After doing a lot of switching around between different MPU boards and different game chips. I have in fact confirmed that the sound chip in U49 must be there for sound to work regardless of which game chip is used. I do, in fact, need a sound chip. I will shoot you an email RB.

I have a few if you need one. You can borrow one from another board and confirm that it will make your board work.

I'm using Sp1137. Sounds like it needs the U49 chip.

I ordered and received a spare 10 mhz S+ MPU board. I went to tested it on a known good machine.
I installed the reel chip and went through the clear process and than put the the SP chips in and it booted up and plays but it has no sound.  Even when I did the reset there was no ding. I have checked/adjusted the volume wheel and the dip switch #3 in on and off settings. It does have reel stop sounds from the handle solenoid but no coin drop, winning or reel spin sounds.
 I put my original known good board back in and I have sound so there's something up with this board. Do you know what it could be? The board itself looks like it's missing a couple chips (U18 and U49) but I don't know if they're relevant or not too sound. Any help or guiance would be greatly appreciated.

It works with the new board! Any way to adjust the volume? I've tried to find it in the manual but no luck...