Hijacking your thread as I have a different sound problem...
I have a Midway Space Invaders with the latest Phil M test rom that has put up a real fight...
At power up, a sound starts (much like the ufo but other sounds too) and this sound continues until any one of the E5 sounds is triggered.
Sure enough, at boot all outputs of E5 are high so all of those sounds are being generated at once. Once I trigger any 1 of those sounds, all of the outputs return to low.
All of the sounds then work normally.
At one point, I could get it to start again if I wiggled the daught in the socket. But I have replaced the socket on the motherboard and fixed all the fingers on the daughter board.
This only happens on E5 (which has been replaced) and not E4, so I don't think it is a data line issue nor reset. In reading about the 74ls174, it seems like the timing of the port 5 signal determines when the data lines are read. But since all port signals are generated by E3 and all the other ports are working correctly, I don't think the Sample is bad.
So that leaves the address lines A8,A9 & A10.. but even if 1 of them was getting bad data, why wouldn't that show up on other ports?
I'm especially puzzled why the reset at boot doesn't reset this chip.
I should also mention that I just started to get in the shifters...
I'm out of ideas...