Electrolytic capacitors are conditioned when manufactured by applying a voltage sufficient to initiate the proper internal chemical state. This state is maintained by regular use of the equipment. If a system using electrolytic capacitors is disused for a long period of time it can lose its conditioning, and will generally fail with a short circuit when next operated, permanently damaging the capacitor.
Qty. | Part # | Description | Price | Ext. Price |
| 6 | 493-2088-1-ND (http://search.digikey.com/us/en/products/UWX0J101MCL1GB/493-2088-1-ND/590063) | "CAP ALUM 100UF 6.3V 20% SMD" | 0.44 | $2.64 |
| 3 | 493-2105-1-ND (http://search.digikey.com/us/en/products/UWX1C101MCL1GB/493-2105-1-ND/590080) | "CAP ALUM 100UF 16V 20% SMD" | 0.47 | $1.41 |
| 2 | PCE3859CT-ND (http://search.digikey.com/us/en/products/EEE-0JA330WR/PCE3859CT-ND/766235) | "CAP ALUM 33UF 6.3V 20% SMD" | 0.49 | $0.98 |
| 1 | P5114-ND (http://search.digikey.com/us/en/products/ECA-0JM471/P5114-ND/244973) | "CAP ALUM 470UF 6.3V 20% RADIAL" | 0.25 | $0.25 |
| 1 | 493-2118-1-ND (http://search.digikey.com/us/en/products/UWX1V220MCL1GB/493-2118-1-ND/590093) | "CAP ALUM 22UF 35V 20% SMD" | 0.51 | $0.51 |
| 1 | 493-2083-1-ND (http://search.digikey.com/us/en/products/UWX0J220MCL2GB/493-2083-1-ND/590058) | "CAP ALUM 22UF 6.3V 20% SMD" | 0.50 | $0.50 |
| 1 | 493-2099-1-ND (http://search.digikey.com/us/en/products/UWX1C100MCL2GB/493-2099-1-ND/590074) | "CAP ALUM 10UF 16V 20% SMD" | 0.48 | $0.48 |
| 1 | PCE4304CT-ND (http://search.digikey.com/us/en/products/EEE-1HA4R7NP/PCE4304CT-ND/946239) | "CAP ALUM 4.7UF 50V 20% SMD" | 0.71 | $0.71 |
| 1 | PCE4643CT-ND (http://search.digikey.com/us/en/products/EEE-1VA4R7AR/PCE4643CT-ND/1718066) | "CAP ALUM 4.7UF 35V 20% SMD" | 0.50 | $0.50 |
| 1 | P1142-ND (http://search.digikey.com/us/en/products/ECE-A0JN470U/P1142-ND/227583) | "CAP ALUM 47UF 6.3V 20% RADIAL" | 0.30 | $0.30 |
| Subtotal | $8.28 | |||
| Shipping+Tax | $3.15 | |||
| Total | $11.43 |
Aluminum capacitors are made by separating an inner and outer aluminum electrode by a layer of electrolyte paste contained in a porous spacer. When a voltage is presented across the plates, a chemical reaction occurs at the surface of the aluminum, forming an Aluminum Oxide layer on the surface of the aluminum plate. The Aluminum Oxide is a dielectric, and the layer is relatively thin. Two conductors separated by a dielectric make a capacitor.
When the paste dries out, the capacitor is no more. If you reverse the voltage, the dielectric layer breaks down rapidly, gases can form, and the capacitor will go "pop" (or sometimes "boom").
Tantalum capacitors are made by forming powdered tantalum around tantalum wire. The sintered pellet is dunked in an acid bath and DC is applied across the pellet. Current flow causes Ta2O5 oxide to form on the surface. A maganese oxide layer is formed over the pellet by dipping it into Mn(NO3)2 solution and then heating. A wire is then bonded to the outside of the pellet. A tantalum capacitor has extremely thin dielectric, resulting in easily obtained high capacitance values.
Unlike the aluminum capacitor, there is no electrolyte to dry out. Since it is dry, its lifetime is much longer, and it also has a lower leakage current. Tantalum capacitors can also handle some reverse voltage without failing - but not much. Because of their smaller physical size, the voltage rating of tantalum capacitors is lower than aluminum capacitors.
| (http://i237.photobucket.com/albums/ff216/Sephiroth1975/General/LeakyCaps2.jpg) (http://i237.photobucket.com/albums/ff216/Sephiroth1975/General/EEWorkStation.jpg) | It's a complete disaster! Every last one of them, EVERY ONE, had leaked! I intentionally rubbed the bottom of a few of 'em on the towel so you could see the syrupy electrolyte solution. You can see with 3 of the big capacitors being flipped over that the plastic seat is all gooey and discolored from that stuff... I had a lot of cleaning to do under EACH one! I dunno what the standard recommended solution is, but what I used was automotive Brake Parts cleaner! I would spray it on a small piece of towel, and wipe the affected area down. Now, the stuff is strong, it cleans great and completely evaporates very quickly, but if you get it on certain kinds of plastic, it's game over for 'em (it'll mildly melt 'em)! Anyhow, now I must sit quietly till the new capacitors arrive hoping for the best! |
i use ceramic chip caps and tantalum instead.Oh that would be so much easier!
they cant leak
i use mostly the same values
Good luck on soldering on those SMD caps. Without the right equipment and only using standard soldering iron, those are a pain in the a$$ to solder on.
If you're fancy like steve, you use the solid caps, if you're not so fancy like me, you use leaded caps and just dont reinstall the RF shield plates. You can use the SMT types, but they are a little more difficult to install.