Amiga A3640 CPU Board Repair

Although surface mount capacitors were used on the board, it is easier as a field repair to use thru-hole radial leaded capacitors. Those supplied in the kit are rated at 35 Volts and made by Panasonic.

Five capacitors are included in the kit. Three of them have their leads bent such that they lie parallel with the PC Board when installed. Look at these closely and you will see that one is bent 180 degrees opposite the other two. This one is meant to replace C105. The other two are meant to replace C106 and C107. (See Figure 4.) The two remaining capacitors are meant to stand straight up and replace C102B and C102E, if you choose to replace these. (See Figure 5.)

When installing the capacitors, you need to be aware of their polarities and install them correctly in order to not repeat the problem that you are correcting.

This means that C102B and C102E are installed per the polarity markings on the silkscreen of the P.C. Board. C105, C106, and C107, however, need to be installed with their polarities opposite the silkscreen markings. We will put the positive lead of the capacitor to the minus pad and the negative lead to the plus pad.

With a very low-heat soldering iron (about 23-watts), apply a small amount of solder to each of the capacitor leads, as they sit on the surface mount pads. It is important to make the solder connection as quickly as possible, since we are soldering to a surface mount pad. This pad is just sitting on the surface of the printed circuit board. Any excessive heat will stress the pad beyond its' limits and it will lift off the board, causing a different sort of problem that we really don't want.

Another thing to remember is to not bend the capacitor's leads after it has been soldered to the board. This would apply undue stress to the pads which may cause them to lift off the board.