Replacing Capacitors

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Warning Identify a low temperature that your solder consistently melts at by referencing your solder's datasheet to avoid overheating solder pads/vias and increasing risk of ripping pads.

Electrolytic capacitors are the most common component in need of replacing in electronics. All electrolytic capacitors have a specified lifespan in their datasheet. Generally, most capacitors start to fail after ~20 years as they are prone to leaking or drying out over the span of decades. The Capacitor Plague also accounts for massive failures of popular capacitors made between 1999 and 2007. This page is a reference for how to remove and install new capacitors. In some cases, you may wish to replace undamaged capacitors with ones of a different value for specific effects (such as replacing a ceramic filtering capacitor with a different rated one to eliminate noise).

If you did not buy an existing kit of capacitors made for a specific device, you might consider Building a Capacitor Kit and sharing it (after verifying functionality).

Identifying Bad Capacitors

As mentioned before, all electrolytic capacitors have a stated lifespan and will fail eventually. Often times — but not always — when capacitors fail, it is visibly apparent. The top of the capacitor bulges instead of being flat or it burst and leaked. The most problematic issue is if the capacitor leaks underneath itself onto the the motherboard, which can cause shorts, corrode pins on chips, or — depending on the composition of the fluid — it can eat through the motherboard and damage traces. Due to its liquid nature, the fluid can also flow through holes in the board or vias and affect components on the other side of the board and the vias themselves.

However, capacitors can silently fail with no visible issues. In order to fully test them, you will need a capacitor tester and to remove the capacitor from the circuit. With the low cost of capacitors, it is often a better idea to just replace the capacitor if it's suspected to be failed.

Well-Known Bad Capacitors

  • Xbox Clock Capacitor (causes multiple issues)
  • Most Game Gear and model 1 Sega CDs need a full recap at this point (audio/video issues)
  • TurboDuo / PC Engine Duo capacitors generally corrode nearby components or traces (power, disc loading or audio issues)
  • TurboExpress / PC Engine GT and PC Engine LT always need recaps and nearby components can be damaged
  • Amiga 600 and 1200 computers require full recaps due to leaky SMD capacitors
  • Multiple 30+-year-old computer power supplies
  • NES AV/power modules (especially the large 2200 uF filter capacitor)
  • Fujitsu FM-7 computers also tend to have leaky capacitors on the motherboard

Highly Recommended for capacitor replacement

Although not mandatory it is well accepted within the community and recommended at this point to recap the following:

  • Dreamcast PSU
  • Saturn PSU
  • PAL 3DO FZ-1 units
  • PS1 PSU and also the 220 uF capacitors filtering the luma and chroma signals
  • PAL SNES
  • Early revision (VA0-VA4) Sega Genesis and Mega Drive consoles, especially those manufactured in Taiwan
  • FMT Marty PSU and audio filtering capacitor
  • N64 PSU
  • Any PCE CD hardware

Capacitor Removal

The method you use to remove capacitors depends on the type of capacitor and how it is installed. Note that there are products such as Chip Quik solder paste which reduces the melting point of the solder on board, thus keeping solder liquid for a longer period of time, allowing for easier removal of capacitors.

Through-Hole Electrolytic Capacitors

  • If the through-hole capacitor is not flush to the board and you can see the legs underneath:
    • Use flush cutters to snip each leg to remove the can. From there, you can remove each leg by holding it with tweezers then heating the solder hole and lifting the leg out. Ensure that you wait until the solder is completely liquid before lifting the leg out to avoid accidentally pulling metal out with it.
  • If the through-hole capacitor sits flush to the board:
    • Position the board in a way that you can access both the top and bottom of the board. Heat one solder hole completely and gently lean the capacitor to lift the leg a small bit. Repeat the process, alternating legs until it is completely removed.

Electrolytic Surface Mount Capacitors

Surface mount capacitor removal runs a higher risk of ripping a solder pad off of the motherboard. They consist of the radial can, a plastic base that the can sits on, and leads that go through the plastic base and connect to the surface of the motherboard.

Warning Identify a low temperature that your solder consistently melts at by referencing your solder's datasheet to avoid overheating solder pads/vias and increasing risk of ripping pads.
Warning While some recommend heating and lifting one side at a time, this is NOT recommended as it has a high risk of ripping a pad off of the board. See the troubleshooting section if a pad is ripped.

There are two popular methods to remove these capacitors:

  • Heating each lead of the capacitor until the solder is liquified and lift the capacitor off of the board. You will likely need to use Chip Quik or soldering tweezers to be able to keep both leads liquified simultaneously. This runs the risk of solder solidifying before lifting the board, resulting in a pad being ripped off the board. Generally, you would not apply any force in the lifting action, but often times if a capacitor has leaked, the capacitor will be stuck on the board due to the fluid dying underneath.
  • The "push and twist" method is a controversial method. This involves using pliers to grab the capacitor can, pushing gently downwards, and rotating the capacitor in a complete circle until the leads break off against the plastic base. From there, you can snip any remnants of leads above the plastic base, and the base will lift away using zero force. The very bottom of the leads will still be attached to the motherboard and will require you to heat and lift them away with tweezers.

Ceramic Surface Mount Capacitors

Generally, there are two methods to removing ceramic surface mount capacitors:

  • With a soldering iron. Either use Chip Quik to heat liquify both pads and knock the capacitor away with the iron or lift it away with tweezers. Alternatively, you can add a bunch of solder to one side and blob the solder over to the other pad, effectively liquifying both sides at the same time so that the capacitor can be removed.
  • With hot air. See the Replacing ICs page for tips on hot air rework.

Cleaning the Area

If a capacitor has leaked, generally it will look like a very faint dark stain on the board. If it was wicked up by dust, it may look different in appearance to dust in other areas on the board. To clean this, liberally wipe the area using a cotton swab and 90% or higher isopropyl alcohol or vinegar. Visibly inspect to make sure that nearby components — and components on the other side of the board if there are open holes or vias in the board that it could have flowed through — are not damaged.

Capacitor Installation

Ensure that you have cleaned the area thoroughly before installing new capacitors. Ensure that the pads or holes that you are attaching the new capacitors to are clean looking and have an appropriate amount of solder on them.

Through-Hole Electrolytic Capacitors

  1. If the leads of the capacitor are not straight, gently bend them to be straight.
  2. Check the orientation of the positive and negative holes on the board and insert the capacitor aligning the negative hole with the negative lead, and the positive hole with the positive lead.
  3. If the capacitor will not insert all the way flush to the board, remove it and use tweezers to bend the leg once or twice to get it to fit and sit nearly flush. Avoid bending the leads up inside the can.
  4. With the capacitor inserted, heat the solder hole and lead at the same time on the opposite side, and add solder to it. Repeat for the other lead.
  5. Trim the leads so that they do not short on anything else. If possible hold or shield the leads with your hand so that there's no possibility of it being shot into your eyes.

Electrolytic Surface Mount Capacitors

  1. If you have solder paste, add some to the solder pad.
  2. Check the orientation of the positive and negative holes on the board and place the capacitor on the board, aligning the negative pad with the negative lead, and the positive pad with the positive lead.
  3. Holding the capacitor in place with one finger, touch your tinned soldering iron to the lead and the pad at the same time to make the connection.

Ceramic Surface Mount Capacitors

Ceramic surface mount capacitors are non-polarized, meaning that they can be installed in either orientation. Simply hold the capacitor in place with tweezers, solder one side and wait for it to cool before letting go of the capacitor and soldering the other side. Using flux is highly recommend as it will help the solder flow to the pads.

Troubleshooting

If you ripped a solder pad off of the board. Check if it is still connected to the trace on one side.

  • If it is, you can put a very tiny drop of super glue underneath the pad and glue it down in place.
  • If it is not connected to the trace, visually follow the trace to the nearest pad, connected component, or via and solder a wire between that point and the lead of the capacitor.