Peterson amp playing up again - thoughts?

[Pea Turgh]

Hello peeps.  Had my trusty (40+ years old) Peterson P120 combo for 16 years now.

 

Gigged it quite a bit, serviced a few years ago when it went thin and farty, returned to full health and had light use since.

 

Used it last night for a jam with my lad - all good.

 

Switched it on this afternoon - super loud low buzz, even with all controls at zero, with both instrument plugged in and not.  Power plug fine, briefly tested with 2 different basses, 2 different leads - no difference.

 

Might any knowledgeable folks recognise the fault from that symptom set?

[Bigguy2017]

Loose earth somewhere or dead smoothing cap?

[Pea Turgh]

Will open it up for a look (but not touch anything).

 

I won’t be switching it on til either;

A.  I spot something obvious and within my skill set, or

B. a tech sorts it for me - saw a powered wedge fail quite spectacularly whereby somehow DC went to the speaker 😱. Wouldn’t want that happening to old Pete!