My "custom" Supercharger modification

[shadow460]

What wears on the device's audio amp is having any signal fed to a grounded source. Sounds to me like it's feeding the same signal to both left and right channels, but when that signal goes through the right channel, it grounds the right channel. the left channel remains unaffected.

If you adjust the audio device's balance all the way to the left, you'll have nothing going to the right channel for it to ground out. Likewise if you wire the tip and that middle ring together and separate them from the ground.

[Mark Wolfe]

What wears on the device's audio amp is having any signal fed to a grounded source. Sounds to me like it's feeding the same signal to both left and right channels, but when that signal goes through the right channel, it grounds the right channel. the left channel remains unaffected.

If you adjust the audio device's balance all the way to the left, you'll have nothing going to the right channel for it to ground out. Likewise if you wire the tip and that middle ring together and separate them from the ground.

 

 

So, you're saying bridge ring and tip? Which would be the same effect as using a mono Y cable. I thought of that first but the ease of this method was too good to pass up and I doubt the wear on the audio amp will be very much since the amount of time audio is being played back is so minimal.

 

Changing the balance setting on the iPOD is a good tip though. no pun intended. I'll try that. I don't use this iPOD for anything else anyway, so i could just leave it that way.

[+chriswhit]

Oh, what the heck...here's a detailed description of how I did it:

 

Here I present The Complete Idiot's Guide to Modifying The Supercharger

 

First, we need to know which pin is #1 on each of the IC's, and how they other pins are numbered. I'm going to treat the row of components on the one side of the board as an IC for numbering purposes. I'm also going to explain a simple mod to the audio line to make it easier on modern music devices and I'm going to add everything on top of the board instead of the bottom. I'm also going to assume you either have actual Starpath tapes and a stereo tape recorder like I do or that you have the mp3 files on your digital player. I'm going to assume that you have a program such as playbin that can turn .bin files into audio the Supercharger can load, and I'm going to assume you have at least one Starpath game in mp3 format on your computer.

 

The parts:

One resistor, 5K to 20K at 1/4 watt should work.

Two switching diodes, 1N914 is common and is what I used.

The smallest SPDT switch you can find. It'll have two positions at the lever, and three pins.

About a foot each of three or four colors of wire, I used red, white, green, and black.

One 1/8 inch replacement stereo headphone jack.

Rosin core solder, probably about three feet if you use a lot.

Elmer's School Glue stick

 

Tools:

15 watt soldering iron, grounded if possible.

Desoldering tool (recommended, but not required)

Straight blade screwdriver

Xacto knife

Wire strippers

#1 point Phillips screwdriver

Hacksaw

Hair dryer

Multimeter (known as a Fluke hereafter)

 

Case mod:

 

Use the hair dryer to heat the Supercharger's main label up. Gently begin peeling at one corner, heating as necessary to loosen the glue. Alternately, you can cut through the label with the Phillips screwdriver, but this will scar your Supercharger's label. Once the screw is exposed, you can leave the label as is and remove the screw. Working from the connector end of the cart, gently pry the halves apart. The cart will hinge open on the end label, so be careful not to tear the end label in half.

Remove the board and the audio wire, then reassemble the cart without them. Tighten the screw. Look at the end label, and look down the sides. You'll see a hole for the audio wire. We want another hole on the other side for the toggle switch. The plastic is not too tough, so your #1 Phillips will cut right through it. Note that there is a split between the case halves where you need to make the hole, so you have to squeeze them together a bit while you cut the hole out.

 

Now let's get an overview of the board. Hold the board with the component side facing you and the edge connector pointed down. Four IC's should be on the left. The top is the ROM IC, or U1. The next three are RAM, and for this guide we're going to number them from the top down, U2, U3, and U4. The largest IC is the custom Arcadia chip, which we'll call U5. LAst is the row of components which we will fudge and refer to as U6. U7 would refer to the 7432 in a modified Supercharger, but that's not present or we wouldn't need this guide.

Time for more physical mods. Make a square cut on the top left side of the board. It should extend down almost all the way to U1's legs, and it should be about that same distance across from left to right. In other words, make it square using U1 as a guide. My Supercharger had no traces in that area, but check yours anyway and if they are there, cut around them.

Next, let's knock out the simple mod first--the audio line. Cut the audio wire as close to the plug as possible, then strip about half an inch off the conductors. Grab that stereo jack you have and hook the white wire to BOTH of the connections inside the jack. The other wire is ground, so solder it to the largest connector. Make sure the ground and the other wires don't touch, then use the Fluke to ensure that the ground wire has continuity from the SC board all the way to the largest ring on the jack. The white wire should have continuity from the SC board to BOTH the middle ring and the jack's tip. If so, assemble the jack and that's done.

Another solution to this is to permanently mount a 1/8 inch mono male to 1/8 inch stereo female adapter onto the existing jack. That's what I did, then I taped the jack on with electrical tape and glued that down so it would not unwind.

 

Why mod the audio line anyway, you ask? Simple. Back in the day, shoebox recorders were common. That's whaty ou see pictured in the Arcadia manuals with the Atari--a shoebox recorder. Those old recorders have a monaural output.

On the other hand, today's portable CD players, tape players, ipods, mp3 players, etc, have a stereo output. The Supercharger was not designed to be used with these new devices, and plugging it into them results in the left channel only being fed into the supercharger, while the right channel is shorted to ground. This can strain the audio circuit inside your player (or whatever it's hooked to), resulting in premature failure of the right channel audio. I'm not saying it will damage your ipod or whatever, just that it could. It can also cause problems when loading games into the supercharger, as essentially only half of the signal gets through from the ipod (remember that an old shoebox recorder is going to route the whole signal to only one channel, the ipod routes it to two).

 

Now for the more fun mod:

 

A few posts up, Batari has a simple diagram which is the actual bankswitching mod itself. In his diagram is an OR gate. If you look at the pinout of a 7432, you see that each of the OR gates on that IC has two inputs, Ax and Bx, and one output, Yx. Let's consider just the first gate, then, which has inputs A1 and B1, and output Y1. The 7432 has a ground leg, which we will also recreate, and a power leg which we do not need.

Take your two diodes and note which end has the stripe. If you set the fluke to the diode check you can hook the diode up so that the black fluke lead is hooked to the striped end lead on the diode, and the red lead to the other end. You'll see some numbers on the fluke. If you hook the fluke leads up the other way, it will show an OL or some other odd message instead of numbers. This tells you which lead on the diode is anode--when the numbers show, the red fluke lead is on the anode. The striped end of the diode is cathode, and that's where the black fluke lead would be when you have numbers on the LCD screen.

take the two diodes and twist their cathode leads together. The resistor does not have anode and cathode, so just pick a lead and warp it around the cathode leads. Leave about 1/4 inch of the resistor lead untwisted. Solder the whole thing together save for that last 1/4 inch. Trim the diode leads but leave the resistor lead alone.

 

Now look again at the SC board. Each of the IC's has a notch EXCEPT for U6 (that's the component bank). With the notch pointed UP, the top left pin is pin 1. The pins are numbered down the left side, then back up the right side. The memory chips U1 to U4 all have 24 pins, so the top right pin is pin 24. On the left side, ging from notched end to other end you have pin 1 to pin 12, then going from other end to notched end you have pin 13 to 24. REMEMBER THIS. As for the component bank at U6, we're going to assume U6 is oriented the same way as the custom IC, U5.

 

Hook one of the anode leads from your OR gate (that's the diodes and resistor circuit you made) to pin 7 on U4. It's the seventh pin down on the left of the chip. Flip the board over and cut the trace on THAT side of the board that leads from pin 7 of U4 to pin 35 of U5. pin 35 is sixth up from the bottom on the left side of U5 as you held the board earlier. Check it for yourself and see, though.

See that conglomerate of wires with the cathode leads? Tin the 1/4 inch lead that you left on the resistor, then solder it to pin 35 on U5. Ensure that the three leads you soldered together are still, in fact, together.

Next, solder the other lead of the resistor to pin 12 on U3. This is where the ground connection from batari's diagram is made on the SC board.

Cut the other anode lead to a length of about half an inch. Position the OR gate above U3. You're done with the board for now.

 

Now take the switch and hook about six inches of three colored wires to it. I hooked red to the center lead, then I flipped the switch body so it's perpendicular to the board. I hooked black to the top lead and green to the bottom.

While you're at it, let's prepare the switch to be mounted in the SC case. It should have a large flat washer and a smaller star washer. Remove all the hardware from the switch body, then place the flat washer on followed by the star washer and one of the nuts. Leave the nut loose until you have the wires connected to the switch.

Once the wires are connected, lay the switch and the SC board back into the case. Cut the red wire so that its long enough to solder to the remaining anode. Strip and solder it there.

Cut the green wire so that it can reach pin 13 of the component bank at U6. You can sloder to the component's lead if you wish. Strip and solder.

Cut the black wire long enough to reach pin 27 of U5. Once again, strip and solder.

 

Now for the testing:

 

With all of that done, you're ready to test the mods. Plug in the Supercharger, then connect the fluke leads on either side of the resistor so that the black lead is hooked near U3 and the red near U5. Set the fluke to measure DC volts, then hit the Atari's power. You do not need to set DevOS to play a 2600 game, just hit the power. (If you don't know what DevOS is, then you don't have to worry about this.)

The Supercharger will power up. If the screen is normal, then everything is good so far. Check the voltage on the fluke. If it's between 0 and 2.5, then you're good. If the screen is NOT normal, then the voltage you're measuring is probably too high. Take another 20K resistor from the pack and solder it in parallel to the first one. I literally mean that, solder them so that it looks like current should flow through BOTH resistors (because if you do this right, it will). Try it again. The voltage should be lower this time, too.

 

Now let's hook the SC to your sound source. You know the drill, set volume and tone controls to max, then play the file. MAKE SURE to reset them when you are done!

Flip the switch so that its lever is toward the component side of the SC board. You should be able to load a Starpath game into the supercharger and play it normally. If it crashes at any point, flip the switch and try again. I used Escape From the Mindmaster. It will crash just after the title screen if the switch is wrong. If that happens, flip the switch back and try again. The Starpath game should load and play correctly.

Now flip the switch to the opposite position from the one that you played your Starpath game in. Use playbin to load Atari's release of Pac-Man into the Supercharger. Yup, non a non Starpath game just made its way into your supercharger! If the switch is in the correct position, Pac-Man will play normally (and it will still suck). If the switch is wrong, Pac-Man will crash as soon as you try to start a game.

 

If it passes all the tests, then you're ready to reassemble the SC. Ensure that the switch, the audio wire, and the SC board are in the lower part of the case correctly, then carefully close up the SC like a book. Tighten down the nut on the switch, then replace the screw. If you peeled the label off, cover the entire area with the stick glue and press the label back into place. If not, you might throw some paint on the screw head to make it match a little better. Mine's still silver.

 

That's it! thanks to Bob Colbert, batari, Chad Schell (for his work with the Cuttle Cart and getting the audio files into both it and the supercharger) and anyone else who's worked with the supercharger to make this mod possible.

I used this method of modding my supercharger and It works great with no glitches. used a 5k resister. great mod. thanks

[shadow460]

5K might be the best value to use. Depends on how well it runs with that 7800, though. Your 7800 and mine are different revisions.

Mine runs OK with the resistor value at 20K.