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Author Topic: Ameritron 811H  (Read 4918 times)
KD8GKR
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Posts: 47




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« Reply #15 on: March 15, 2011, 09:50:26 AM »

Strange this problem occur after changing the metering diode (D16). I believe it is a 1N4007 diode. Check the 51 ohm resistors, which W8JI discusses removing. The link has been posted twice. They are located under the tube sockets. Check the band switch wafer, look for burns and make sure it make contact in all band positions(wafer should be blue). Back to the Diode check that you installed it the correct direction. Now is also a good time to remind you of high voltage, be careful when working inside an amplifier.
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KM5PS
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Posts: 82


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« Reply #16 on: March 15, 2011, 10:54:25 AM »

I have emailed W8JI about my problem, I don't know if he answers emails or not thought I would try.  I am planning on cleaning the plate air capacitor tonite with alcohol and a brush when I get off work.  That is mentioned in the manual for routine maintance.   The swr on my hygain th5 tribander for 20 meters is 1.6:1.  That is also what it is on 15 meters and 15 meters is working fine right now...

Thanks again for the help

John
Km5ps
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KM5PS
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« Reply #17 on: March 15, 2011, 08:17:16 PM »

I think now I may have a bad Plate tuning capacitor.  I did talk to Ameritron today.  They told me a few things to check.  Tonight I checked to see if I had a bad tube, but all seem okay, or at least pasted the test Ameritron told me.  But on my Plate tuning capacitor I noticed on the 2nd or 3rd fin from the back of the tuning capacitor that you can see where it has been arcing.  So may have to replace the Plate tuning capacitor.  Will keep progress going so if someone else is having similar problems it might help them out.

73's
john
km5ps
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W8JX
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Posts: 5657




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« Reply #18 on: March 15, 2011, 08:42:40 PM »

My concern is what caused arc to begin with. I do not think it was cause of arc but rather the result of another problem.
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W1QJ
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Posts: 1444




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« Reply #19 on: March 16, 2011, 05:27:46 AM »

John, are the plates removable on that cap?  If so I can repair the cap for you.  Lou
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W8JX
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Posts: 5657




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« Reply #20 on: March 16, 2011, 11:50:19 AM »

Most likely not. In old days parts were "built" but now they slap the stamp them together.
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KM5PS
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« Reply #21 on: March 16, 2011, 07:05:32 PM »

I talked to Ron (a technician) again today at Ameritron.  To find out what the part number was for the Plate tuning capacitor.  He told me Monday that was the Plate was damaged, you can not fix them.  But he does work for Ameritron.  He told me that they are too hard to change out.  He said he does not take anything loose or out, to get the part out.  So I am planning on ordering a new Plate tuning capacitor and maybe a new PCB Parasitic Board.  Does anyone know what MFJ's part number is for that board.  I called them today and got a message machine and left a message, but know one called me back.  They are a little cheaper thru MFJ rather than Ameritron, or at least the Plate Capacitor is.  Ron did tell me Monday, that it sounded like I had several problem going on.  But he did not elaborate what they might be.  I did change the PCB board out to the one that I had tried that was blowing the fuses, but now it does not, and checked the tubes like he said, and all okay.  No blown fuses so far.  I have also tried to clean the RF Relay tonight.  Hard to clean.  Here is a link for pics I took of the Plate tuning Capacitor-if you look at back 4th fine you can see the tip is messed up some.  Picture # 9&10.   http://km5ps.com/AL811H

John
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W8JX
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« Reply #22 on: March 16, 2011, 07:29:06 PM »

From what I see in pics I would just dress it up with a jewelers file and be done with it. Damage is not that bad.
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KM5PS
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« Reply #23 on: March 17, 2011, 09:35:19 AM »

Update here.  I took a piece of emery cloth on the end of a Popsicle stick and touch up the bad spot on the Plate Capacitor and tuned up on 20 meters just fine.  No arcing as of now.  Will try it some today on 20 meters. 
Thanks everyone!!

John
km5ps
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KM5PS
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« Reply #24 on: March 17, 2011, 01:24:36 PM »

Good news- amp is back to tuning properly on 20m. I have been on the air with this afternoon putting out about 700 watts on cw, and no arcing.  So I hope the problem is fixed for now.  I may have been tuning the amp wrong.  From what I have been reading on W8JI site, I may have been causing the amp to start arcing.  I usually started out at about 20 watts  for tuning then moved up in 10-15 watts increments.  I watched the tuning video off of Youtube about tuning amps, and started tuning a little differently than what I was doing.  So for right now everything is working A OK!!  Again thanks to everyone who responded and tried to help.  At least I got to learn a little on how to work on my amp. 

John
KM5PS
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