How can I tell if parts are ok? - Page 1
Forum section: electronics / beginners

author: Hextejas
author_rank: Frequent Contributor
timestamp: January 29, 2019, 03:34:32 am
content: I have a bunch of resistors and capacitors that t am trying to reuse. They come from a board that had shorted out the IC.So, I measured all these parts and they read correctly but is there anything else that might have been damaged ?They all read in according to their marked resistance and capacitance. Is there another parameter that might gave been ruined ?

author: CatalinaWOW
author_rank: Super Contributor
timestamp: January 29, 2019, 04:11:13 am
content: Ruined often must be defined in terms of application. Only you can answer some of the questions.For example, resister temperature coefficients may have changed. All parts failure probability will likely be higher than at manufacture, and totally undefined. Capacitors ESR may have increased. Any of these and others may or may not matter for your application.The simple answer though, is that for general use they are probably OK. If you have an unlimited budget you would replace them on principal, but on a tight budget go ahead and use them. If some of them have a problem in your application you will get much value out of figuring out why your circuit isn't working. Learning is always priceless.

author: spec
author_rank: Frequent Contributor
timestamp: January 29, 2019, 09:43:48 am
content: Quote from: Hextejas on January 29, 2019, 03:34:32 amHextejasYour components will be fine. Many of us strip components from scrap equipment.Of course, for any critical applications, you should only use new components, bought from a reliable source.

author: CJay
author_rank: Super Contributor
timestamp: January 29, 2019, 04:08:30 pm
content: The capacitors might have been damaged by overvoltage or spikes and still read nominally within tolerance, I definitely wouldn't trust them on high voltage and electrolytics are rarely worth saving (unless you really have no alternative but to recycle them)Resistors are generally OK to re-use but you need to be careful removing them f4rm the boards because it's possible to damage them by flexing the leads and stressing the end caps however they usually show problems on measurement but they're so cheap to buy it's often not worth the effort recycling them unless they're something special.The value from stripping boards comes form the soldering experience and the general handling of the boards and, if you're cash poor then yes, you can re-use a lot of components.There are other reasons too, I sometimes strip old boards because the look of the components is important if you're restoring things or, occasioanlly, I just don't have the part I need in stock for a quick lash up test.

author: rhb
author_rank: Super Contributor
timestamp: January 29, 2019, 09:36:37 pm
content: Quote from: spec on January 29, 2019, 09:43:48 amFor things like RF relays, pretty much everyone buys scrap as new will give you a nose bleed.I've somewhat concluded that the best way to store salvage parts is on the original board. The exception being things which are fragile. Attach any documentation, trim or tie wires. Configure to store in minimum volume possible.Usually you want some major part such as heat sinks or a transformer.

author: bd139
author_rank: Super Contributor
timestamp: January 29, 2019, 09:50:44 pm
content: I reuse quite a lot of stuff. Resistors, capacitors, the lot. Sometimes it's fun to see what you can build with crap lying around.As for testing, a lot of it is quick finger in the air ohmmeter check and then use it and compare to expected circuit performance. If it doesn't work, debug it then. I rarely if ever get any faulty components other than shorted tantalum caps.Here's an example of something I threw together from a Tek plugin I bought for the sweep IC (to fix another scope), adding only a crystal:

author: spec
author_rank: Frequent Contributor
timestamp: January 29, 2019, 10:30:07 pm
content: Quote from: rhb on January 29, 2019, 09:36:37 pmI learned the same lesson.

author: bd139
author_rank: Super Contributor
timestamp: January 29, 2019, 10:34:14 pm
content: I used to strip the parts off. Can empty a board in minutes. Nothing more frustrating than finding a part on the board you want and then buggering it up desoldering it, which does happen quite often.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 30, 2019, 08:15:54 am
content: I used to have a lot of fun scaging old parts from used equipment.Those old components almost always work well, with the esception of electrolytic capacitors.Over the years this has been changing though.Now I often buy new stuff. I would rather spend I needed to scavange old stuff on building / designing something new.Also, those cheap assortment boxes from Ali / Ebay / China make it seem silly to remove random small parts from PCB's. Why spend time desoldering TO92 transistors when you can buy an assortment of 600 of them for EUR 8. All new and with nice long and straight legs which fit a breadboard nicely.

author: james_s
author_rank: Super Contributor
timestamp: February 03, 2019, 05:51:51 pm
content: Well when you scavenge parts off old boards, you can be reasonably certain that the parts are genuine and not counterfeit junk. I keep a box of old boards around that have either interesting bits, or things that look potentially useful. Often I need some random part and don't want to wait for a new one to arrive so I'll harvest it from a scrap board.