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Author Topic: Got replaced 811H From HRO  (Read 3620 times)
NH7FL
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Posts: 23




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« on: July 22, 2012, 03:07:44 PM »

A follow up to the old amp postings I left a few days ago. So here is the story on the new amp (exchanged).  The old tuning problems are gone, and at 20 meters the power supply no longer shuts off.  The amp will easily tune and I can drive it up to 300 watts easily with just a little bit of power, about 20-25W will produce 300 out... however it won't do any more then that..except on 80 it will top out at around 500.  Am I doing something wrong here?  Very frustrated. The amp hits a wall... plate current maxes out 450ma and no more.. grid current shoots up as I excite with a bit more power but no more out.   

Link to old thread.

http://www.eham.net/ehamforum/smf/index.php/topic,84196.0.html
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KA5N
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Posts: 4380




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« Reply #1 on: July 22, 2012, 03:19:45 PM »

Perhaps the exciter's ALC  is cutting the drive back.  Have you checked the input SWR?
Maybe the input coils are mistuned, maybe 80 meter input ckt is OK.  Are you sure all your
hook-up jumpers are good?  A coax jumper with a missing shield connection or short or
intermitten connection can play havoc with operation.  Did you check your tuner for
arcing (as was suggested in a former post).  How is your SWR going into your antenna?
Eventually you should be able to get everything working at the same time, you may have
grey hair, but heck that comes along anyway.
Good Luck
Allen Ka5n.
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N4CR
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Posts: 1668




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« Reply #2 on: July 22, 2012, 03:21:14 PM »

Do you have the ALC line hooked up to the rig?
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
NH7FL
Member

Posts: 23




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« Reply #3 on: July 22, 2012, 03:23:16 PM »

I don't have the ALC hooked up.. only the relay.
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N9DSJ
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Posts: 23




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« Reply #4 on: July 22, 2012, 03:25:18 PM »

How are you measuring your output power?

73,

Bill N9DSJ
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NH7FL
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Posts: 23




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« Reply #5 on: July 22, 2012, 03:41:05 PM »

How are you measuring your output power?

73,

Bill N9DSJ

I'm using the meter on the tuner, however I don't think it would be off by 300-400 watts, however I'll take any advice here.
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N4CR
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Posts: 1668




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« Reply #6 on: July 22, 2012, 04:26:14 PM »

Next thing I'd want to know is how it works into a dummy load.
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
N9AOP
Member

Posts: 145




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« Reply #7 on: July 22, 2012, 04:34:07 PM »

Hi,
I don't see anywhere in your posts that you are using a dummy load and you really ought to because then you know for sure that you are running into a 50ohm load.  Also, you won't be splattering all over the air when tuning up and it takes any antenna problems you may have out of the problem solving equation.  As far as ALC goes, I don't use it because TenTec equipment doesn't use it and I have no problems with the amp.  I have run the 811A for several years with no problems and once you get things sorted out you will find it a reliable unit.  Remember also that when MFJ says that it will output 800 watts, that is near the incinerate level.  If you run it at 500-600 watts, the tubes will last many years.  One final thing you could do is take the amp over to a friends house and try it with their exciter and see what happens.
Art
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K0ZN
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Posts: 1548




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« Reply #8 on: July 22, 2012, 05:05:26 PM »

I don't mean to sound condescending.... just trying to get more info. It is pretty hard to troubleshoot without being at the equipment in question!  

You are driving it with a continuous carrier, such as key down CW or RTTY mode from the exciter, correct?

What is the SWR that your exciter "sees" when driving the amp?  It should be very low on the "major" bands....80, 40, 20, etc.

You are sure about the power output of the exciter being adequate?

What is the GRID current reading at 300 W output ? What is the PLATE voltage, key down at 300 W output?

Pick ONE band, say 20 M:  What are the plate and Load control settings at maximum Output?  Are they near what the Owner's Manual specifies?

Agree with other posts that a dummy load would be very helpful in this situation.

Are all four of the tube filaments on and glowing?  (20 to 25 IN and 300 OUT sounds about right for 3 tubes.....)

Are you running on 120 or 240 V AC line?   Is the AC line capacity adequate for the load?

Tube quality/reliability issues, unfortunately, are very common with the current Chinese 811A tubes. (You can see that from reading
other postings here on Eham. I went through 6 tubes to finally find 3 good ones in my AL-811.)

Thing seem to be somewhat better lately, but in the past Ameritron/MFJ products have been pretty notorious for inadequately tightened nuts and bolts/fasteners ,etc.
(I have an AL-811, which had SEVERAL very loose/untightened nuts, one of which was a critical grounding lug. ) I would strongly
recommend you go in and carefully visually inspect > EVERYTHING < in the amp. Check ALL the nuts and screws for tightness.
Look over solder joints on the power supply board, and/or the physical integrity/tightness of other wiring connections, etc.

IF you go inside that amp, MAKE SURE it is SAFE and everything is discharged !!  There are LETHAL voltages inside that box !

If all else fails:  Call Ameritron and talk to one of their tech people.  Nobody knows more about those amps than they do !


73,   K0zn

« Last Edit: July 22, 2012, 05:09:05 PM by K0ZN » Logged
W1QJ
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Posts: 1447




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« Reply #9 on: July 23, 2012, 06:00:14 AM »

This is amp #2 that you got now that you think is not working just right.  I'm not sure if this is a pattern or what.  Now that you are an amp owner you have sort of an obligation to own some complimentary equipment.  YOU NEED... A dummy load, and a good external watt meter.  I don't trust meters in tuners.  A simple used Heath Cantenna or an Ameritron 1 gallon paint can job is fine.  As far as a decent watt meter that won't drain your pocektbook, buy a used Diamond SX100.  You DON'T need a Bird 2500 watt dummy load like I have or a Post LP-100A wattmeter like I have.  The Cantenna or Ameritron unit and a SX-100 is fine.  Unless you load up into a dummy load and read power with a decent meter it's anyone's guess just what's going on there.  It is entrerly possible that you are not properly loading up the amp.  Unfortunately the tubes in that amp can easily be damaged if you do not load the amp up properly.  An AL-811H should easily load up to 600 watts or more of key down carrier.  SSB power should reach 800 PEP easily.  Can you tell us step by step how you approach loading up this amp?
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WX7G
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Posts: 6076




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« Reply #10 on: July 23, 2012, 06:07:31 AM »

With two amps both showing the same low power the spotlight is on the wattmeter in the tuner. How to tell? Run the transceiver only into the tuner/antenna at maximum transceiver power. If the transceiver is rated for 100 watts and it indicates, for example, 50 watts you know the wattmeter is the problem. Use the same tuner power range as you do with the amp.
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NH7FL
Member

Posts: 23




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« Reply #11 on: July 23, 2012, 06:51:19 PM »

Again, appreciate all the help and comments.  So here is the final verdict.  Got another ham to help me out... hooked it up to a 2KW dummy load and a quality wattmeter.  Essentially the results were the same.... Even used 2 different radios to excite.  Called ameritron with all the pertinent data and was told I most likely have some bad tubes.  Tested my tuner and antenna on a solid state amp and got full power output with that validating that my tuner meter was very close to the actual output though off a bit in the other direction so even less power out.  I also replaced the feed line with some beefy coax while I was at it. I'm not sure whether to send the amp to ameritron or return it, just spend the extra money and get a different brand/model.  Hopefully I'll have better luck in the future, for now 100W will have to do.  I've learned a whole lot, and again, appreciate all the help I've received. 

-Art
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N4CR
Member

Posts: 1668




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« Reply #12 on: July 23, 2012, 07:13:26 PM »

So do you have the same tubes in this amp that you had in your previous one? They swapped the amp and you kept the same tubes?
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73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
WX7G
Member

Posts: 6076




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« Reply #13 on: July 24, 2012, 01:25:38 PM »

I had an AL-811 amp and had tube problems. So I upgraded to an AL-600 and it has been trouble free running 600 watts on CW.
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