Capacitor Replacement

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Small electrolytic capacitors in all old Macs, probably up until the mid 1990s, have begun to leak. We guarantee it. Without fixing this problem, your Mac unfortunately won't live long, and in fact many have probably already died. But fear not! Even a dead Mac can be brought back to life by replacing its small electrolytic capacitors.


The first thing you have to do is open your Mac and remove the logic board. If you are unsure how to do this, search with Google to find some good directions, so you don't break something in your precious artifact of a Macintosh.

Next you want to inspect the board. Hold it up to a light source so you can see the light reflecting off of the board. Now focus on the areas around the small silver cylinders sticking up out of the board (the electrolytic caps). You will notice that the board isn't as shiny around these capacitors. This is some electrolyte that used to be inside of the capacitor. It has leaked out somewhat.

Promptly purchase a set of replacement capacitors, preferably in "tantalum" form. These are solid and will not ever leak. Forum member trag (Jeff Walther) is offering such sets for sale in the forum. (go there)

Here are some instructions, quoted from Jeff:

In my experience, the easiest way to remove the old caps is to use two soldering pencils at one time. That way you do not put mechanical stress on the circuit board (as you do when you heat one side at a time). A grounded 15 watt soldering pencil is available from Radio Shack for under $10. So, if you already have one soldering pencil, go pick up a second one and make this job easy for yourself.

If you try to use just one pencil, by the time you can heat the second pad, the first will have cooled. With the one-pencil-method you are forced to either get the entire cap and board so hot that the solder will stay melted while you move the pencil from side to side, or you end up bending the cold solder on one side, while lifting the other side. That over-heating and/or bending is what typically leads to lifted pads on the circuit board.

With the two pencil method, you just apply a pencil to each end of the cap to be removed and wait until you can gently lift the cap with little to no resistance. It's useful to have a damp sponge on hand, as sometimes the cap sticks to one pencil tip or the other and it can be wiped off on the sponge.

Be sure to practice on garbage circuit boards if you are unsure of your soldering skills.

Before soldering on your new caps, be very sure to thoroughly clean the board. Many people have put the logic board into the dishwasher and run it without detergent. This seems to work particularly well. Taking it to the sink or tub of water with a toothbrush has also proven to be a good way to do it. Several days later, when the logic board is thoroughly dry, it's time to solder on your new capacitors. Practice on garbage boards if you are unsure of yourself. When soldering new caps back on, pay special attention to the polarity of the capacitor and the markings on the logic board. Often there will be a positive (+) symbol printed on the board. The side of the tantalum capacitor that has a stripe is negative (-), so face that side of the capacitor away from the (+) symbol.

Quantities of Capacitors in Macintosh Models

Some different revisions of logic boards may have different numbers of caps, so make sure to look first and verify this information. If yours is different, please create an account here and add it to the page by clicking the edit button up on top. Note that these numbers include capacitors only on the logic board and not, for example, in the power supply. Post on the 68kMLA forum if you suspect you have bad caps in your power supply and would like help.

Also note that when replacing your capacitors, it is okay to exceed the voltage rating of the old capacitors. You must not go lower than the original voltage rating, but exceeding it will generally make no difference. Using a capacitor with a higher voltage rating tends to extend the life of the new capacitor, but going TOO high can alter the characteristics a bit. It's best to exceed the original voltage by just a step or two if you desire.

  • Macintosh SE/30:

Replace with Tantalum:

10x 47µF (?)V

1x 1µF (?)V

Replace with Electrolytic:

1x 220µF (?)V

1x 470µF (?)V

  • Macintosh IIci 820-0242-A:

Replace with Tantalum:

8x 47µF 16V

2x 10µF 16V

Replace with Electrolytic:

3x 470µF 16V

1x 220µF 16V

  • Macintosh IIci (another revision):

Replace with Tantalum:

11x 47µF (?)V

2x 10µF (?)V

Replace with Electrolytic:

3x 470µF (?)V

1x 220µF (?)V

  • Macintosh IIsi:

Replace with Tantalum:

11x 47µF 16V

Replace with Electrolytic:

2x 220µF 16V

  • Macintosh Classic II:

Replace with Tantalum:

3x 47µF (?)V

2x 1µF (?)V

8 to 11x 10µF (?)V

  • Performa 450 (Macintosh LC III):

Replace with Tantalum:

5x 47µF 16V

5x 10µF 16V

1x 100µF 6.3V