My New Missile Command has a Few Issues (trackball, audio)

amplibax

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My New Missile Command has a Few Issues (trackball, audio)

http://forums.arcade-museum.com/showthread.php?t=377083

I posted about my Missile Command above. I figured I should move the technical discussion here to get some help.

So since I last posted in that thread I removed the Super Missile Attack add on PCB and I was able to get into the test mode and it passes all tests.

There was an issue with the video being inverted vertically. The yoke connector was connected normally but I decided to flip the vertical yoke connectors and that has fixed that issue so for now.

My remaining issues are:

-no audio
-trackball not working

#1 No audio
I am going to see if I can get a hold of a Pokey chip to swap in for the audio to see if that fixes it. One thing to note is that when I turn up the speaker volume there is a hum.

#2 Track Ball not working
For the trackball I can't find too much info other than one thread that stated I could try replacing the 74LS157 at D9. I have a parts board with some HD74LS157P. Would these work?

I noticed that in test mode when I press player 2 start, the cursor moves to the left a bit... not sure if that's normal.

If anyone has any suggestions I would welcome them! Thanks
 
Trackball try replacing mc14574 @ c9
Sound try replacing the lm324 @ n10

Yes a hd74ls157p will work for the 74ls157

As long as it's got 74ls157 in the definition it's fine the hd is the manufacturer the p means plastic
 
I ended up sending the board to Jason in Ontario who was nice enough to offer to take a look at the board for free.

He replaced two inverter ICs and the Pokey (apparently the one I had in there was the wrong version). This fixed the board for him and he said he played it in his machine for 30 minutes.

So I got the board back the other day and I'm getting the same issues again plus language on the board is now Spanish even though it has the dip switch for English set.

He suggested it could be a short or an open ground on my wiring harness that blew the Tao ICs again. Any thoughts?
 
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