LyonsArcade
Well-known member
Purists, beware. Purists, run for cover. Those who are squeamish, read no further 
I've got a Spy Hunter upright, with the 'buzz' problem on the lights. If you've never experienced this phenomenon, on SOME Spy Hunters (I had one before that didn't do it!) there's an issue where when the lights come on (weapons van, missles, oil slick, etc.), there's a 'buzz' in the audio that comes along with it. Since the lights blink, the buzz goes on and off, on and off. On my machine, it was REALLY loud, I mean, can't hear the game play it's so loud, loud. I mean "RUN, COWARD!!!!!" loud. LOUD.
Anyways, it seems like this is a pretty common problem, so I felt sure I could fix it. First, I rebuilt the stock power supply with a kit from Bob Roberts, connectors and all... while that gave me really good voltages out of it, it didnt' fix the problem. I tried cutting the jumpers on the power supply, didn't fix the problem. I tried the power supply out of my Tron... didn't fix the problem. I bit the bullet and replaced the two big caps in the power block, didn't fix it. I recapped the light board, didn't fix it. Recapped the Cheap Squeak, didn't fix it. Added ground wires, removed ground wires, nothing fixed it. Recapped the sound amp, didn't fix it. Tried seperate cheap squeak, light pcb, and sound amp boards one at a time. Didn't fix it!
Basically, some of these machines have a little monster hiding in them that makes this happen and the best I can tell, nobody's figured out why. It has something to do with the audio and the switched lights being on the same 12volt unregulated source out of the power supply. This is supposed to be seperate from the logic 12 volts, but still the buzz happens because as soon as enough light bulbs light up, it makes the audio buzz.
After trying all this, I set out to HACK the game today to make it work right. The first thing I tried was, if you look the 12volts that run the 6 light bulbs (I'm leaving the coin door bulbs hooked up how they were for now)... the 6 light bulbs get their 12volts off of the light board. What I tried was cutting the trace on the back of the light board, and bridging the 12volt output to the bulbs to the 5volt line coming in from the power supply, and powering the chips on the light board. The reasoning behind this was, if the lights weren't on the audio's 12volts, it wouldn't buzz. So I tried it.
That made the bulbs stop buzzing. As soon as I did that and put it back together, after swapping the bulbs out with 555's (5 volt bulbs)... you could play the game, and the buzz was gone when the lights came on! Only problem was, now you were putting the lightbulb 'load' on the logic's 5volts! So as soon as 4 bulbs came on... the game crashed and reset. I tested the power supply to see what was happening, the bulbs ALL on at the same time dropped the power supply voltage at the CPU to 4.6 volts... and of course it would reset that low.
So, next, I decided to run the light board off of a seperate power supply. I left the light board hacked how I had it, and cut it's 5volt supply off... then connected it to a seperate switcher, which I wired into the a/c wiring going to the marquee light. I tried it, and the bulbs wouldn't work. So I studied the board and those same chips get a ground signal too of course.. I took that ground loose, and swapped it over to the power supply, and Voila!
Now the game plays great, all the lights work, no buzz when the bulbs come on.
So the way it's set up right now :
1. The coin door bulbs are still hooked up to the audio circuit. You could swap these over to a 5 volt source if you wanted, or maybe even run them off the 6.3a/c that's on the transformer, but I think you'd have to redo the ground wire if you did that to run it back to the transformer as well. My machine wasn't loud enough with the bulbs installed in the door for it to matter, so I left them.
2. All the bulbs on the other 6 sockets were switched to 555's, so they'll run on 5volts.
3. On the back of the light pcb, I cut the heavy trace running to the 12volt output pins... these are pins 5 and 6. Cut the trace just outside of the pins, so that the two pins (and the wires that plug in!) are on their own little 'island' and not connected to the rest of the board. The trace is thick and will take some work to get it cut away. This isn't a huge deal, because you could 'rebridge' it and put it back how it was in the future if you'd like.
4. Bridge pins 5 and 6 to pins 3 and 4, which is where the 5 volts is coming into the pcb. Once that's done, you've got 5 volts running to the 6 bulb sockets instead of 12v... the 5 volts is still hooked up powering the board, and also now powering the 6 light bulb sockets.
5. Cut the red/yellow wire running from the light pcb, back over to the Cheap Squeak... that's where it gets it's 5 volt supply from. Don't cut the wrong wire, the wire runs from the power supply, through the cheap squeak connector, and back over to the light pcb... cut it AFTER it runs to the Cheap Squeak. Look closely and you can see which one runs to the cheap squeak, and which is coming back. The Cheap Squeak should be still hooked up how it was, and to the original power supply when you're done.
6. Connect that cut red/yellow wire (still attached on one side to the light pcb) to a 5v switching supply. If you pull it out of the loom all the way over where it attached to the cheap squeak, you'll have 3 feet of wire to mess with.
7. Cut the white/yellow wire where it leaves the power supply and heads over to pin 11 of the light pcb. Leave the wire a little long in case you ever want to reconnect it, it'll be easy to splice back together.
8. Connect that cut white/yellow wire to the ground on the switcher.
9. Connect the a/c input of the switcher to the wiring controlling the marquee light... this can be done easily at the 12 pin plug on the left side of the power brick in the bottom of the cabinet. One wire is Blue and orange, the other is Brown and White. There are two brown and white wires, make sure you grab the one that goes to the marquee, so it'll be switched instead of on all the time.
Turn on the game, and enjoy playing it with no buzzing lights!
Disclaimer: If you do this, and your house burns down, I am not responsible. Do this at your own risk! There may be an easier way to do it (such as leave the 12v hooked up to the bulbs, and hook up a seperate 12 volt supply.. I had an extra 5v 'only' switcher)... but this is the way I did it.
You'll notice the 12 volt is still hooked up to the light pcb, and there's another yellow ground wire still hooked up as well. This is actually still running the two 'switching' chips on the board, which ground out the light bulbs to make them turn on and off. I think if you disconnected that 12volt the lights wouldn't work any more. The 5v you hack in is running all the chips on the board as well, and the light sockets. The yellow/white ground runs the two chips that switch the grounds on and off, and the yellow/green ground runs the U1 chip. So you have to leave everything hooked up, if one thing isn't there the board won't work.
I've got a Spy Hunter upright, with the 'buzz' problem on the lights. If you've never experienced this phenomenon, on SOME Spy Hunters (I had one before that didn't do it!) there's an issue where when the lights come on (weapons van, missles, oil slick, etc.), there's a 'buzz' in the audio that comes along with it. Since the lights blink, the buzz goes on and off, on and off. On my machine, it was REALLY loud, I mean, can't hear the game play it's so loud, loud. I mean "RUN, COWARD!!!!!" loud. LOUD.
Anyways, it seems like this is a pretty common problem, so I felt sure I could fix it. First, I rebuilt the stock power supply with a kit from Bob Roberts, connectors and all... while that gave me really good voltages out of it, it didnt' fix the problem. I tried cutting the jumpers on the power supply, didn't fix the problem. I tried the power supply out of my Tron... didn't fix the problem. I bit the bullet and replaced the two big caps in the power block, didn't fix it. I recapped the light board, didn't fix it. Recapped the Cheap Squeak, didn't fix it. Added ground wires, removed ground wires, nothing fixed it. Recapped the sound amp, didn't fix it. Tried seperate cheap squeak, light pcb, and sound amp boards one at a time. Didn't fix it!
Basically, some of these machines have a little monster hiding in them that makes this happen and the best I can tell, nobody's figured out why. It has something to do with the audio and the switched lights being on the same 12volt unregulated source out of the power supply. This is supposed to be seperate from the logic 12 volts, but still the buzz happens because as soon as enough light bulbs light up, it makes the audio buzz.
After trying all this, I set out to HACK the game today to make it work right. The first thing I tried was, if you look the 12volts that run the 6 light bulbs (I'm leaving the coin door bulbs hooked up how they were for now)... the 6 light bulbs get their 12volts off of the light board. What I tried was cutting the trace on the back of the light board, and bridging the 12volt output to the bulbs to the 5volt line coming in from the power supply, and powering the chips on the light board. The reasoning behind this was, if the lights weren't on the audio's 12volts, it wouldn't buzz. So I tried it.
That made the bulbs stop buzzing. As soon as I did that and put it back together, after swapping the bulbs out with 555's (5 volt bulbs)... you could play the game, and the buzz was gone when the lights came on! Only problem was, now you were putting the lightbulb 'load' on the logic's 5volts! So as soon as 4 bulbs came on... the game crashed and reset. I tested the power supply to see what was happening, the bulbs ALL on at the same time dropped the power supply voltage at the CPU to 4.6 volts... and of course it would reset that low.
So, next, I decided to run the light board off of a seperate power supply. I left the light board hacked how I had it, and cut it's 5volt supply off... then connected it to a seperate switcher, which I wired into the a/c wiring going to the marquee light. I tried it, and the bulbs wouldn't work. So I studied the board and those same chips get a ground signal too of course.. I took that ground loose, and swapped it over to the power supply, and Voila!
Now the game plays great, all the lights work, no buzz when the bulbs come on.
So the way it's set up right now :
1. The coin door bulbs are still hooked up to the audio circuit. You could swap these over to a 5 volt source if you wanted, or maybe even run them off the 6.3a/c that's on the transformer, but I think you'd have to redo the ground wire if you did that to run it back to the transformer as well. My machine wasn't loud enough with the bulbs installed in the door for it to matter, so I left them.
2. All the bulbs on the other 6 sockets were switched to 555's, so they'll run on 5volts.
3. On the back of the light pcb, I cut the heavy trace running to the 12volt output pins... these are pins 5 and 6. Cut the trace just outside of the pins, so that the two pins (and the wires that plug in!) are on their own little 'island' and not connected to the rest of the board. The trace is thick and will take some work to get it cut away. This isn't a huge deal, because you could 'rebridge' it and put it back how it was in the future if you'd like.
4. Bridge pins 5 and 6 to pins 3 and 4, which is where the 5 volts is coming into the pcb. Once that's done, you've got 5 volts running to the 6 bulb sockets instead of 12v... the 5 volts is still hooked up powering the board, and also now powering the 6 light bulb sockets.
5. Cut the red/yellow wire running from the light pcb, back over to the Cheap Squeak... that's where it gets it's 5 volt supply from. Don't cut the wrong wire, the wire runs from the power supply, through the cheap squeak connector, and back over to the light pcb... cut it AFTER it runs to the Cheap Squeak. Look closely and you can see which one runs to the cheap squeak, and which is coming back. The Cheap Squeak should be still hooked up how it was, and to the original power supply when you're done.
6. Connect that cut red/yellow wire (still attached on one side to the light pcb) to a 5v switching supply. If you pull it out of the loom all the way over where it attached to the cheap squeak, you'll have 3 feet of wire to mess with.
7. Cut the white/yellow wire where it leaves the power supply and heads over to pin 11 of the light pcb. Leave the wire a little long in case you ever want to reconnect it, it'll be easy to splice back together.
8. Connect that cut white/yellow wire to the ground on the switcher.
9. Connect the a/c input of the switcher to the wiring controlling the marquee light... this can be done easily at the 12 pin plug on the left side of the power brick in the bottom of the cabinet. One wire is Blue and orange, the other is Brown and White. There are two brown and white wires, make sure you grab the one that goes to the marquee, so it'll be switched instead of on all the time.
Turn on the game, and enjoy playing it with no buzzing lights!
Disclaimer: If you do this, and your house burns down, I am not responsible. Do this at your own risk! There may be an easier way to do it (such as leave the 12v hooked up to the bulbs, and hook up a seperate 12 volt supply.. I had an extra 5v 'only' switcher)... but this is the way I did it.
You'll notice the 12 volt is still hooked up to the light pcb, and there's another yellow ground wire still hooked up as well. This is actually still running the two 'switching' chips on the board, which ground out the light bulbs to make them turn on and off. I think if you disconnected that 12volt the lights wouldn't work any more. The 5v you hack in is running all the chips on the board as well, and the light sockets. The yellow/white ground runs the two chips that switch the grounds on and off, and the yellow/green ground runs the U1 chip. So you have to leave everything hooked up, if one thing isn't there the board won't work.