VMU Power Supply Mod

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Revision as of 20:57, 18 June 2013 by ITEM-3 (talk | contribs) (Step 2 - Solder the wires)
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THIS IS A WORK IN PROGRESS

The VMU for the Sega Dreamcast can be modified to accept as a power source an alternative to the pair of CR2032 batteries the VMU is designed for such as AA batteries or an AC adapter that supplies 6V of direct current. The new power source can be soldered directly to the VMU, or a common connector can be soldered to the VMU to enable you to detach the new power supply.

Basically all we'll be doing is soldering the positive and negative ends of our new power source to the corresponding terminals of the VMU. Now, there are two ways to go about this: one is invasive and involves drilling and soldering directly to the VMU's board, and the other involves soldering directly to the battery terminals, which doesn't even require you to open the VMU. The former method will result in a better looking VMU, but the latter is easier, less risky, and entirely reversible. This guide will cover the second, easier method.

Tools needed:

  • Small phllips head screwdriver
  • Soldering iron
  • 6VDC power source
  • Voltmeter (optional but recommended for troubleshooting)

Step 1 - Selecting a Power Source

Batteries

Standard alkaline batteries (AA, AAA, C, D, etc.) can be used to power the VMU if 4 of them are used together. Since each alkaline battery generates 1.5V, putting 4 in series will generate 4*1.5V = 6V of DC current. It would be easiest to do this mod for AA or AAA batteries since it is not dificult to obtain an enclosure which holds 4 of one of those types.

Rechareable Ni-MH AA or AAA batteries may not be able to power a VMU unless 5 are used in series since a typical rechargeable battery only generates 1.2V. This information needs to be verified.

AC Adapter

For this AC adapter, the outside part of the connector is negative and the inside is positive.

You may be able to power your VMU using a generic AC adapter if it meets the following criteria:

  • It must output 6V of direct current (DC)
  • It should be capable of outputing up to at least ~340mA of current  It may require less current than that, but that is the lowest amount I've been able to experiment with.

If you choose to use an AC adapter, pay attention to the polarity of the cord. It's usually indicated on the front of the AC adapter, but if not you can use a voltmeter to determine the polarity.

Detachable cable (HIGHLY RECOMMENDED!)

An extension cord for an AC adapter

To do this mod right, you should attempt to track down a cord similar to the one pictured to the side. What it is is an extension cord that takes a cylindrical AC adapter's cord and splits it into two wires. What this cord will enable you to do is solder the female end to the VMU and use the male ends to modify a battery pack or AC adapter (if necessary) so they can plug into the female end. This will allow you to detach your new power supply from the VMU when you're not using it and to switch between AC power and battery power as you please.

If you decide to use an AC adapter with this cord, you should first identify its polarity (see above) and then use a voltmeter on the extension cord to figure out which wire corresponds to which part of the plug. This is so that when you solder the female end to the VMU you will not mix up positive and negative. If you're only using a battery pack, you can choose your polarity; just make sure you're consistent with both the female end (VMU side) and male end (battery side).

Step 2 - Solder the wires

Once you've decided on a power supply and you've identified which end of it is positive and which is ground, it's time solder. Flip over the VMU and remove the battery cover and the two CR2032 batteries to expose the battery terminals. The large blade on the bottom is the negative end and the small blade off to the side is the positive end (see pictures below).

All you need to do is solder the wires of your power supply to the correct terminals of the VMU. If you're going to directly attach the supply to the VMU, make sure you give yourself plenty of cord length. If you use an extension cord to create a detachable plug, make it just long enough so that the thick end of the cord won't interfere with plugging the VMU into the first slot of a controller with something else in the second slot. With this mod, you will not be able to attach the VMU to the second slot any longer.