Ameritron AL-1500 Strange Issue

[Ranch55]

The gap is like a spark plug gap, hence the specified gap.
I am not sure , but I think it acts as some kind of safety or protection device.

"There is a voltage limiting gap built into my amplifier. This gap is designed to be the point at which any arcing will occur (harmlessly) if the tank voltage gets too high for any reason. It consists of a metal tab mounted to the hot side of the plate tuning capacitor. This tab is bent to create a specified gap to the grounded side of the tuning capacitor. For my amplifier, this gap should be set at about 0.11 inches, which is slightly less than the specified gap across the plates of the plate tuning capacitor. The 0.11 inch gap should limit the maximum voltage that can be developed across the plate tuning capacitor to about 4 KV. However, in my amplifier the gap was over 0.25 inches. This resulted in arcing always occurring across either the plate tuning capacitor or the output tank bandswitch."

 

[357]

I stumbled on this...

eHam.net

Arc Voltage Limiter

Never even knew it existed
I had to change the relay board and snapped some shots. No arcing like that link thank goodness

 

[357]

I had another look at my 1200 today and I see its arced in the past. I think it should have a washer on there before the tab is put on that stud. I'll have to clean that up and keep an eye on it.

 

[357]

.11" is 2.67mm I found an allen key that was pretty close and used it as a feeler gauge. A 1/8" drill bit is close to money too. Added some washers and I think its good. I did clean the area a bit too
You can see that tab has had some action.
I took pictures the day I got the amp and I see it was already toasty so I think it was the previous owner maybe loaded it too low or who knows but I'm glad I seen your post as I missed it on mine and it defiantly needed some attention.
73