Can you hit it & get it to come & go ?
Watch any Sonys for cold joints especially around the hoz drive & out, vert IC
& the small 3 legged regulator IC's ( 12V, 9V, 5V etc.) .
Around shields also.
Try different inputs also. That may be a clue.
Electrolytics also a strong candidate. Most likely a surface mount.
A can of freeze mist can be a real friend on this one.
73 Zeno
LFOD !