The sound should be same on yellow target hits until 1 thru 7 targets and the 8 ball have been dropped, then their sound should change, so you are missing the first sound.

The sounds you're missing are produced by the AY3-8912 audio chip at location U12 on the S&T board. So concentrate on diagnosing that section. Make sure the five EE jumpers below U12 are not installed.

The input side of the AY3-8912 is working - all commands sent to the S&T from the MPU board go through it.

Move onto the audio output trail of that U11 chip. It goes via test point TP7 through a switched filter and onto an op-amp at U13 configured as a low pass filter.

When you hit those Deluxe standup targets and there's no sound:
- Do you see any audio activity on test point TP7 (i.e. is the AY3-8912 outputting an audio signal) ?
- What happens on pin 19 of U11 (i.e. it activates the switched filter at transistor Q2 and might be causing it to filter too much)?
- Are you getting any audio activity at the input of the op-amp (pin 3 of U13)?
- Are you getting any audio activity at the output of the op-amp (pin 4 of U13)?

Excellent!

If you have an ESR meter, it'll probably tell you the capacitor is bad. There's another 2uF cap on the S&T board - good chance it's going bad too.

The sounds you were missing are generated by that PSG (Programmable Sound Generator) AY3-8912 chip.
Besides the TMS5200 speech chip, all other sound effects are generated through the Digital to Analog Converter (DAC) chip at U10 which in your scenario is working ok.

The capacitor you changed merges the AY3-8912 audio signal with the DAC audio signal.

This is a case where I used PinMAME to find out which chip generates those sounds you were missing. PinMAME allows you to separately adjust the volume of the three sound devices (TMS5200, DAC and AY3-8912) on the S&T. When I adjusted the AY3-8912 to 0% volume I could see the issue you described

Thanks for the post, recently picked up an ebd and the same exact sounds are missing, though I can ever so faintly hear the game over matching sound, I suspected a bad cap. Now I know where to eye ball

May I jump in here please? My EBD is doing the opposite. The only sound I have IS the yellow standups! No background sound, nothing from the drops or the slings, just the yellow standups. However, when shooting the standups going for DELUXE, there is NO sound from them. When I say there’s NO sound, there actually is. It’s just very, very faint with the volume turned all the way up. You have to listen real close to hear it. Speech works fine. Anything I can try without having too good a skill set?

So in your case the issue is more likely to do with the Digital to Analog Converter (DAC) sounds that come out of the U10 chip. The respective capacitor used to merge its audio signal is C43 which is a 2uF 25V capacitor. Replace it with a 2.2uF cap which is more commonly available. It's ok to get a higher voltage rated cap, but never go lower voltage. Note these electrolytic capacitors are directional; one leg is positive, the other leg is negative and they must be installed in the correct orientation. The board marks which is the positive "+" side and the capacitors themselves usually mark which is the negative leg.

In fact you're probably better off getting a capacitor kit and changing them all on this board - the caps on these S&T boards are known to go bad. It's up to you.

If replacing the capacitor doesn't fix it, you might have a faulty AD558 DAC chip at U10 or circuitry surrounding it.
Good luck!

Look in the manual for background sound settings. I don't know why would work and the other wouldn't but many of my S&T boards will not play BG sound until I set it. Don't have the EBD manual but for Embrypon it is #18 setting to "03"