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Author Topic: AL 811 Amp help  (Read 1165 times)
F5VDM
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Posts: 11




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« on: May 29, 2011, 11:52:01 PM »

HI

I bought a used 811 which seems in reasonable condition.  It works just fine on 17meters putting out around 500 watts.  I am unable to get the thing to work at all on any of the other bands, it will tune up on 15 to about 200w but when I move the LOAD and PLATE capacitors on the other bands (20m for example), nothing happens.  I am on the correct band switch.  Its like there is no capacitive effect at all.

Any ideas?

thanks.

Garry
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KA5N
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Posts: 4380




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« Reply #1 on: May 30, 2011, 02:18:42 AM »

Most likely there is something amiss with the bandswitch.  You are going to have to open the amp in order to check things out.  If you are not knowledgeable to do this safely then you are going to have to seek help or find a repair person.  Of course you must unplug the amp and discharge the capacitor bank (or at least leave the amp unpowered for several days). There are lethal voltages present in the amp.
Often bandswitches have shafts that are in two (or more) sections with a coupler inserted so that the halves turn together.  Here the problem is often just a loose or missing set screw so that one section of wafers is switched while the other section stays in the same position (this could very easily be your problem).  
Other times the wafer switch contacts can be bent or even burnt off!!!  Since the amp works correctly on 17 meters and sort of OK on 15 there is probably nothing wrong with the tuning capacitors.  So likely the shaft is loose or the input switch wafer is shot.
Allen
« Last Edit: May 30, 2011, 07:37:08 AM by KA5N » Logged
VR2AX
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Posts: 577




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« Reply #2 on: May 30, 2011, 06:06:11 AM »

Can you get 'normal' output on 15 by retuning the input? At the expense no doubt of the output you're presently getting on 17m? If so that would tend to suggest the band switch is 'stuck' (electrically) in the 15/17m position.

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WD8T
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Posts: 126




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« Reply #3 on: May 30, 2011, 04:35:49 PM »

Download the manual and post your results once you try to tune it per that document.
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KD8GEH
Member

Posts: 464




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« Reply #4 on: May 30, 2011, 07:54:01 PM »

Let her sit over night and pop the lip off. Like the other gent said, I'll bet you have a missing screw and/or damaged band wafer switch. Good news is they are not too bad cost wise and pretty easy to replace if its beyond repair.

Be carefull. If I can be of any further help, feel free to contact me via qrz. I have an H model. I have done about every mule headed mistake and managed to repair it with a little help from my friends.  Grin

Cheers from Dave
KD8GEH Near Dayton
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F5VDM
Member

Posts: 11




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« Reply #5 on: May 31, 2011, 11:19:58 PM »

Thanks to all who responded.  The problem is fixed. In fact it was 2 things.  I had a look at the switch yesterday and found that ti was not quite touching the 20m connector, pushing it down with a small screwdriver helped.

Also the connector wire to the coil had actually desoldered.  Fixed and now all works.

regards

Garry
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KD8GEH
Member

Posts: 464




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« Reply #6 on: June 02, 2011, 02:51:35 PM »

Congrts Garry!

Welcome to the "Beat to fit, paint to match" Club

Hope to year you down the log.

De Dave KD8GEH
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