Xbox:Clock Capacitor

The clock capacitor is a small capacitor which allows the Xbox to keep track of time while unplugged. The clock capacitor on models 1.0-1.5 (and their debug unit counterparts) is of low quality and prone to leaking a strongly basic fluid after about ten years from manufacture. While the leaking may not cause any immediate damage, it will eventually eat through the motherboard and cause permanent damage to nearby traces, resulting in the Xbox being unusable. In some extreme cases, they can catch fire, though this is rare. This guide will assist you in removing the clock capacitor and cleaning up any spilled fluid.


 * If you are running an old BIOS or softmod (essentially from before 2004), you will need to update your softmod or modchip BIOS to a clock loop patched version before proceeding, or else you will get stuck in a clock loop. Unmodified Xboxes on the stock MS Dashboard will not get stuck in a clock loop.
 * Motherboard revision 1.6 corrected this issue with a higher quality capacitor, and therefore removing the cap is unnecessary and will result in the Xbox giving an error due to revision 1.6 requiring a working clock capacitor. You can check your motherboard revision on this page.
 * This is possible, though unnecessary, to replace the clock capacitor with another 1F 2.5V capacitor. However, the only benefit to be gained from this is that your Xbox will keep time for ~3 hours after being unplugged. However, some dashboards have a feature that will auto-set the system clock via the Internet anyway, negating this benefit Do not replace the capacitor with the exact same model, as it will be prone to leak again. Be sure to line up the white stripe on the new capacitor with the filled in part of the circle printed on the motherboard where the capacitor goes; installing it backwards could potentially cause a fire or other catastrophic failure.

A video demonstration of how to remove your clock capacitor can be found on MrMario2011’s channel.

Removing the Capacitor

 * 1) Identify the clock capacitor. It sits near the front left of the motherboard behind the first player controller port, underneath the CD/DVD drive. It is a medium sized capacitor that looks like this for 1.0/1.1 motherboards or like this for 1.2-1.5 motherboards. On a small amount of 1.4 motherboards, it may be a gold colored capacitor, identical to the one on 1.6/1.6b motherboards. It is recommended to remove it from 1.4 motherboards as it is unnecessary, but do not remove it from a 1.6/1.6b motherboard.
 * 2) Remove the capacitor by wiggling it until it is loose and then gently pulling it off with pliers or by hand.
 * 3) Check for any fluid leakage. It may look white and powdery like this. If you see any fluid, follow the below steps to clean it. It’s still recommended to clean the area in case it’s a very small amount that you can’t see.

Cleaning up Fluid
Dip a Q-tip in isopropyl alcohol (IPA, rubbing alcohol) and rub any area where it looks like there may potentially be fluid. The IPA will neutralize the fluid and prevent the motherboard from corroding any further in the affected area. If there are large amounts of corrosion or fluid, you can use a toothbrush to gently scrub the area. Let it dry completely before powering on.

Repairing a Damaged Trace
If the clock capacitor fluid had eaten through a circuit trace, you can attempt to repair it with a sharp knife (such as an X-ACTO knife) and a circuit trace pen or small piece of wire. A window defogger repair kit also is a cheap alternative to a circuit trace pen.


 * 1) Use the knife to scrape off the surface above the damaged area of the trace, including a little bit extra on either side to expose a bit of undamaged copper. Cut out the damaged area. You may need to do the same to the other side if it will not come out.
 * 2) Clean the area using isopropyl alcohol and a Q-tip. Make sure to clean the undamaged copper areas well to make sure they aren’t covered in silicon dust.
 * If using a circuit trace pen, fill the gap between the undamaged copper areas and cover some of the undamaged copper on both ends. Allow it to dry as directed in its instructions.


 * If using wire, make sure that it is close to the same width as the trace, then cut it to the size of the missing trace or slightly smaller, place it in the hole, and smooth some solder over each end, connecting the undamaged copper to your new wire. It may help to apply flux to the wire and copper first, and hold the new wire in place with a small piece of electrical tape.
 * (optional) Apply epoxy, hot glue, or electrical tape over the new trace to protect it from the elements.

Background and Technical Information
The clock capacitor is a 2.5V 1F supercapacitor, that is, a capacitor that can hold a large amount of charge and that can act as a replacement for a battery in some situations. It uses aerogel for an electrode which is different from a dielectric, as supercapacitors are constructed differently).

Bunnie Huang did some analysis of the clock capacitor system at one point, which can be read in full here. Bunnie speculates that the rationale behind choosing a 2.5V clock capacitor instead of a more standard 3V coin cell battery, was because the clock component was located on the MCPX, and the fabrication process of that chip made a 3V power source for the clock impossible, resulting in a barely workable compromise. Bunnie also suggests that the current draw required by the MCPX is high and thus drains the capacitor quickly, within about 3 hours after being unplugged, which was confirmed by other users. He concludes:

So in the end, the answer is: MSFT cut cost by not putting a long-life real time clock part on the XBOX, and instead integrated it into the MCPX; because of this, the current draw was high and they were forced to use a supercap which charges while powered on, because if they didn't by the time the box was shipped to the customer, the battery would be mostly dead. Bunnie also determined that the clock will turn off and stop drawing current if the capacitor is drained or disconnected, because the clock now has now lost its reference point for keeping time, and there would be no purpose to turning it back on until the console next boots.