Sorry forgot to add the link:  http://km5ps.com/AL811H  and look at the 10 mtr mod picture..
John

Gary- Did you get your AL811h working on 10 mtrs?  I am trying to get mine also to work for 10 mtrs. I cut the wire that was mentioned and still not working here.  I may need to tune the coil first before it will work.  I have to borrow the right size of hex wrench from a friend first.  For anyone who can help I have a link below showing the wire that I cut.  Is this the right wire?   I am getting 460mA on plate current and abt 60 mA on Grid current with 30 watts of drive.  When I tune the amp there is no change in readings.  Any help would be great..

John
km5ps

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

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

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

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

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

Does anyone know how to neutralize an AL811h amp? I have read through the manual and can not see it anywhere.  Unless I have over looked it.  I have found where they talk about cleaning the air variable capacitors, but that is it.  Any help would be great..

John
km5ps

W8JX-  How do you neutralize the al811h amp.  From what I have read about them you should not have too..  This is my first amp so I am new to all of this.

john

Did some more testing since last post and seems to only be arcing on 20 mtrs.  Tuned up on 15,40,80 mtrs and was okay.  Might be a bad spot on plate capacitor for the 20 mtrs.  Just guessing here. 

John
km5ps

New problem with 811h amp. Replaced the D16 diode tonight, and now when I tune up the amp, the amp is arcing on the Plate Tuning Capacitor.  The amp is also showing 500 watts out with only 25 watts of drive.  When it amp arc the power cuts out.  Anybody have any suggestions what might be wrong?  I have emailed W8JI to see if he could help me.  Odd that just replacing the D16 diode the amp is acting like this.  Any help wud be great. 

Thanks
John
km5ps

Can anyone tell me what to look for to know if my al811h has the 10 meter mod done or not? 

John
km5ps

K2OWK
The reason why I was trying replace the board was because of the bad burn around on the bottom of the board.  I was afraid that it might start arcing again.  It was also suggested to me by a couple of local hams who helped me, learning how to use the amp.  But of coarse after I had put the new board on and it started blowing fuses, I wished I had not done that of coarse.  It was also a learning experience for me also.  Now I get to replace Diode D16 which is bad, since it protected the meters.  Anyway thanks for the relpy..

73
km5ps

The metal ring is on the wire from the choke to the bottom of the board.  I was afraid after looking at the wire, that it might be touching one of the capacitors or resistors solder pads on the bottom side of the board.  Is the lock washer suppose to be mounted on top of the board or underneath?  Mine when I first took off the board the first time was on top underneath the screw head.  That is where it is now and the washer I put in is underneath the board and on top of the metal connector ring on the wire coming off of the choke.  The Grid Current meter seems to be reading higher than it did before.  Now it reads maxed out more easily when tuning than what it did before.  That is the only difference that I have seen so far.  I am also running about 55-60 watts into amp and getting 600 watts out on cw on 20 meters.  Only band I have used since worked on amp.  The link below shows the arcing on the new board when fuses were being blown.  The old board is a lot worse off.  Half of the pad on the bottom is gone.  Did not want to take old board back out yet, since amp is back to working.  http://km5ps.com/AL811H   for pictures.

John
KM5PS

I have just recently bought a AL811H at a local hamfest.  This is my first amp.  When I first started using it I noticed that the amp was arcing  underneath the pcb board on top of the tubes.  I took it over to a local ham for him to look at.  We took the pcb off and the underside of the board was burned pretty bad.  We cleaned up the arcing traces and replaced the board with a washer on the underside of the board since half of the solder pad on the bottom of the board was gone.  Amp was working fine after that.  My then got a new board from another local ham who did not need the pcb board anymore.  This was a new board. Last night I installed the new board but I was  blowing the fuse on the back, everytime I turned on the amp. Looking from the back side of the board, it was the left side fuse.  Took off the new board and the board was burnt a little on the bottom again. Finally, put the old board back on with the washer and made sure the wire on top of the choke was not touching the board except for the metal ring .  Any suggestions why the board was shorting or why I was blowing fuses?  Also does it matter how the board is oriented right on top of the tubes? I do not have any instructions on how to the board goes on.  How tight should the screw be that holds the pcb board to the choke?  Any suggestions would be great..
Thanks
John  KM5PS