Life of capacitors - Page 1
Forum section: electronics / beginners

author: Mati256
author_rank: Contributor
timestamp: October 16, 2014, 11:09:40 pm
content: Hello. I have this old remote controlled toy from 1979 with a lot of capacitors, resistors and transistors.I'm guessing the electrolytic capacitors might have gone bad after so many years so I changed them. The toy is still not working.Do ceramic capacitors go bad with time too? Should I change them just to be safe?

author: Tandy
author_rank: Frequent Contributor
timestamp: October 16, 2014, 11:15:49 pm
content: Not generally no, electrolytic capacitors go bad because they dry out that is not something that happens to ceramics.There is probably another cause, perhaps post a picture of the circuit board might help identify any obvious candidates.

author: Mati256
author_rank: Contributor
timestamp: October 17, 2014, 02:12:12 am
content: Thanks. I will probably open another topic with the circuit in a few days if that's OK.

author: Tandy
author_rank: Frequent Contributor
timestamp: October 17, 2014, 08:28:15 am
content: Probably a good plan, probably best to post it in therepairsection when you have the photo.

author: Seekonk
author_rank: Super Contributor
timestamp: October 17, 2014, 02:21:49 pm
content: Going bad is not a given. I have a box of these el cheapo no name 200uf 10V electrolytics that are way more than 30 years old and each one I've tested with my ESI Videobridge is still in spec. Electrolytics have moisture in them and they lose that at a pretty predictable rate based on temperature. We had a legacy design product we sold and one customer complained they went bad every two years in constant service. I checked the module for temperature and from the cap mfg data sheet, that failure was to be expected in just that time. They may take a little time to reform or it might be random failure. Don't just replace them for no reason.

author: Christopher
author_rank: Frequent Contributor
timestamp: October 17, 2014, 02:28:10 pm
content: A good voltage derating factor for electrolytics is 80%

author: tggzzz
author_rank: Super Contributor
timestamp: October 17, 2014, 03:55:58 pm
content: Quote from: Mati256 on October 16, 2014, 11:09:40 pmI'm just turning my 40yo digital clock (the forst most people had seen!) into a vetinari clock. The ali electrolytic smoothing the PSU still functions well.

author: compet17
author_rank: Regular Contributor
timestamp: October 25, 2014, 10:37:10 am
content: Eletrolytic caps don't like 3 conditions:- heat- high frequencies- high powerHeat is bad by itself because it makes the cap dry out or boil and explode. The other two conditions lead to increased ripple current and therefore to more heat. Worst example are switchmode power supplies. Thea are very densely packed (heat), are working at high switching frequencies (ripple current) and sometimes even high power output (more heat and current)In your case, you have a toy working at DC or low frequencies, low currents (battery operated?) and a lot of cool air inside (I assume). So the capacitors are not number 1 repair target there...My almost 60 year old tube radio works perfectly with its orogonal capacitors, although it's quite warm inside :-)