitter or combiner issue. I wouldn't think it is an FET because they have thermal foldback and other protection. My 1300 is running well with my K3. I'm hammering it pretty hard at 1500 watts output on CW, but only running 1200 PEP on SSB. I'm having a hard time getting used to instant on power and an amplifier tucked out of the way off the operating desk. :-)
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W9OY
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« Reply #2 on: February 22, 2010, 01:14:42 PM »

Mine came with one of the power supply modules loose and a nut rattling around.  Once you get it working you will love this amp.  I have mine set up to band follow my transceiver, and I use it for search and pounce when running SO2R.  

Nice to know it will run 1500 on CW without loosing its mind

73  W9OY
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N0AZZ
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« Reply #3 on: February 22, 2010, 02:28:20 PM »

Had one for a month did not care for it sold and bought another VL-1000 Yaesu for my backup amp.  

Fred  N0AZZ
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K8OT
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« Reply #4 on: February 22, 2010, 03:58:41 PM »

Good to know. I was starting to wonder if I made a mistake. In the two days I had it I never ran over 1000 wts the voltage on both power supplys were with in a couple volts It would run up to300 wts but kick out at 350 and the mismatch got high. John at Ameritron said one of the transistors went and they had to replace all eight because they had to match.
I hope I don't have anymore trouble becaust I think I'm going to like it. do you run ALC??
I think I'll get the remote so it will follow the Rig (Yaesu920) that sounds like a winner.
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K8OT
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« Reply #5 on: February 22, 2010, 04:08:45 PM »

Good to know. I was starting to wonder if I made a mistake. In the two days I had it I never ran over 1000 wts the voltage on both power supplys were with in a couple volts It would run up to300 wts but kick out at 350 and the mismatch got high. John at Ameritron said one of the transistors went and they had to replace all eight because they had to match.
I hope I don't have anymore trouble becaust I think I'm going to like it. do you run ALC??
I think I'll get the remote so it will follow the Rig (Yaesu920) that sounds like a winner.
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W8JI
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« Reply #6 on: February 22, 2010, 07:36:55 PM »

Good to know. I was starting to wonder if I made a mistake. In the two days I had it I never ran over 1000 wts the voltage on both power supplys were with in a couple volts It would run up to300 wts but kick out at 350 and the mismatch got high. John at Ameritron said one of the transistors went and they had to replace all eight because they had to match.
I hope I don't have anymore trouble becaust I think I'm going to like it. do you run ALC??
I think I'll get the remote so it will follow the Rig (Yaesu920) that sounds like a winner.

There are some mods they have to do to the transistor mounting screws and washers. They are changing to hardened steel screws instead of stainless and using hardened washers. Also two resistors change to 27k from 10k. Make sure they do that. :-)

I'm hammering mine at just over 1500 watts on CW but I put those mods in mine this weekend. So far so good. No ALC on mine.







.
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K8OT
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« Reply #7 on: February 23, 2010, 05:08:01 AM »

Tnx fer the info, I hope when they replace the transistor screws they put in the steel ones, I think stainless has higher expantion.
Where are the 10k resistors located, I can't seem to locate them on the schematic?
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W8JI
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« Reply #8 on: February 23, 2010, 07:27:24 AM »

Tnx fer the info, I hope when they replace the transistor screws they put in the steel ones, I think stainless has higher expantion.
Where are the 10k resistors located, I can't seem to locate them on the schematic?

On CB1, I think R48 and 50. I'm not sure though. They are the pull down resistors on the base of the bias voltage regulator.

The problem with the stainless screws is something changed at the vendor (probably went to China) and they stretch when torqued, not heat.
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K8OT
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« Reply #9 on: March 24, 2010, 10:57:58 AM »

Had it back from Ameritron for a while now and it's working fine.
  It sure feels good to have more power on 160 now for DX
one thing I found, on my old Johnson thunderbolt, I ran it at 1 KW in (the old rule) and it put out 600 wts. But no 160 the ASL1300 will put out 1200 wts, But so far I run it at 1 KW out. and have no problems in the pile ups. Now to work on my receive antennas!

ED K8OT
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NN4X
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« Reply #10 on: April 03, 2010, 08:09:57 AM »

Tom -

1,500 watts?  The MRF-150 is rated for 150 watts.  There are eight in the ALS1300, so...let's see...carry the 4...looks like 1,200 watts is the max output.

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

Is it worth pushing them so hard?  It looks like the IMD products go up pretty rapidly after 120 watts or so.

Just curious; you're the guru. (LOVE your website, BTW - I reference it all the time.  THANK YOU!)  :-)

73,

Steve
NN4X
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K6AER
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« Reply #11 on: April 03, 2010, 06:52:13 PM »

The MRF-150 transistor IMD 3 at 150 watts is -34 dBc and IMD 5 at 150 watts is -42 dBc. In the CW mode IMD is not a problem or there is no mixing to speak of in the CW mode. This IMD level is more than exceptible.

The MRF-150 is capable of 205 watts out for 6 watts in as long as the device dissipation is not exceeded. Some manufactures of amplifier have run the Vdd voltage higher but again device dissipation as well as VSWR limitation will come into play.
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NN4X
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« Reply #12 on: April 04, 2010, 02:09:00 AM »

Thank you for that input.

I think the point I was driving to was that, at 1,500 watts total output, each device would be contributing 187.5 watts, which is above what it's rated for.  I'll presume the manufacturer rated it at 150 watts for reasons of performance and durability.

I also noted that the IMD products seemed to deteriorate at a pretty rapid rate (Figure 4 in the datasheet).  If it were reasonable to expect that trend to continue, I'd expect that, at 187.5 watts, the IMD products would be quite a bit worse, and I'd be fearful to imagine what they'd be at 205 watts.

This is just the view of a non-EE, looking at a spec sheet.

73,
Steve
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W8JI
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« Reply #13 on: April 04, 2010, 02:46:23 AM »

Steve,

Do you think ratings are an absolute catastrophic point, and anything over that rating is instant destruction? If it were, anything run at the rating would have a short MTBF or other problems.

I also have the distinct privilege of being able to hammer amplifiers, measure gain compression and bandwidth, and get free parts when I make a mistake. I can use all the headroom and beyond and not worry. As a matter of fact there is ALWAYS latitude and it is determined by backing off from what is really unsafe a bit.

For example? I have an AL1200 that has been running with 400-600 volts more on the capacitor string than it was designed for since 1983. Never had the first problem, because those caps were purchased with 600 volt foil and 525 volt leakage tests even though the case was stamped 450V. No one tells other people to do that, but that is the actual headroom.

Here's a question for you and the data sheet....what is the saturated power of an MRF-150? It's about 600-800 watts per device at 50 volts. It's an FET, not a bipolar device. A low duty cycle medical device I built in the 80's, that has been running with virtually no FET failures, uses a pair of MRF150's at 1200 watts pulse output at 27.120 MHz.  The applicator SWR can get as high as 3:1 at that power, the only mismatch shut down is when drain voltage exceeds 150 volts.

A bipolar device won't behave that way. You can't drive the base hard enough to run much more than the rating no matter what the duty cycle. The HLA-150 amp for example saturates at about 150-160 watts with a pair of 70 watt bipolars, you can drive it with a kilowatt and it won't pulse over 160-170 watts.

FET's are neat devices, they are almost like tubes. We used very small 2N3904 sized FET's in our meter calibrators at Prime Instruments and pulsed them at 5 - 10 amps. That was about 100 times the current rating of the device we used. Duty cycle was very short, so heat wasn't an issue.

73 Tom


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K0CWO
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« Reply #14 on: April 07, 2010, 08:31:13 AM »

The power supply of my ALS-1300 blew within 15 minutes of initial operation.  I sent the RF deck and power supply back to Ameritron and had them fix the supply and perform the mods Tom suggested.  I have had it back for a couple of days now and I must say I'm impressed.  The amp is very easy to use. I can run it at 1000 watts SSB PEP all day and the thing stays cool as a cucumber.  Perfect amp to use during the summer months to help keep the shack cool!  From how it behaves for the short period of time that I have used it, I think I like it a lot!
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