LOUD Subwoofer POP whe powering on speaker
I'm sorry that the combo popped the amp. Looking over your diagram, it seems that the speaker terminal to delay board looks good, assuming that you aren't paralleling the Left and Right outputs.The power connection is where I am not sure exactly what you are doing. Usually, only the positive comes off the switch, and the negative connects to the power jack's ground trace. That board is very hard to follow.
What I would do, while awaiting the replacement amp, would be to try to trace the power from the jack through the switch. All you'd need is a continuity meter for that. Luckily, even the cheapest DVM's have that capability. Put your meter to the lowest Ohm setting and touch the leads together, the meter should beep. Now comes the tricky part. With the amp Power Switch set to OFF, touch the center pin of the power jack (+) and touch the 3 terminals of the switch. 1 terminal should beep, that's the V-in to the switch. Theoretically, the other 2 terminals should stay silent. Now set the switch to ON and check the terminals that were silent. 1 should beep. That is the switched VCC that you want to use to power the (+) of the Delay board. Now, move from the center pin of the Power Jack to the side contact (-), it'll be tight. On the back side of the Amp board, find the ground pin of the jack, it'll be the one beeping. Use that for your ground (-) of the Delay board.
You should be able to test out the power wiring using the old amp board. With JUST the power wires connected between the amp and delay, connect the 19V power supply to the amp. Then switch it on. You should hear the relays click on after a second or two. If that works, you can be pretty confident you've figured out the correct wiring points for power.
When you get the new amp, follow the same procedure, checking along the way. Better to catch a problem early in the steps than to go through the whole connection process only to have an error - easier to fix a little work rather than a whole lot. 😊