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Author Topic: Ameritron AL-82 Relay Problem  (Read 6861 times)
K0BX
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Posts: 40




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« on: November 15, 2004, 08:20:35 AM »

Our club station has a AL-82 amp (2 3-500Z tubes) and it works very well.  We only have had it for about a year and it is hooked up to a IC-756 and using a Ameritron RB-706(cant remember the number) but it the relay interface.

The problem is that sometime when we go from xmit to receive the relay stays closed and the recieve signal go's way down.  A quick hit of the PTT and the relay un-sticks.

Has anyone had this problem or know how to fix it?  Really don't want to ship it back.

Joe K0BX
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WB2WIK
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Posts: 21837




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« Reply #1 on: November 15, 2004, 08:41:49 AM »

You sure it's not the interface box that has the problem?

It's unusual for a relay to stick "closed."  Poor or intermittant contacts are a common problem, but that wouldn't caus the relay to actually stick in the transmit position.

Of course, if you've misdiagnosed this and the relay really isn't "sticking," but simply isn't making good connection to the "RX" side when it opens, that would be a different problem: Could be some dirt on the relay's RX contacts, and it doesn't take much to make a poor connection.  If you want to clean the relay contacts, of course first be very careful when you remove the amplifier's cover (and be sure it's unplugged first!), find the relay, and wipe a dollar bill or similar paper through the contacts to clean them.

NEVER use sandpaper, emory cloth or any sort of file on relay contacts!  A piece of paper (I use a dollar bill, because it's just about right for the job) works pretty well.

WB2WIK/6
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NI0C
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Posts: 3270




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« Reply #2 on: November 15, 2004, 03:04:15 PM »

Joe, I had this problem with my AL-80B.  Turns out the relay contacts (in the amplifier) needed cleaning as Steve suggested.  Go to Gateway Electronics and get a small can of contact cleaner and a package of chamois sticks to apply it with.  The contact cleaner and chamois sticks are on the same wall-- as I recall these were at the South end of the store. This worked for me.  I tried the dollar bill approach but could not get it on the receive contacts of the relay.  The chamois sticks (which are like a flat Q-tip) made the job very easy.  

73 & GL,

Chuck  NI0C
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K0BX
Member

Posts: 40




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« Reply #3 on: November 16, 2004, 06:45:51 AM »

Thanks for the suggestions.  We have another MFJ amp interface in the shack for our IC-775DSP and Henry 4K so I will take it out of line and put it on the station that has the problem.  If that is not the problem We will clean the contacts on the relay as suggested.  It just doesnt seem like the relay should be dirty after only a year?  I have never clean the relay in my Drake L-7 (20 years old) or the Henry 4K which was used a a lab every day for 20 years.

But thanks for the suggestions.  We have another AL-82 that is brand new but because of poor QC from MFJ we are waiting parts before we can put in line.

Joe K0BX
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W7DJM
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Posts: 1




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« Reply #4 on: November 16, 2004, 08:14:18 AM »

The very FIRST THING to do is find out where the problem lies.

Is the exciter somehow "leaking" enough voltage/contact closure in the exciter internal circuitry that it is hanging up the interface?

Does the interface hang up, from problems within?

Does the amplifier hang?

One thing you can do, is "get it to hang,"  and then pull out the relay cable.   To test the amplifier, you need to pull the cable loose in a manner that is PHYSICALLY APART from the amp, because just the act of pulling the cable out the jack on the amplifier may jiggle things enough to hide the problem.  Ya just might need some extra leads and test clips.

On a used AL80B I recently bought, the pigtails for the T/R relay that go from the circuit board on which it mounts to the relay armature had some solder wicking in them which reduced their flexibility, causing intermittent contact failure GOING BACK INTO RECEIVE MODE.

Carefully removing and replacing these solved this problem.
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WA1RNE
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Posts: 1010




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« Reply #5 on: November 16, 2004, 05:04:05 PM »


 First of all, you don't need to use the ARB-704 Interface Buffer with the IC-756.

 Since the 756 will switch up to 2 amperes on a 16 vdc line, you can wire it directly to the AL-82.

 The AL-82 runs ~12vdc through its change-over relay coil during standby; To transmit, this line (RELAY) gets pulled to ground by the 756. Since there is no high voltage bias being switched on the relay circuit, the 756 only has to deal with 12 vdc at 100 milliamps - way within the ratings of the 756's built in relay.

 Not knowing the jumper settings you have selected within the Interface Box, my guess is that they are wrong and causing the relay to hang when you release the PTT switch. Probably set up originally to switch the Henry amp??

 Good news, a simple fix.....
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WILLY
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Posts: 286




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« Reply #6 on: November 18, 2004, 09:46:53 AM »

RE: Ameritron AL-82 Relay Problem      
by WB2WIK on November 15, 2004

"...
NEVER use sandpaper, emory cloth or any sort of file on relay contacts! A piece of paper (I use a dollar bill, because it's just about right for the job) works pretty well.

WB2WIK/6 "

Related questions:

What about crocus cloth for this job?   Still too coarse?

And, is crocus cloth the finest, or is there some other that is even less coarse?
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W7DJM
Member

Posts: 1




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« Reply #7 on: November 18, 2004, 10:42:10 AM »

Just about anything that is sold as "abrasive"  is much too much so for relay contacts.

In the navy, we used to have "relay burnishing tools" that came in a pen-like case.  The "blades"  for burnishing had no detectable abrasive, they looked sort of like an oxidized piece of aluminum--just dull grey color, and very flexible.

The problem with ANY abrasive is that it can leave deposits of the abrasive itself imbedded in the contacts, which will itself pit and prevent contact.
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