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Author Topic: WARNING TO AL-82,1200,1500 OWNERS!!!  (Read 22402 times)
W1QJ
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Posts: 2845




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« on: October 06, 2013, 10:18:55 PM »

All owners of a particular run of these amps need to be aware of a potentially dangerous  shock hazard!  I have been working on these amps for over 20 years and just today I ran across an AL-82 that has a mis-wired step start relay.  This amp was never worked on.  It is NOS and it had never been plugged in.  In preparing it for it's first "turn on" since made prior to 1999 I decided to start it up without the tubes at first.  I had the cover off so that I could monitor any ill happenings.  As many of us might do, I forgot to depress the "safety switch" which is "supposed" to keep any HV from coming on if the lid is off.  WELL guess what?  When I turned the amp on I saw about 300 to 400 volts reading on the volt meter.  HUH?  With all of the other units I have worked on and made the same mistake I have never seen this condition before.  Checking the wiring of the step start relay against my Al-1500 that was just a few feet away I notices that this AL-82 I was working on had a different wiring scheme.  My AL-1500 is dead as a door nail with any HV when the cover is off with the safety switch open.  Further investigation into this matter turned up that the schematic on these amps are WRONG!  The step start/safety switch wiring does not fit the schematic and perhaps that is why the error has occurred in this run of amps.  All I can tell you is that NOT ALL units are wired wrong but some are and I urge you to check your unit to see if yours needs to be fixed.  You can get shocked if you have a unit that is wired wrong if you rely on the "so called" safety switch.  Here is what I know about this unit that is mis-wired.  This unit has a "Red Devil" type brown step start resistor which has a bracket that holds it in place with the thru screw that holds the safety switch in place.  Let that be the first indication that you may have a mis-wired unit.  There maybe others that are mis-wired with the black "Dale" type non bracketed resistor.  The second thing to look for is the wiring of the step start relay.  Looking down from the top from the front of the amp, examine your step start relay wiring.  Look to see if there is a white wire connected to the right hand side coil terminal of the relay.  There should be a white wire there that goes over to the opposite side of the safety switch and is soldered there along with a black/white wire on the same terminal.  If yours is wired like that, it is correct and no further action is required.  If, upon inspection, you do not have a white wire on that right hand coil terminal of the relay and instead you have a short wire that runs over to the adjacent relay terminal connection that has a black wire going up to the top of the step start resistor, then your unit needs to be rewired or else you have the shock hazard.  Just to prove this, try turning on your amp with the cover off and read your HV meter, you should see several hundred volts on it.  Al-1500 owners, wait 3 minutes.  BE CAREFUL though.  OK, if your unit is mis-wired here is the fix.  Where there is that short piece of wire that connects the coil relay connection over to the black wire about 1/4" away, carefully snip out that piece of wire that makes that connection bridge.  Clean the relay coil connection of old solder an wire.  Now, get a small piece of #18 or 16 wire and solder a piece on to that freed up coil connection and connect the other side over to the opposite side of the safety switch where you will find a black/white wire already attached.  Tack solder the wire there.  That completes the fix.  I am absolutely amazed that I did not catch this problem years ago but I suppose the circumstances were just right in this case in that I did have a unit that was mis-wired.  Never a dull moment when working on these Ameritron amps.  Please let us know if you have a mis wired unit so we can "maybe" come up with serial numbers that are to be looked out for.  Thanks and good luck. Lou
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N4ATS
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« Reply #1 on: October 07, 2013, 02:31:09 AM »

This thread kind of sounds familiar huh? I see misswires all the time in brand new Ameritrons , imagine that. But "they" argued with me that everything is in fact tested. Amazing find you made.
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W1QJ
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« Reply #2 on: October 07, 2013, 04:57:30 AM »

This thread kind of sounds familiar huh? I see misswires all the time in brand new Ameritrons , imagine that. But "they" argued with me that everything is in fact tested. Amazing find you made.

I posted this on the Ameritron amps yahoo group and Tom W8JI weighed in almost immediately.  This unit is NOT the only one, it is NOT an isolated case.  This is a universal mistake which appears on this particular run of amps.  My cousin has a couple of Al-1200's and I emailed him yesterday asking him to check his 2 Al-1200's.  I got a response later in the evening saying he conducted the test and his indeed is one of them.  No sure if it was both or just one.  Tom's response was interesting. I can't for the life of me figure out why they changed the wiring but they had it right in all the other amps.  BUT.... like I said, during my investigation I found that the amp WAS indeed wired according to the schematic and the schematic is wrong.  I suppose that is why the wiring on these is wrong.  If you have a close look at the the schematic of any of theses amps and you look real closely, you will see the path through the relay coil that allows  voltage to appear on the primary of the transformer hence the 300 to 400 volts of rectified DC floating around in the PS and on the plates.  Take a minute and check it out and see what I mean. Lou
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KH6AQ
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« Reply #3 on: October 07, 2013, 06:51:40 AM »

http://www.cpsc.gov/en/

US models can be reported to the Consumer Product Safety Commission



http://ec.europa.eu/consumers/safety/rapex/index_en.htm

European export models can be reported to the European Union RAPEX

« Last Edit: October 07, 2013, 07:07:08 AM by WX7G » Logged
W1QJ
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Posts: 2845




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« Reply #4 on: October 07, 2013, 07:04:42 AM »

http://www.cpsc.gov/en/

The Consumer Product Safety Commission should be informed of this safety defect.

What about letting Ameritron know about it?  I don't think the new amps coming out lately are mis-wired.  I think it was a "run " of them for whatever reason. 
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AD9DX
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« Reply #5 on: October 07, 2013, 07:14:51 AM »

I think MFJ knows.
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EX, KC9TRM, KB9IRZ
KD0REQ
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Posts: 2178




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« Reply #6 on: October 07, 2013, 10:36:06 AM »

if Tom knows, Ameritron knows.  he used to run the company, did much if not all of the HF amp engineering, and apparently continues to consult for them.  "switch to safety" is only the first step on his multi-page checklist from his writings.
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N6AJR
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« Reply #7 on: October 07, 2013, 10:54:06 AM »

And it goes with out saying, always treat the amp as if the high voltage is present, "always"  and use a grounding stick when the power is off.
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W1QJ
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« Reply #8 on: October 07, 2013, 12:13:36 PM »

if Tom knows, Ameritron knows.  he used to run the company, did much if not all of the HF amp engineering, and apparently continues to consult for them.  "switch to safety" is only the first step on his multi-page checklist from his writings.

When I reported this to the Ameritron user group last night that W8JI monitors closely, he weighed in.  From what I got from his response is that neither he nor Ameritron knew about the problem.  I think he was surprised to know this.  I explained how the problem exists and I think he looked at the schematic and saw exactly what I was talking about.  If you study the schematic of the step start/safety switch circuit closely you can see how a small amount of AC voltage appears on the primary and when rectified produces about 400vdc in the power supply and is present at the tubes as well.  One would suspect that a high voltage interlock would be doing it's job but someone goofed up someplace and the wiring of this circuit was changed.  Obviously somebody did not anticipate the small voltage that passes through the relay coil.  The amps that function properly actually ARE NOT wired according to the schematic.  The schematic is wrong.
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KH6AQ
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Posts: 7718




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« Reply #9 on: October 07, 2013, 12:21:23 PM »

W1QJ, looking at the AL-82B schematic the relay RLY3 coil is across of the HV transformer primary windings but without HV interlock S5 closed there is no path that applies AC power across one or the other transformer primary winding.

http://www.ameritron.com/pdffiles/AL-82.pdf

« Last Edit: October 07, 2013, 12:23:46 PM by WX7G » Logged
9A4WY
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Posts: 30




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« Reply #10 on: October 07, 2013, 12:57:21 PM »

Lou...
I just went through this problem before few months on my amp...(I replace ANT. relay with GH1+RSD12 relay)
plate caps was not SC to GND and I saw few hundred volts on meter.
then it powered off and HV bleeds down to 0......AMP ON...HV climbing up again...what is it !!  
I was thinking I am crazy!!!
I left it powered on and after about a minute coil opened up...then I knew what is going on.
I thoroughly check wiring and found a problem, and then, amp was rewired.
mistake was that I did not post my findings here
Kristian,9A4WY

S/N 1240
« Last Edit: October 07, 2013, 01:00:57 PM by 9A4WY » Logged
W5JON
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Posts: 354




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« Reply #11 on: October 07, 2013, 02:07:21 PM »


When I reported this to the Ameritron user group last night that W8JI monitors closely, he weighed in.  From what I got from his response is that neither he nor Ameritron knew about the problem.  I think he was surprised to know this.  I explained how the problem exists and I think he looked at the schematic and saw exactly what I was talking about.  If you study the schematic of the step start/safety switch circuit closely you can see how a small amount of AC voltage appears on the primary and when rectified produces about 400vdc in the power supply and is present at the tubes as well.  One would suspect that a high voltage interlock would be doing it's job but someone goofed up someplace and the wiring of this circuit was changed.  Obviously somebody did not anticipate the small voltage that passes through the relay coil.  The amps that function properly actually ARE NOT wired according to the schematic.  The schematic is wrong.


Are they saying that none of the service technicians at either MFJ or Ameritron have ever seen this on any of these Amplifiers that have ever been sent in for repair, and I am sure there have been many?  

However now that they do know, it will be interesting to see what they do to let the owners of these Amplifiers know of this potential lethal problem.

73,

John
« Last Edit: October 07, 2013, 02:09:45 PM by W5JON » Logged
N4ATS
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Posts: 1253




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« Reply #12 on: October 07, 2013, 04:03:17 PM »

For a company that stated in previous threads that EHAM feedback on their products are useless and most hams are incompetent, I would think you will hear nothing.
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W1QJ
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Posts: 2845




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« Reply #13 on: October 07, 2013, 04:04:25 PM »

W1QJ, looking at the AL-82B schematic the relay RLY3 coil is across of the HV transformer primary windings but without HV interlock S5 closed there is no path that applies AC power across one or the other transformer primary winding.

http://www.ameritron.com/pdffiles/AL-82.pdf


There is a path from one side of the 240v line to the center tap.  The path through the coil which is NOT isolated by the safety switch causes a small voltage to the primary and hence it gets rectified and presents about 400 volts of HV in the power supply and on the tubes.  The fix is to isolate the primary coil of the step start relay by moving the one side of the coil to the other side of the safety switch thus breaking the series circuit.  Check again. Lou
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W1QJ
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Posts: 2845




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« Reply #14 on: October 07, 2013, 04:06:02 PM »

For a company that stated in previous threads that EHAM feedback on their products are useless and most hams are incompetent, I would think you will hear nothing.
Bill, looking at the schematic posted by Wx7 do you see the path that causes the primary to get somce small voltage that can be rectified?  Lou
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