Capacitor replacement - Caught just in time

[Bryce]

Hi all,


not CPC related, but I thought I'd post this here anyway as many of you probably own an Amiga too. One of the users here sent me an A1200 PCB that is having video issues. Literally in the knick of time, another month and he would have been looking at a very expensive (if at all possible) repair. As some of you probably know, the A600 and A1200 are known for leaking capacitors ruining your day. It starts as a small leak and before you know it, the electrolyte has eaten through the traces around the capacitor. This is an example of what to look for. These are two SMD capacitors right beside the IDE header (but actually responsible for the video circuitry). The shiny solder blob is how they should look, the lower blob is dull and may have a yellow/greenish gunk on the surface. If you spot this in your Amiga you need to find someone with a soldering iron pretty quickly. Oh, and don't just replace the bad looking ones, if any have started to leak, then the rest will start leaking pretty soon. On this particular board, half of the 18 capacitors have already leaked.


Bryce.

[Bryce]

And this is why you always replace ALL capacitors, not just the ones showing obvious signs. The capacitor in the centre (C236) is the one that looked ok before removing it. As you can see here, the extent on the damage is a lot worse than you'd expect and all 3 capacitors in this picture have started eating away at the copper traces.

Bryce.

[Bryce]

After some extremely careful cleaning and some gentle attention with the Fibreglass pen, it looks like we've dodged the bullet this time. The big copper track between the two capacitors has been damaged, but not broken through, so some tinning will restore it. I re-tinned the pads already and the lower pad of C236 needed to be re-glued as it was floating, but otherwise the new caps can be mounted without any further work.

Bryce.

[chinnyhill10]

After some extremely careful cleaning and some gentle attention with the Fibreglass pen, it looks like we've dodged the bullet this time. The big copper track between the two capacitors has been damaged, but not broken through, so some tinning will restore it. I re-tinned the pads already and the lower pad of C236 needed to be re-glued as it was floating, but otherwise the new caps can be mounted without any further work.

Bryce.

I watched someone do my A1200 and it was a case of just caught in time. The early SMD stuff seems to be quite fragile. With the amount of kit I have here, frankly recapping some of it terrifies me. Although I guess for through hole it's less critical as damage will be caught in time easier.

[Bryce]

I watched someone do my A1200 and it was a case of just caught in time. The early SMD stuff seems to be quite fragile. With the amount of kit I have here, frankly recapping some of it terrifies me. Although I guess for through hole it's less critical as damage will be caught in time easier.

The through hole capacitor technology and manufacturing process was much more mature by the time the Amiga came out. They rarely leak, especially as they aren't exactly being taken to their limits and the temperature isn't high either. They are a pain to change on the Amiga too, because they are soldered to the ground plane, so you need a decent iron (and patience) to desolder them.

Bryce.

[||C|-|E||]

Mega CD 1 also has quite a few of this early surface mount caps... and they also tend to leak. Replacing them is a bit of a bit of a pain too. I mean, it is fine but I prefer to replace the hole through  SEGA went back to the "normal" ones in the Mega CD 2, probably because they realized that the others were problematic. Very neat job you did there!