Hi Shaun,
Q801/2 on the long central heatsink have very small solder pads and often develop dry joints. If so, scrape away some of the paint around the joints and resolder them, making sure they're not shorted first. Check smd components near these FETs, R802/3 and RX832/3 (all 20 ohm). R803 is across R832 = 10 ohm combined. Others to check are RX804 (10K) and DX803/4 (KDS184 or 1S184 or HSMS-2812)
Presume CX816/9 were among the bulged ones. If in doubt, the 2 larger FETs on the other end of the heatsink have an identical circuit to compare with. See how you go with that for starters. Bruce