AMI Model H - Pulse convertor - Motor gets hot

I am a novice at fixing my jukebox (But am prepared to learn) and would hugely value anyones advice.

Every few weeks I hear a constant buzzing noise from the jukebox. (sounds like a relay buzzing - but not sure which one)

Symptoms are:
- Pulse convertor Motor gets VERY very hot.
- buzzing sound that is constant
- jukebox still works
- If I switch off and on problem goes away (No buzzing sound - )
- when problem occurs I switch OFF then ON again - I hear a relay click (which I dont normally hear when I switch on - in normal use ) then no buzzing sound and all works perfectly. (till the next time)


This is a difficult problem for me to find as it only happens every 6 weeks or so. I wondered if anyone had any thoughts on where I should look.
Thank you in advance for any guidance - I am grateful.
Best wishes Andrew