How To: Modify an Asteroids PCB for use in a Deluxe cab

andrewb

Well-known member
Joined
May 14, 2014
Messages
28,987
Reaction score
16,967
Location
Portsmouth, New Hampshire
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.


r0s3kFg.jpg



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.


hrMoTOH.jpg



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.


Uc6U21o.jpg



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
 
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.
there are 3 main modifications that need to be done:
Mod 1: Flip the Y-axis of the video output.
Mod 2: Remap the PCB control lines to the proper cab switches.
Mod 3: Modify the audio output amp to boost the volume.
Summary:
Asteroids looks pretty damn cool through the electric blue mirrored display of the AD cab.
Andy

Andy, a sincere (THANK YOU * 1000) for an excellent, simple, easy to follow, description with great on subject pictures. I have always liked the 3D mirroring type effect of the AD cab over an A cab. But I like the game play of A much better than AD.

I had someone modify my A PCB years ago. I don't know what they did, but it works fine, so they may not have done it the way you did, but in the end it works great. As you said, there are different ways and places to accomplish what you specify, but I sure like the way you made it undertstandable and simple.

Only thing I'd like to mention in case someone missed it, this is for playing Asteroids in a stock Asteroids Deluxe full size upright cabinet. Mod 1 (flip Y) is NOT needed for the cocktail or cabaret. Mod 2 (controls) & 3 (audio) would still be needed for cocktail and cabaret.

Great work, great job. Thanks so much for documenting it.
 
This is the best post I've seen here in weeks. Very nicely laid out, and informative. As an AD owner, I'd LOVE to give this a try in my cabinet.

Thanks so much for the great info! Rep to you!
 
This is so helpful! I spent a week trying to put together this info and it was not easy to find.

I wound up making an adapter like this one to correct for the AD harness differences: http://www.brasington.org/arcade/tech/astdlx/

I came to the same conclusion you did about how to flip the game after reading this old vectorlist post: http://www.vectorlist.org/Vectorlist/2002/04/0000.html

What I could not find anywhere was specific info on fixing the audio level problem. So thanks very much for posting this. I can't wait to make this mod. [Note: I checked the manual. All of these are 1/4 watt resistors.]

Now all that's missing is a switcher so I can flip from AD to Asteroids with the push of a button.
 
Last edited:
It works great!

Limited time today because it's Valentine's day but I had the AD harness already made so my controls were already working properly.

Changing out R86 with a 10k ohm resistor worked perfectly. I now have full sound volume.

Swapping the lines at D13 was tricky. I wound up pulling up a bit of the trace and had to solder in further down on one side. Anyway, I checked continuity and the lines checked out fine.

When I power it up I had to adjust the size a bit but now I've got Asteroids working perfectly on my AD cabinet!

Anyway, thanks again to the OP for the excellent post.
 

Attachments

  • Asteroids in AD.JPG
    Asteroids in AD.JPG
    160.5 KB · Views: 83
Last edited:
Nice work, CaptainHendry!

(And thank you to all for the nice comments. I appreciate it.)


Regarding the soldering on the Y-flip mod, a couple of things that might help:

The best thing to use to cut the traces is a sharp exacto knife. You might pull the trace off if you try to use something with a wider blade, like a utility knife. The cuts don't have to be very wide, and the exacto knife is thin enough that it might even be hard to see that there's a cut, but if you make the cut cleanly, it will be good enough such that you can check it with a DMM and not get continuity.

Also, I originally suggested soldering wires on the component side of the board, at chip D13. I do this because I like to keep the mods on my boards as tight and small as possible (to prevent them from being damaged or ripped off accidentally), however one could also equally argue that you should make them conspicuous, so others in the future can see that the board has clearly been modded.

Also, I have a very fine-tipped soldering iron, so I had no problem soldering a thin wire onto the traces on the component side. However if you have a fatter-tipped iron, this might be a bit more difficult, in which case you can still cut the traces on the component side, but solder the wires on the solder side, to the following pins:

1 wire from D13 pin 12 to B13 pin 13
1 wire from D13 pin 13 to B13 pin 12

Note that the D13/B13 chip locations above are for a Rev-05 or -06 board, and for an -01 through -04, it should be D12/B12, respectively.

Hope this helps.
 
Thanks. I have a Weller iron with a fairly small tip so I was able to get a wire soldered to the trace but when I bent it to attach to the IC pin (pin 13 in this case) the trace lifted off the board. The wire was pretty thin (maybe 24 gauge) so there wasn't a lot of torque happening but it lifted right up to the socket for the next chip. I didn't want to leave it hanging off the board like that so I cut it and soldered in a bit farther down with a longer piece of wire. No problem with it the 2nd time.

Thanks again for the tips and photos. Since the AD multi-game kit isn't really available this seems like the best option for people who already have an AD and want to add Asteroids in the same cab.

Now if we could just work out that switcher.
 
So technically, can you now put in a switcher create jamma adapters for both pcbs, and have a multi-asteroids?


This is an interesting question.

I think the short answer is 'not exactly, but maybe', as it's a little more involved than that. However, I think it could be done, and would be a very cool project, which I actually want to try.

I personally don't have any experience with JAMMA switchers, but I've read up a little on them, and from what I understand, you plug a power supply into them, and they power both boards simultaneously, while switching the control and video lines between boards, either with a dedicated button/switch, or by pressing the P1+P2 buttons simultaneously.

This scheme makes sense given JAMMA PCBs and a switching PS. However in Asteroids, you have the AR board instead of a switching PS. The AR board also handles the sound amplification for the speakers, so there's that too, but I don't think that's really an issue.

Most modern PCBs are low enough power, and the new switching PS'es are high enough power (relatively), that you can power two boards with one PS. However for the AR's, this isn't as certain.

I know from measurements that an Asteroids board draws around 2.2-2.4 amps on the 5V line during normal operation. This means to power two of them, you're looking at 4.5-5A draw from the AR-1. Can it do this? Maybe. I know that Battlezone PCBs draw around 4.5A from one AR-2, which has basically the same 5V supply circuit as the AR-1 *I think*. I'd have to go back and doublecheck that, though.

So, if you could power two boards simultaneously, I'm thinking you could likely mod a JAMMA switcher to do it. Otherwise, you need a scheme to switch power between boards too, and you'd want to do that while power is off, as you don't want to switch a 2.2A line between two PCBs while they're running, with the types of low-power relays I believe they use on those JAMMA switchers.

If anyone has any recommendations and/or info (pros/cons) about the different JAMMA switchers out there, I'd be interested to hear, and pick one up to do some experimenting, as I agree that a multi A/AD cab would be pretty cool.
 
I asked Mike at Mike's Arcade about the possibility of using his switcher and he said he wasn't sure it would work but that he'd think about it.

A lot of these switchers seem to power both boards at once which has advantages but, as you note, also creates a problem if you're running a stock power supply. I was actually thinking of bypassing the problem by using a switcher to divert power to one board or the other. There are only two power lines going to these boards, a +5V and a 36VAC.

I found a board on ebay that seems like it could handle switching both the +5V and the 36VAC separately using a latching relay that can be triggered by a single momentary switch. The board also runs on 5V so it could be powered by the AR and since it's latching there's no major current draw and the switch stays wherever it is when you turn it off (so if you were playing AD, AD would come up the next time you power it on): http://www.ebay.com/itm/Panel-Mount...l-Latching-DPDT-Relay-Module-5V-/371445006779

I was thinking you could just run a static splitter for the control lines but (at a minimum) the X, Y, Z outputs would need diodes to prevent them sending power to the deselected board. I don't know. Maybe every line would need a diode but diodes are cheap.

Powering one board at a time is a lot better than pulling the game out, taking off the rear door and physically moving the harness. I could live with the few seconds it takes to boot up each board.

What do you think?

Edit: Also, are you sure about the power draw? Figures I had seen for AD were a lot lower: http://forum.arcadecontrols.com/index.php?topic=115882.0
 
Last edited:
Bumping an oldie but goodie, for any newer folks who may never have seen it.

I can't believe this was four freaking years ago. Time flies, man.
 
thanks for this posting, did the inductor mod to an Asteroids board today so I can play it in my ast dlx cabaret - it works great! swapped the AR board so didn't need to perform the audio mod or the flip the video since there's no mirror :)
 
Back
Top Bottom