andrewb
Well-known member
How To: Modify an Asteroids PCB for use in a Deluxe cab
I've had an Asteroids Deluxe (AD) cab for awhile, and recently got some non-functional Asteroids boards, which I wanted to repair and be able to play in my AD cab.
After doing some research, I found there is a lot of info about swapping Asteroids and AD boards between their respective cabs. There are harness mods, adapter boards, ROM mods, and multigame kits, but I hadn't found any posts fully documenting how to straight up mod an Asteroids board to run in an AD cab. So, I figured I'd post something here, for anyone wishing to do the same.
Disclaimer: I realize there are other ways to do this, and some people have issues with folks modifying boards (versus building harness adapters, etc), but in my opinion this method is relatively simple, and is easily reversible, so no irreparable harm is done to the board. Some of the other options might be easier and more desirable to some people who have the appropriate tools (e.g., ROM burners, etc). But for folks who only have a soldering iron and some time, this method is a pretty good option.
To be clear, this mod is meant for people wishing to run an Asteroids board in a stock upright AD cab. It involves making 3 modifications to the Asteroids PCB, which will allow it to plug-and-play directly into the AD cab, with no mods to the cab.
Also, if you do these mods, you should LABEL THE BOARD as such, so that anyone else knows, particularly anyone doing work on the board in the future.
Intro:
It turns out that you can plug an unmodified Asteroids board into an AD cab as-is, and basically play it. It will power up, and you can put it into test mode, coin it up, and play. However some of the controls are not mapped to the proper cabinet buttons, so pressing Player 1 or 2 Start will actually coin up the board (and make the coin counter click), and you have to activate the left coin switch to start a Player 1 game. (Also, the Player 2 start from the PCB does not map to any of the cab controls, so you can't play a 2-player game. I think it'actually maps to the center coin slot, which isn't connected in most cabs. Or at least that's how it was in mine.)
Also, because AD is designed to be played off of a mirror inside the cab (and Asteroids is not, i.e. you just look directly into the monitor), a stock Asteroids board plugged into an AD cab will appear upside down by default. However, because the left and right rotate buttons are also reversed between Asteroids and AD boards, you can actually play the game somewhat 'normally', in that the ship will rotate left and right as expected, and you can thrust, shoot, and hyperspace normally. It's just that the entire screen is upside down (e.g., score/text and saucers), so it's a little odd, given that the controls move you in the expected direction.
Also, the sound works, but the volume is a little low, so you don't get the full rumble and crashing of the sound effects. But you actually get 80% of the gaming experience with zero modifications, which is kind of neat, though I found myself wanting after a while to have it be 100%.
Setting out to fix these issues, it turns out there are 3 main modifications that need to be done:
1) Flip the Y-axis of the video output, so the image displays properly off of the mirror.
2) Remap the control signals to the proper cab switches.
3) Modify the audio output amp to boost the volume.
These 3 modifications turn out to be pretty easy to do, and can be reversed if needed. We'll handle each one separately.
Mod 1: Flip the Y-axis of the video output.
Asteroids Deluxe and (some other vector boards) actually have control signals on the edge connectors that can flip the X and Y axes of the output video signal. This is mainly used for cocktail cabs, where the harnesses are designed so that these pins are configured differently in the cocktail harness, which the board can detect, and flip the image when needed in cocktail mode.
An Asteroids Deluxe PCB actually has separate edge connnector control pins for inverting the X and Y axes independently. However, Asteroids only has one pin, which flips BOTH the X and Y axes at the same time, therefore it alone cannot be used to accomplish what we need.
However these inverting mechanisms basically manipulate a pair of DC voltages (+8.2 and -8.2V) on the PCB, which are connected to pins on a couple of switch IC's in the video output section, for both the X and Y axis outputs. If you reverse these voltages for either axis' switch chip, that axis flips. For AD and some other vector boards, the axes can be controlled separately. However because for Asteroids these two controls are tied together, we must cut them and manually swap the voltages for just the Y axis, which will flip the screen the way we want.
There are multiple ways and places to do this on the board, but I believe the simplest is right where the two signals leave the X-axis switch, and head toward the Y-axis switch. This is the MC14016B chip at location D13, shown in the picture below. You can make two small cuts in the traces leading away from the chip (shown in red in the pic below), and solder small wires from each IC pin to the opposite trace (shown in blue). Doing this here is convenient, because there's room to access the traces, and if you ever want to undo the mod, you just remove the wires, and solder over the cuts with a tiny bit of solder, restoring the original traces.
After swapping these two lines, you should see properly displayed video in the mirrored display.
Mod 2: Remap the PCB control lines to the proper cab switches.
The second modification is to fix the mapping of the controls, by modifying the signal paths on the Asteroids board. It turns out this is very easy to do.
Each control signal comes into the PCB via the edge connector, via a separate pin. For Asteroids, each signal goes through an inductor before going into an LS251 mux IC, which connects to the data bus. The inductors are all aligned in a row on the PCB, near the edge connector. This is the easiest place to remap the signals to the desired places.
There are 3 pairs of signals that need to be swapped around. And it turns out (at least on my PCB), that they are all right next to each other, in the row of inductors. You will need to make the following swaps:
Swap the L5 and L6 signals (COINL and START2)
Swap the L7 and L8 signals (COINC and START1)
Swap the L9 and L10 signals (ROT LEFT and ROT RIGHT)
You can just desolder and lift one side of each pair of inductors, then move one inductor to the opposite hole, then you'll have to solder in a short piece of wire (e.g., a piece of lead wire from a resistor) to connect the other inductor to the opposite hole, as shown in the pic below, for the 3 pairs of signals.
After swapping the 3 pairs of signals, your controls should operate properly.
Mod 3: Modify the audio output amp to boost the volume.
The final modification involves modifying the audio amplifier circuit, to boost the volume of the audio signal that is sent to the AR board (where it is amplified further, to drive the speakers). You only have to do this if you are unsatisfied with the low volume that occurs by default, but it's super simple, and worth doing IMO, as the playing experience is much better at full volume, especially in the AD cab.
Note that this mod assumes you are using a stock Asteroids Deluxe AR-1 power supply board in the cab. Asteroids and AD used slightly different AR boards, where the Deluxe AR had modifications to support the higher output signal from the game PCB, and used different (larger) 3300uF coupling caps instead of 1000uF, which changed the low-frequency response. This mod basically changes one resistor on the Asteroids PCB amplifier circuit, to make it similar to the AD circuit, and more compatible with the AD AR. If you are using an Asteroids AR, you do not have to do this mod (however that defeats the purpose of having it be a plug-and-play PCB swap.)
If you compare the audio output amplifier sections between Asteroids and AD, they are very similar. The primary difference is the gain of the main stage. These circuits use LM324 op-amps, which in the configuration used on these boards, have a feedback resistor that determines the gain. If you look at R86 on the Asteroids circuit, it is 1K ohms, while the equivalent resistor in the AD circuit is 10K ohms. All you have to do is replace resistor R86 with a 10K, and the Asteroids board will output a stronger signal.
The resistor is right below the LM324 op-amp chip, at location P12. It is circled in the image below. Just replace it with a 10K, and your volume should be at full level in the AD cab.
Summary:
This writeup is actually longer than the actual procedures require, but I wanted to include additional detail, for those who are curious about the 'why' of what is being done, and also to aid people in cases where the boards may be slightly different than my Rev -06 PCB which I did this on (though I don't expect the sections of interest to be significantly different between revisions.) In the end however, the mods can be done pretty quickly, and Asteroids (in my opinion) looks pretty damn cool through the electric blue mirrored display of the AD cab.
Good luck modding your boards, and feel free to PM me or post here with any questions. Comments welcome.
Regards,
Andy
I've had an Asteroids Deluxe (AD) cab for awhile, and recently got some non-functional Asteroids boards, which I wanted to repair and be able to play in my AD cab.
After doing some research, I found there is a lot of info about swapping Asteroids and AD boards between their respective cabs. There are harness mods, adapter boards, ROM mods, and multigame kits, but I hadn't found any posts fully documenting how to straight up mod an Asteroids board to run in an AD cab. So, I figured I'd post something here, for anyone wishing to do the same.
Disclaimer: I realize there are other ways to do this, and some people have issues with folks modifying boards (versus building harness adapters, etc), but in my opinion this method is relatively simple, and is easily reversible, so no irreparable harm is done to the board. Some of the other options might be easier and more desirable to some people who have the appropriate tools (e.g., ROM burners, etc). But for folks who only have a soldering iron and some time, this method is a pretty good option.
To be clear, this mod is meant for people wishing to run an Asteroids board in a stock upright AD cab. It involves making 3 modifications to the Asteroids PCB, which will allow it to plug-and-play directly into the AD cab, with no mods to the cab.
Also, if you do these mods, you should LABEL THE BOARD as such, so that anyone else knows, particularly anyone doing work on the board in the future.
Intro:
It turns out that you can plug an unmodified Asteroids board into an AD cab as-is, and basically play it. It will power up, and you can put it into test mode, coin it up, and play. However some of the controls are not mapped to the proper cabinet buttons, so pressing Player 1 or 2 Start will actually coin up the board (and make the coin counter click), and you have to activate the left coin switch to start a Player 1 game. (Also, the Player 2 start from the PCB does not map to any of the cab controls, so you can't play a 2-player game. I think it'actually maps to the center coin slot, which isn't connected in most cabs. Or at least that's how it was in mine.)
Also, because AD is designed to be played off of a mirror inside the cab (and Asteroids is not, i.e. you just look directly into the monitor), a stock Asteroids board plugged into an AD cab will appear upside down by default. However, because the left and right rotate buttons are also reversed between Asteroids and AD boards, you can actually play the game somewhat 'normally', in that the ship will rotate left and right as expected, and you can thrust, shoot, and hyperspace normally. It's just that the entire screen is upside down (e.g., score/text and saucers), so it's a little odd, given that the controls move you in the expected direction.
Also, the sound works, but the volume is a little low, so you don't get the full rumble and crashing of the sound effects. But you actually get 80% of the gaming experience with zero modifications, which is kind of neat, though I found myself wanting after a while to have it be 100%.
Setting out to fix these issues, it turns out there are 3 main modifications that need to be done:
1) Flip the Y-axis of the video output, so the image displays properly off of the mirror.
2) Remap the control signals to the proper cab switches.
3) Modify the audio output amp to boost the volume.
These 3 modifications turn out to be pretty easy to do, and can be reversed if needed. We'll handle each one separately.
Mod 1: Flip the Y-axis of the video output.
Asteroids Deluxe and (some other vector boards) actually have control signals on the edge connectors that can flip the X and Y axes of the output video signal. This is mainly used for cocktail cabs, where the harnesses are designed so that these pins are configured differently in the cocktail harness, which the board can detect, and flip the image when needed in cocktail mode.
An Asteroids Deluxe PCB actually has separate edge connnector control pins for inverting the X and Y axes independently. However, Asteroids only has one pin, which flips BOTH the X and Y axes at the same time, therefore it alone cannot be used to accomplish what we need.
However these inverting mechanisms basically manipulate a pair of DC voltages (+8.2 and -8.2V) on the PCB, which are connected to pins on a couple of switch IC's in the video output section, for both the X and Y axis outputs. If you reverse these voltages for either axis' switch chip, that axis flips. For AD and some other vector boards, the axes can be controlled separately. However because for Asteroids these two controls are tied together, we must cut them and manually swap the voltages for just the Y axis, which will flip the screen the way we want.
There are multiple ways and places to do this on the board, but I believe the simplest is right where the two signals leave the X-axis switch, and head toward the Y-axis switch. This is the MC14016B chip at location D13, shown in the picture below. You can make two small cuts in the traces leading away from the chip (shown in red in the pic below), and solder small wires from each IC pin to the opposite trace (shown in blue). Doing this here is convenient, because there's room to access the traces, and if you ever want to undo the mod, you just remove the wires, and solder over the cuts with a tiny bit of solder, restoring the original traces.
After swapping these two lines, you should see properly displayed video in the mirrored display.
Mod 2: Remap the PCB control lines to the proper cab switches.
The second modification is to fix the mapping of the controls, by modifying the signal paths on the Asteroids board. It turns out this is very easy to do.
Each control signal comes into the PCB via the edge connector, via a separate pin. For Asteroids, each signal goes through an inductor before going into an LS251 mux IC, which connects to the data bus. The inductors are all aligned in a row on the PCB, near the edge connector. This is the easiest place to remap the signals to the desired places.
There are 3 pairs of signals that need to be swapped around. And it turns out (at least on my PCB), that they are all right next to each other, in the row of inductors. You will need to make the following swaps:
Swap the L5 and L6 signals (COINL and START2)
Swap the L7 and L8 signals (COINC and START1)
Swap the L9 and L10 signals (ROT LEFT and ROT RIGHT)
You can just desolder and lift one side of each pair of inductors, then move one inductor to the opposite hole, then you'll have to solder in a short piece of wire (e.g., a piece of lead wire from a resistor) to connect the other inductor to the opposite hole, as shown in the pic below, for the 3 pairs of signals.
After swapping the 3 pairs of signals, your controls should operate properly.
Mod 3: Modify the audio output amp to boost the volume.
The final modification involves modifying the audio amplifier circuit, to boost the volume of the audio signal that is sent to the AR board (where it is amplified further, to drive the speakers). You only have to do this if you are unsatisfied with the low volume that occurs by default, but it's super simple, and worth doing IMO, as the playing experience is much better at full volume, especially in the AD cab.
Note that this mod assumes you are using a stock Asteroids Deluxe AR-1 power supply board in the cab. Asteroids and AD used slightly different AR boards, where the Deluxe AR had modifications to support the higher output signal from the game PCB, and used different (larger) 3300uF coupling caps instead of 1000uF, which changed the low-frequency response. This mod basically changes one resistor on the Asteroids PCB amplifier circuit, to make it similar to the AD circuit, and more compatible with the AD AR. If you are using an Asteroids AR, you do not have to do this mod (however that defeats the purpose of having it be a plug-and-play PCB swap.)
If you compare the audio output amplifier sections between Asteroids and AD, they are very similar. The primary difference is the gain of the main stage. These circuits use LM324 op-amps, which in the configuration used on these boards, have a feedback resistor that determines the gain. If you look at R86 on the Asteroids circuit, it is 1K ohms, while the equivalent resistor in the AD circuit is 10K ohms. All you have to do is replace resistor R86 with a 10K, and the Asteroids board will output a stronger signal.
The resistor is right below the LM324 op-amp chip, at location P12. It is circled in the image below. Just replace it with a 10K, and your volume should be at full level in the AD cab.
Summary:
This writeup is actually longer than the actual procedures require, but I wanted to include additional detail, for those who are curious about the 'why' of what is being done, and also to aid people in cases where the boards may be slightly different than my Rev -06 PCB which I did this on (though I don't expect the sections of interest to be significantly different between revisions.) In the end however, the mods can be done pretty quickly, and Asteroids (in my opinion) looks pretty damn cool through the electric blue mirrored display of the AD cab.
Good luck modding your boards, and feel free to PM me or post here with any questions. Comments welcome.
Regards,
Andy



