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Author Topic: Bought a brand new Ameritron AL80B 1KW amplifier...  (Read 8611 times)
W7HBP
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Posts: 166




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« on: April 07, 2013, 05:45:49 PM »

...Just petrified to fire it up.

OK, have it set up with "radio/Icom IC-746---amplifier-----LDG 1000W tuner----Diawa Power/SWR meter----antenna switch-----antenna"

I powered it up, on standby only. Meter set to HV, went up to around 28, which appears to be good (2800 volts).
 
I have been going over the book, still unsure on procedure. ALC? Do I need another input to the amp from the radio? It appears I can or not? It reads both. Do I need an ALC wire? This is my first amplifier and its brand new, never TX'd with it yet. Just wired up its own designated 20A 125VAC circuit. I purchased the MFJ tuner stick to tune the slugs (input) its been modified for 10, 12 meter. DX engineering sent me that info. I'm ready to go, but nervous as a long tailed cat in a room full of rocking chairs.

There is an ALC circuit in the back too. I know once I get it up and running, running threough the steps, it will be a snap. But I just dont want to start out with a wrong step in the beginning.

I've owned it for over a month now and haven't used it yet. I will continue to re read the manual over and over. But if a veteran who uses this exact amp has any advise, be greatly appreciated. Thanks.

Rick
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N6PJB
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« Reply #1 on: April 07, 2013, 07:11:42 PM »

I have never used the ALC with my 746 Pro and my Al-80B. I have the RF Power on the 746 set to 100 watts or less. Give it a try into a dummy load.

Philip
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W9KDX
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« Reply #2 on: April 07, 2013, 07:13:43 PM »

You will get more expert input, but I can address the ALC as my 811H has similar.  ALC is a back up system to help keep the amp from frying if you input too many watts from your Icom.  It is not a fail safe system but it will limit your input.  After you have determined the correct watts in for the different bands, you will adjust it.  I have not read anyone here who says you should not use it, and of course if you never, ever make an error, you won't need it.  I always use it as I am human and I don't ever want to shove 200 watts in because I got excited about Antarctica.

I was just as cautious as you.  After a few weeks and some input from here and the purchase of a pulse exciter, I can now tune up in just a few seconds and I feel much less convinced that I am going to blow something up.

I am not sure about the Icom, but I would guess that you do need a separate connector.  My Yaesu and 811H use a simple RCA connector and I know that at least the 80B does the same.
« Last Edit: April 07, 2013, 07:21:22 PM by W9KDX » Logged

Sam
W9KDX
KA9CCH
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Posts: 87




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« Reply #3 on: April 07, 2013, 08:23:59 PM »

Try your tune and operating procedures off the air into your dummy load.  You can then gain confidence in the operation of the amp.


KA9CCH
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K8AXW
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« Reply #4 on: April 07, 2013, 08:43:13 PM »

Rick:  I feel your stress level man.  After running my homebrew amp for 30 years and my SB-200 for about 5 or 6, I still maintain a pucker factor of about 9 whenever I mess with them!

But, the main thing to do now is gain some confidence in using this fine piece of gear.  Follow Ameritron's instructions for loading it..... even making a "cheat sheet" if you need to.

Inject a little signal into the amp (CW mode) and watch the meters.  Dip the plate current or tune for maximum power output as they suggest.  Just keep adding a little more to it and before you know it, you'll be at full output!

Then: You keep a record of the control settings and refer to them each time you change bands or make radical frequency changes.

One thing to remember is that you always tune the amp for full output.  Nothing less.  Then if you wish to run at a lower output level just back off on the drive until you get the output you want.

You don't HAVE to have the ALC connected but you will need to watch your drive and amplifier meters to make sure you don't overload or over drive it.  I don't run ALC on either of my amps.  Just watch it!
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NO2A
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« Reply #5 on: April 07, 2013, 09:13:02 PM »

Being a new amp the idling hv should be more than 2800 volts,however,that could be the metering resistors giving a lower reading. Running it off a dedicated 20 amp line is very good. I would tune it and find out what your power output is. Ideally the hv under load should be around 2700,and at idle at least 3000-3100. If of course you are getting the rated output on cw then it is ok.
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W8JX
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« Reply #6 on: April 07, 2013, 09:22:07 PM »

I never use ALC. I run the same power output from rig, 50 watts, barefoot or driving amp so never worry about over-driving it.  BTW I am very comfortable using or tuning a amp. Just do not worry about trying to squeeze out that last 100 watts or so as it will make no difference down range and the 80b will last longer too. I have used a old Dentron amp with 4 ea 572 for nearly 20 years now running 800 to 1100 watts (based on 1900 or 2700 volt plate volt switch setting) on a 15 amp 240 volt circuit. Do the match if you need more than 15 amps you are doing a lot more than 1500 watts too. 
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K4RVN
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« Reply #7 on: April 07, 2013, 09:41:18 PM »

Rick,
you will need to connect a cable from the back of your 746 transceiver send  to the amp relay. Also later if you want to use the ALC another cable from the 746 to the ALC on the AL 80 B. These probably have RCA connectors on each end for the 746 and the AL80b for sure.
Here is what I would suggest to expand on previous posts. Turn to page 79 in your manual and follow the diagram for connecting a non Icom Linear. You don't have to use the ALC running the drive power I have suggested for learning to tune up. You can leave the ALC cable off at this time.

Go in your AL 80 B manual and select the band you want to use and note the pre-sets for that band to use on plate and load.  Set the band switch and presets on your amp for that band.
Write them down for handy reference.
Set your transceiver on that same band and turn the drive power down to 20 watts on the 746.

Use the 746 tune switch if it has one or CW mode and key the amp using only 20 watts to drive the AL80B.
Turn the plate control for max power out on a watt meter.
Then turn the load control for max out on the watt meter. Touch up the plate again for max out. You should see over a hundred watts out if your amp is tuned properly with 20 watts drive. The 20 watts will not hurt your amp and will let you learn to tune the amp. Tune quickly as possible.
If all is well turn the 746 drive up to 40 watts and retune using the aforementioned procedures. You should see 200 watts or more out this time if all is well. You can switch to SSB and call CQ if you like now using the 40 watt drive power.
All meter readings should be well below max if you are tuned right. the grid and plate both will be way below max at this point so don't worry about them at this procedure if all looks OK.
By all means do not even think about using the tuning wand on the tuned input until you learn to use the amp with your setup and antenna.
After you learn to tune and use the amp at reduced power, then go up to about 75 watts drive and get about 900 watts out on the watt meter. I would not advise you to try for 1KW until you learn more .

Good luck Rick and go for it. I have used this tuning procedure on my older AL80A for over 20 years without hurting it so good luck if you decide to use your amp. Let us know how you made out please.

Frank
« Last Edit: April 07, 2013, 09:58:40 PM by K4RVN » Logged
NO2A
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Posts: 801




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« Reply #8 on: April 07, 2013, 10:22:21 PM »

Frank brings up a good point I think more new amp owners should pay attention to. Never adjust the tuning input slugs unless there is an actual problem with them. This is like messing with your car`s alignment when nothing is wrong. The slugs are preset from the factory to cover the bands in use. Even on bands like 10/12,15/17,it isn`t necessary. They are set to cover both bands,and they do. So unless your input swr is way off,please don`t.
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K2DC
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« Reply #9 on: April 08, 2013, 03:00:51 AM »

Rick,

   You need to move the power/swr meter.  It should go between the amplifier and the antenna tuner.  The way you have it configured now, the meter will not show the impact of the antenna tuner.  The lineup should be:
rig-->amp-->meter-->tuner-->switch-->antenna.

73,

Don, K2DC
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VE3FMC
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« Reply #10 on: April 08, 2013, 05:17:08 AM »

Hi Rick

First congrats on buying a fine amp. I have the older brother, the AL-80A.

I do not have the ALC line connected. I do not drive the amp with more than 70 watts, and the maximum I can drive it with is 100 watts. So I just didn't bother with the ALC connection.

One hint I will give you and this makes future operation of your amp much easier.

Load the amp into a dummy load on every band. Once you get it loaded on a band write down the plate and load settings. Do this on every band you plan on running the amp on.

Now you have a loading chart which allows you to set the plate and load settings before keying the amp. Then you just have to do a quick touch up on the plate and load settings and you are good to go. This saves a lot of key down time on the amp when changing bands.

I start off with about 40 watts drive on FM on my FT-950, then increase the output on the radio to tweak the plate and load settings on the amp. Once it is loaded up I then back the rig power off so I get the power out of the amp that I want to run.

The reason I use FM is because I do not have any CW key or paddle connected to the rig.

Have fun, use the amp wisely and you will get many years of use from that 3-500Z tube.
Rick VE3FMC
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W7HBP
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Posts: 166




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« Reply #11 on: April 08, 2013, 11:33:16 AM »

Thanks to everyone who replied. All great advice, ie start with low input, move watt meter before the tuner etc. It was a very expensive piece of gear and I didnt want to make really expensive smoke.  Grin Even if Ameritron  warrantied it, shipping it along is a small fortune, plus sending the tube seperately is another expense.

I did not tune the input slugs. I did purchaser the special plastic tool from MFJ anyway. But I will not mess with anything as of yet. I have been re reading the booklet, each time, it makes more sense.

I appreciate al the very nice and polite replies. I wasnt sure if I was going to get a bunch of "smart alec" responses. I didnt get a one. Thanks for undestanding my concerns and walking me through this. This weekend or sooner may be the real test.

I feel much more confident now, but still a little nervous. One trip through with no expensive smoke, melting down or arcing, I'll have it down.  Wink

Thanks again to everyone for the very nice replies.  Cheesy

73 from W7HBP
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W8JX
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« Reply #12 on: April 08, 2013, 02:01:50 PM »

The reason I use FM is because I do not have any CW key or paddle connected to the rig.

You can use FSK mode (if you have it) and hit send too.
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NT6U
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Posts: 68




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« Reply #13 on: April 08, 2013, 05:13:09 PM »

I do not use the ALC, works great for me.  I never run more than 75 watts into the amp.  Good advise from another don't try to squeeze everything out of it.  I run older kenwood radios with the AL 80 B.  Do you have a Ham Radio club in your area, get with someone with expeirence, I'm certain an elmer would help.  One thing also... don't worry and have fun, the 3-500 tube is forgiving.
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N6AJR
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« Reply #14 on: April 08, 2013, 07:49:28 PM »

I never use ALC and have had many amps. find a local ham familar with amps and have them come and help you out.   its easy once you see it done a couple of times
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