My Black Knight is acting strange. When I turn the game on I could not start a game, but the flippers were working when I pressed the buttons. I hit the reset button on the MPU board and could put credits on the game, but it was playing some kind of sound continually. I took the following test point readings:

TP1 = 12.8
TP2= 4
TP3 = .47
TP4 = 3.9
TP5 = 4.9
TP6 = 2.5
TP7 = 5
TP8 = 5
TP9 = 5.1

I've already replaced all capacitors and IC sockets. I'm wondering if I have a bad transistor? Any idea where I should begin looking?

Are you talking about this capacitor? Where do I find a replacement?

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