I picked up a really nice Black Knight Project. Boards are super clean and with some minor adjustments most everything is working with a few exceptions.

I cannot get the game to hold memory. It boots to 2500 3. I can force the game to start by opening the coin door and turning the machine off and on a couple of times. I have checked the battery holder and board and they both look really clean. No battery acid damage or bad traces that I can detect.

The second issue is the sound. The game has not sound either in diagnostic sound test or in game. Voltages on the sound board are correct. i double checked all connections and they look good.

The last issue is the coin door. I am not getting voltages to the coin door lights. I do not show continuity from the white/yellow plug connector on the driver board to the white/yellow connector in the cabinet.

I will check the power on the chip.

I do get an audio thump/buzz when starting the game.

I don't think it is the sockets because I am not detecting voltage to the sockets.

Quick update. No sound is produced from pushing the test switch on the sound board.

Yes, i have adjusted the volume both in the cabinet and on the board and still no sound. i will try your other suggestions tonight. When you say CPU sockets do you mean those on the sound board?

Yes, I have the smaller voice board connected to the sound board via the ribbon cable.

I replaced the battery holder - I had a spare that was good. This seems to have solved the memory problem - pin boots now to attract mode. However, it caused a new problem. I cannot get into diagnostic mode. The diagnostic switch is now not working. Strange because it was working prior to changing the battery holder when the pin was booting into diagnostic mode.

I haven't had a chance to check the sound issue.

Diagnostics now working. It was a connector as you suggested. I will work on the sound next.

The test switches and blanking led on the MPU don't work. Game is booting fine and enters a game fine. When I pulled the board I noticed that the IC just above the batteries had some corrosion on the legs - it is IC 24 a 7400 nand gate IC. It looks like the test and blanking go through that IC. I am wondering if that could be the problem.

I could also use some advice on the displays. There are three displays - two player and the credit and ball display - and two missing player displays. The three displays work fine. I can purchase a full set of LED displays for what I can purchase 2 original plasma displays. What are your thoughts on keeping everything plasma versus going LED. I am leaning toward the latter.

I have been trouble shooting the problem of no sound.

I thought the problem was with IC10 on the sound board. Legs 22-36 pulse correctly on ic10 but legs 2-9 do not pulse and are locked eother hi or lo. I replaced ic10 with a new PIA and I still have the same issue. Legs 22-36 pulse correctly but legs 2-9 do not pulse.