I'm being plagued by capacitors! - Page 1
Forum section: electronics / general

author: slburris
author_rank: Frequent Contributor
timestamp: September 17, 2012, 03:57:05 pm
content: Bah, haven't we burned through all the capacitors made with thefake electrolyte formula? Guess not....I have a ThinkGeek epoch clock:http://www.plunderguide.com/wp-content/uploads/2008/12/thinkgeek-epock-clock-1.jpgRecently, the display digits started visibly flickering. Figuringthis must be something easy to fix, I took the clock apart.On a hunch, I pulled the capacitor at the output of the voltageregulator. Even though it didn't appear to be visiblybulging, this 10uf capacitor measured less than 1uf.Junk!I didn't recognize the voltage regulator, but a quick searchidentified it as the CX1117 from sicore (www.si-core.com).Who? Looking at the datasheet, it says for stability underall conditions, the output capacitor should be a 22uftantalum. Huh, 10uf bogus electrolytic vs 22uf tantalum....Of to the parts box, replaced the cap with a 22uf tant,and it works fine now.Looking at the cap photo, does anyone know who themanufacturer is? The logo kinda reminds me of SGS-Thompson.Scott

author: Amarbir[Lynx-India]
author_rank: Frequent Contributor
timestamp: September 17, 2012, 04:04:48 pm
content: Well,Me too i had a horrid experience on sunday morning .I open my lab and switch on my magnifier ,Blah dead damn .Opened the same checked one capacitor was pregnant and possibly leaked from the top .Checked the other one ,that was ok .Got two replacement philips caps and installed .So far so good .Checked the MJE13003 Transistors on the same circuit .One of it was leaky ,Well no issue got two replacements and Guess What " Fireworks " .The CCFL tube also was bad i got a new one .Got two more Transistors and Replaced the same " it worked .Can someone even have a clue why the first replacement paid did not work haa haa .Nope it was not the cap anymore ,it was something else ? Guess And Guess

author: GEuser
author_rank: Frequent Contributor
timestamp: September 17, 2012, 04:06:58 pm
content: I just do not understand some of these product manufacturers TBO , i have seen inside heaps and heaps of good gadgets like your clock , some really useful , some not but the underlying impression i get is that they actually want them to fail!Some really nifty stuff , let down by a 5 cent cap or a cheap switch which might have probably lasted for 5 or 10 years if the cap or switch was better , i just don't get it .No idea on cap maker , but had to comment ...

author: T4P
author_rank: Super Contributor
timestamp: September 17, 2012, 05:57:33 pm
content: The CX1117 is the same as the LD1117 but i don't know about different manufacturers.My LD1117 modded magnifier only needed a 10uF electrolytic for stability

author: mariush
author_rank: Super Contributor
timestamp: September 17, 2012, 06:14:00 pm
content: 22uF tantalum capacitors are expensive and tantalum capacitors are sometimes not allowed due to the fire and explosion risk. Therefore, electrolytic capacitors are used instead.Also, often the datasheets recommend tantalum simply because they're guaranteed to have low ESR and ceramic capacitors are problematic because they vary their capacitance with voltage and heat - a lot of these regulators work best with capacitors that have ESR between 0.2-1 ohm - electrolytic capacitors of such low capacity value are not guaranteed to have less than 1 ohm ESR.The datasheet may say 22 uF for stability in all cases, but if you're sure the regulator is for 1 A of power but you're only going to use up to 200mA or something like that, you can probably go with a lower capacitance.This imho is just a case of Thinkgeek getting the kit from several cheap Chinese suppliers, without any control or say in the component selection. That 10uF capacitor simply cooked itself to death near the regulator...