Multifunction DAQ
Burned out capacitor on PCI-5122 digitizer
I have an old PCI-5122 digitizer that stopped working this week. I took the board apart and found a burned out capacitor (C12) on the larger board near the fan. I'm looking for information on the specifics on this capacitor. Does anyone have one of these boards that they could take a look at for me?
They are not cheap and I definitely have not such a board laying around. However this looks pretty serious and there is a very good chance that the capacitor is only the tip of the ice berg so to speak. The marking of 108 that seems still visible would indicate that it is a 1000 uF (10 * 10^8 pF) capacitor. From the size it looks like an electrolytic capacitor and although it is not clearly visible I think one side of it is beveled, which would even more indicate that it is a polarized component.
Now the big question is the voltage rating. From the image and comparing it to other components, it would seem to be around 7 * 3.5 mm footprint. That's pretty big but not very surprising for 1000 uF.
Most manufacturers only go up to 6.3V for this capacitance, and their housing is usually around EIA 2917 (metric 7343) which would match this here ok. But only at most for 4V. The 6.3V variant would have a housing 2924 (metric 7361) and would be about 1.5 times broader than what we have here.
A little below there is another capacitor which looks like a Vishay Tantalum capacitor and its marking would indicate that it is 33uF 25V (the L means that is is lead free). This is according to this datasheet a 2917 housing and seems to match the one above almost perfectly in footprint size, so it would likely be 2.5V or maybe one of the more exotic 3V or 4V types.
Now, capacitors are of course the one component that will usually go the first (provided the circuit is well designed and with correct component specs), especially electrolytic ones. They do degrade over time and eventually simply break. It's the number one reason for power supplies eventually dying.The problem is that their dying can damage other components around them in the circuit so it may not solve the problem to just replace the capacitor. And even if it seems to work after replacement, there are of course all the other electrolytic capacitors that will eventually go bad too. And as already mentioned the capacitor may have caused surges in the circuit when it eventually gave up its spirit, and damaged other components around it, often not to the point that they will not work anymore, but they are now tainted and not necessarily operating in the originally designed limits anymore and eventually can die too.
