Space Invaders Sound question

I'm trying to fix a Midway Space Invaders sound board. The invader hit sound and saucer hit sound are both a high ring. I've replaced all the LM3900's and the 4016 in both circuits.

I'm thinking both problems are related. ftp://ftp.rossiters.com/pub/Daughterboard.tif

On pins 4 and 5 of LM3900's (M5) and (K5) there should be some sort of pulse, instead it's just a straight 12v line. Can someone explain to me what causes those pulses (when the board is working) and what I can check to get my sounds to work properly?

thanks!

Matt

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Received on Mon Dec 29 04:31:11 2003