Unplug the speaker until we have the power amp working correctly.
2SD88A looks to be ok as a replacement, 300V TO-3, NPN, but only 5A collector current, 2N3055 woudl also work. If you are running into 4 ohm loads, i would parallel two output transistors insetad of using just one.
Meaure collector to emitter on all transistors, any shorted, check Base to emitter on diode range, all of them around 0.6V
If you can heatsink them, MJE340 & MJE350 are good for the driver transistors if any of the 40409 / 40410 are blown.
Is R314 (1k 2W) ok. Something is pulling one end of R313 down giving us excess dissipation & blowing it up.
remove the power transistors and power up, do you get approx 40VDC on the output ?
If the amp is fairly old, i would replace the speaker output electrolytic capacitor & the power supply caps, actually just do them all.