Defender project revisited

[EVB]

After reading all that I would say you have made a lot of effort for not much reward.

You don't need to pull a logic probe out of your ass, you can simply make one with an led and a resistor so you can read an output/input high signal (+5) to test the PIA. You will need to make a test light, you will need the schematics so you can see what pin to monitor with your test light for each sound. You could also just skip that and remove the old PIA on the sound board, install a socket and plop a new one in there. The only issue is it could either be the PIA on the ROM board or on the sound board or both. I'd swap the one on the sound board first. That's my 25¢.

anyone? at all? it's Defender. you love Defender.

 

[mecha]

the latest and greatest in this project...

I was able to hotwire the game to the Sound Test, after which it played no sounds at all. I tried doing the jumper thing on the wiring harness between the rom and sound boards and got no sound that way either.

if anyone has any familiarity with those Williams-esque carryover test buttons that came with like Mortal Kombat 2 and various other Midway games, can one of those be rigged for test switches on Defender? the ones that are red and black... I suppose just like Defender. I don't really understand what the Auto Up and Manual buttons are supposed to be.... either I have circuit when I touch the Auto-Up to ground or I have nothing at all. wtf is the manual supposed to be? which one of these is supposed to be an on/off and the other's a momentary? I really should just order the buttons from Bob and shoehorn them into the Midway enclosure I have and be done with it heh. but does that include instructions on where to solder the wires to?

I also think now is a very important time to mention that I've seen it spark in the past, but while I was sitting in back of the cab trying to test the sounds, I heard the power switch arcing again. any suggestions on what to do about that?

what a debacle!

 

[MajorHavoc]

Replace the switch?

 

[mecha]

Replace the switch?

that's a good one.

what about the sound board issue though, is the PIA trash after all? as it stands right now, it plays sound during the game, just wrong sounds. I've replaced the connectors on the wiring harness that goes between the rom and sound boards, ran continuity checks, no bad wires.

 

[Dokert]

the latest and greatest in this project...

I was able to hotwire the game to the Sound Test, after which it played no sounds at all. I tried doing the jumper thing on the wiring harness between the rom and sound boards and got no sound that way either.

if anyone has any familiarity with those Williams-esque carryover test buttons that came with like Mortal Kombat 2 and various other Midway games, can one of those be rigged for test switches on Defender? the ones that are red and black... I suppose just like Defender. I don't really understand what the Auto Up and Manual buttons are supposed to be.... either I have circuit when I touch the Auto-Up to ground or I have nothing at all. wtf is the manual supposed to be? which one of these is supposed to be an on/off and the other's a momentary? I really should just order the buttons from Bob and shoehorn them into the Midway enclosure I have and be done with it heh. but does that include instructions on where to solder the wires to?

I also think now is a very important time to mention that I've seen it spark in the past, but while I was sitting in back of the cab trying to test the sounds, I heard the power switch arcing again. any suggestions on what to do about that?

what a debacle!

Auto (up) is switch NC and runs through all tests by itself
Manual (down) is switch NO and causes the user to switch between tests manually

Does that answer your question?

 

[mecha]

Auto (up) is switch NC and runs through all tests by itself
Manual (down) is switch NO and causes the user to switch between tests manually

Does that answer your question?

Yes sir.

What should i do about the sound board, replace the PIA or is there something else to look at too?

 

[LeChuck]

What should i do about the sound board, replace the PIA or is there something else to look at too?

What happens when you press the diagnostic switch on the sound board? That will help confirm the data paths from the sound CPU perspective. If that works, but manually grounding the PIA inputs doesn't, then it would seem the PIA isn't fully working (it has to be working somewhat to get any sound at all, even with the diagnostic switch). If neither works, there are more things to check on the sound board - CPU functionality, decoding, etc.

LeChuck

 

[mecha]

What happens when you press the diagnostic switch on the sound board? That will help confirm the data paths from the sound CPU perspective. If that works, but manually grounding the PIA inputs doesn't, then it would seem the PIA isn't fully working (it has to be working somewhat to get any sound at all, even with the diagnostic switch). If neither works, there are more things to check on the sound board - CPU functionality, decoding, etc.

LeChuck

Sound test switch plays a sound, im not sure what its supposed to sound like however, as the 2 sound boards i have tried sounded entirely different. Ive heard its supposed to be the 1up sound, but im not familiar with the game enough to even know what that is.

If you could just tell me what # sound it is in the sound test that would help, i can just listen to it in MAME. But it does play a sound when i hit the switch at least.

 

[LeChuck]

Sound test switch plays a sound, im not sure what its supposed to sound like however, as the 2 sound boards i have tried sounded entirely different. Ive heard its supposed to be the 1up sound, but im not familiar with the game enough to even know what that is.

If you could just tell me what # sound it is in the sound test that would help, i can just listen to it in MAME. But it does play a sound when i hit the switch at least.

Not sure if it changed over revisions, but mine plays sound 30 repeatedly when the diag switch is pressed. That should test the basic functionality of the sound CPU, ROMs, PIA, DAC, speakers, and other surrounding logic.

If you grounded the test pads on the ROM board and got no sound effects, you can try the same experiment on the sound board (just to rule out the ribbon cable and connectors). I don't recall there being test pads there, but you can use the pull-up resistors, or just do it right in the connector.

If the diag switch can play sound normally, but grounding the PIA sound select lines manually doesn't do anything, then I would suspect that portion of your PIA is faulty.

Just to confirm - are the sound select lines high (5V) when you're at a point where no sounds should be playing (e.g. self-test mode)? The PIAs usually interrupt the CPU based on falling edges, so just want to make sure it's seeing the high -> low transition.

LeChuck

 

[mecha]

Not sure if it changed over revisions, but mine plays sound 30 repeatedly when the diag switch is pressed. That should test the basic functionality of the sound CPU, ROMs, PIA, DAC, speakers, and other surrounding logic.

If you grounded the test pads on the ROM board and got no sound effects, you can try the same experiment on the sound board (just to rule out the ribbon cable and connectors). I don't recall there being test pads there, but you can use the pull-up resistors, or just do it right in the connector.

If the diag switch can play sound normally, but grounding the PIA sound select lines manually doesn't do anything, then I would suspect that portion of your PIA is faulty.

Just to confirm - are the sound select lines high (5V) when you're at a point where no sounds should be playing (e.g. self-test mode)? The PIAs usually interrupt the CPU based on falling edges, so just want to make sure it's seeing the high -> low transition.

LeChuck

yeah, it plays sound 30. the OTHER sound board I had before sounded like a friggin digital engine revving over and over... not even a sound in the game lol.

why the hell do these PIA chips go bad so frequently?

also, I tried grounding at the sound board connector with the connector plugged in, does that need to be unplugged? I just tapped some stripped wire to the exposed slots in the connector.

 

[LeChuck]

also, I tried grounding at the sound board connector with the connector plugged in, does that need to be unplugged? I just tapped some stripped wire to the exposed slots in the connector.

The lines are pulled high by both the sound and ROM boards, so it doesn't matter if the connector is in or not (as long as the sound board still has power). Just to prove your hypothesis another way, I would remove the connector and try the same experiment.

Can you also confirm that your sound select lines are high (5V) normally? I just want to rule out the possibility that the lines are stuck low, and the PIA is just not seeing the edges it needs to trigger the sound CPU interrupt. Since the diag switch works, the PIA has to be working to some extent .. so I'd like to actually prove it has failed.

If the sound select lines are low all the time, that could indicate a problem elsewhere (e.g. jumpers J19 and J20 could be set incorrectly on your sound board, pulling the lines low instead of high).

LeChuck

 

[mecha]

well, an update, finally.

I replaced the PIA on the sound board, and when I turned the game on the volume was on like full blast, startup sound, hotwired it to get out of test mode and BAM! the sound worked.

now I can finish re-wiring the coin door. and changing that nasty incandescent fixture out of the marquee with a fluorescent. and installing the lithium battery.

and maybe if I'm feeling dangerous, give every board a simple green bath.

 

[scottz29]

Since the diag switch works, the PIA has to be working to some extent .. so I'd like to actually prove it has failed.

Not sure why the PIA would have anything to do with whether or not your diagnostic switch works, but a logic probe will tell you which sound channels are not being pulled low on the PIA during the sound tests.

well, an update, finally.

I replaced the PIA on the sound board

 

[mecha]

I'll post pictures sometime if I get around to it. But I'll do it in the restore section.. there's some little odds and ends parts I have questions about.

 

[LeChuck]

Not sure why the PIA would have anything to do with whether or not your diagnostic switch works

Because all speaker output in the game comes from the data lines on one channel of the PIA. Pressing the diag switch and getting sound verifies that a large portion of that data path is working, incl. most of the PIA (manually grounding the sound select lines is an easy way to verify the other channel).

LeChuck

 

[mecha]

yeah, grounding the lines on mine produced NO sounds. I thought it was funny that sounds even played at all in the game, albeit totally wrong ones.