The power supply of my model railway got broken.

I think the problem is the capacitor shown in the image. So does somebody know which kind of capacitor this is?

enter image description here


closed as off-topic by Nick Alexeev Apr 22 at 23:48

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the repair of consumer electronics, appliances, or other devices must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired. See also: Is asking on how to fix a faulty circuit on topic?" – Nick Alexeev
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 7
    \$\begingroup\$ Looks like a 100 µF 35V electrolytic capacitor. \$\endgroup\$ – evildemonic Apr 22 at 15:55
  • 1
    \$\begingroup\$ Measure the diameter (and height if there is a height restriction) with calipers. It tells you the specific package required for the replacement otherwise it may not fit onto the PCB. \$\endgroup\$ – DKNguyen Apr 22 at 17:48
  • 1
    \$\begingroup\$ Looks to me as though whatever is to the left of that capacitor is possibly the real cause of the problem. The cap itself looks fine other than a bit of gunk on the side from that other thing. \$\endgroup\$ – brhans Apr 22 at 18:07

It's a 100uF/35V aluminum electrolytic capacitor. Aluminum electrolytic capacitors do not, in my experience, use the 3-digit system. From this datasheet:

enter image description here

I see what appears to be flux on the PCB, but often caps will bulge up if they are dying. If it has actually leaked from the cap, then it should be replaced.

  • 2
    \$\begingroup\$ You are right about the 3 digit capacitance code. A second look at the datasheet linked by Enginerd shows that the three digit code applies to the part number, not the marking. \$\endgroup\$ – JRE Apr 22 at 16:39

That is an aluminum electrolytic capacitor.

100 microfarad, rated for 35V.

I'm not sure there's anything wrong with it, though. It has score marks across the top. If it had gone bad, then it would have burst along those lines.

It looks like there's some glue on one side, but that's about it.

The trace to the left of it looks burned.


The capacitance value I state is based on the assumption that the "100" marked on the capacitor is a three digit code as apposed to the literal capacitance of the capacitor. This may not be the case, I am leaving my "answer" in the hope that someone can clear this up. -Edit

Second Edit. I did more digging and it looks like indeed this cap is 100uF, and what really sealed it for me is as Sphero Pefhany pointed out, a 10uF rating would only need a two digit marking as would any value up too 99uF. So it must be 100uF -Edit

That is a surface mount aluminum electrolytic capacitor It is rated for 35V with a capacity of 10.0 uF.

The "100" is a code that translates as first digit followed by a second digit finished by a power of ten digit. The scale starts at uF, for example to get 47uF the code is: 470, or if you have a code of 331 that's 33 * 10^1 uF or 330uF capacitance.

A chart with capacitor codes can be found in this document. link

  • 5
    \$\begingroup\$ No, it is 100uF. In fact the photo in your link shows how 10uF capacitors are marked, which is different from the part number. \$\endgroup\$ – Spehro Pefhany Apr 22 at 16:37
  • 3
    \$\begingroup\$ I Agree with Sphero Pefhany. \$\endgroup\$ – MikeTeX Apr 22 at 16:54
  • \$\begingroup\$ @SpehroPefhany You are right that the chart (STANDARD VALUES AND CASE SIZES) data sheet I posted is explicitly for a part number breakdown and not necessary related to the actual markings on the cap. However I have seen this convention used for many capacitors with this type of form factor which is how my answer came about. I can't cite any actual standard nor can I find a source that states when the actual value or an abbreviated value is used. I'll update my answer to highlight this ambiguity. \$\endgroup\$ – Clipboard_Waving_Enginerd Apr 22 at 17:32

Not the answer you're looking for? Browse other questions tagged or ask your own question.