This ended up on my bench... It had 3 bad tantalums; I replaced the fourth tantalum just because. All were replaced with Panasonic FC series aluminum Electrolytics.
C24 was bad, C20 and C27 were installed backwards (plus to minus). 

Also the first relay that switches between the xlr input and the front panel HiZ input was stuck. I replaced it with a Magnecraft TQ relay.

Seems reasonably happy now.
cheers