Arcing at HT sucker cap

Arcing at the cap can be caused by something as simple as dirt/dust/crap under the cap. Discharge, remove the cap and wipe the entire back of the tube down with a microfibre cloth and isopropyl alcohol. Give the area under the anode cup a really good clean, then wipe it dry, then wait 10-15 minutes for it to be totally dry just to be sure. Then reconnect and see if it's still arcing. I have fixed three arcing monitors using this method, they just needed a clean.

 

However, the dimness is a worry, and might not be related to the arcing at all. Still, I'd clean first and then see what happens.

Clean the anode cap and the tube around the anode button with isopropyl as pat says, clean the lead carefully, gently sand down the shatter hook (metal clip that goes into the anode button) then gently sand the inside of the anode button with 800 grit paper (unless visibly rusty in which case go nuts) then, if still arcing, go and get some spark plug grease and line the outside rim underneath the anode cap.

Thanks guys I'll give that a go in the next couple of weeks.

Ok finally got around to cleaning the anode cap, hole and surrounding area. Now the visible arching has stopped, and the picture is back to normal (no longer dim). However there is a hissing/fizzing noise which seems to be coming from the anode cap. It might have been there while the arcing was occurring and I never noticed it. The monitor on the other side (of the twin cab) doesn't make this noise.

 

So is this hissing something to be concerned about? If so, any advice on how to resolve it?

 

I've refrained from running the monitor incase it could be causing damage.

The hissing/fizzing is just another arcing sound. It's not the audible crack that some arcing causes, but it's still arcing. Remove cap, clean again reseat cap. Move it around, ensure the suction cup is really firmly placed etc. I have one monitor that made this fizzing noise, even after multiple cleanings. Reseating and moving the cap around ended up fixing it. Obviously do not move the cap or go anywhere near it while the monitor is running :) Also ensure that you discharge the monitor before you do anything.

Need to put some dielectric grease around it too, and let the alcohol fully dry before you turn it on. Dry it very well with hot air, or it will just arc again.