Buzzing sound in Commodore 1084

[qq1975b]

Hello, I have a Commodore 1084S since recently that I have changed all the capacitors. However, the other day I turn it on and I hear it make a noise, a buzz for about 1 min. Once it disappears, it does not reappear until the monitor cools down. I decided to open it and the sound is coming from the tube itself. I swapped out the board and PSU with another 1084 I have and the sound is definitely coming from the tube. The image looks good, but when you turn it on when it is cold, it makes that noise during that min, min and a half approx. Sometimes it doesn't appear until few minutes has passed.

Can someone tell me what could be happening? should I be worried?

Thank you very much.

 

[levo-ace]

just offthe top of my head ( i cannot hear the noise myself because of industrial noise damage ) , however if it has a de-gaussing coil it could be that as the degaussing circuit only comes on for a short while to de-magnetise the screen . If it does not then the magnetic plates may have developed a small gap that allows them to vibrate until they have warmed up. The clamp holds the plates in place , If you decide to try and tighten the plates together ( undo the clamp and push them together and then do it up ) be very careful as the orientation of theses guides the electron beam to the right place from the guns .

 

[qq1975b]

Oh, sorry to hear that. I have tinnitus that is quite annoying but nothing compared to hearing losing. Thank you for your reply. I will take the cover out, discharge the monitor and see if something seems a little bit loose.

 

[Dano]

Also possibly a bad connection of the HT lead to the tube.