A rite of passage for a young electronics enthusiast used to be collecting an array of surplus boards from whatever could be found, and using them as sources of parts to desolder. It was possible with a bit of work and searching to build all manner of electronic projects without spending much at all. Many hardware hackers know their way around consumer electronics from the decade before their teenage years as a result. Secondhand components can still be used, but the type of components to be found has changed, as well as those needed. [ElectricMonkeyBrain] takes a look, and asks “What should you desolder?”.
As a general rule, he lands on the premise that it’s worth hanging on to the expensive stuff rather than the cheap stuff. Large capacitors, power semiconductors, and inductors aren’t cheap at all, and in the case of the inductors they can yield both ferrite parts and enameled wire for rewinding to suit. We’re surprised that he advocates holding on to electrolytic capacitors as a kit of many values is now pretty cheap, but it’s understandable that if you lack the part and it’s there on a motherboard in front of you, it’s worth desoldering. Finally, he discusses cases, something we’ve been tempted by a few times more than we’d like to mention.
In a world of easy online ordering, it’s useful to be reminded that sometimes there’s still space for salvaged parts, after all, no delivery service is as quick as reaching under your bench for an old ATX power supply to raid. As always though, don’t amass too much of it.
“We’re surprised that he advocates holding on to electrolytic capacitors as a kit of many values is now pretty cheap,”
If they are in expensive gear, they might be better quality than some kit from Shengzhen.
Exactly, and this applies also to decent quality consumer level capacitors from decades ago. I have boxes of NOS capacitors from the 70s and 80s bought from TV repairmen closing shop, and their ESR figures are way better than most crap one could purchase today from Aliexpress, Amazon or Ebay. New capacitors should be purchased only from reputable sellers, none of them uses the above marketplaces. Surplus and NOS is another story, but that requires some effort to find a reliable seller.
Couldn’t agree more. For high values and voltages a recent unused scrapped power board can ding both free and high quality. As you say, certainly better than an unbranded assortment.
Especially when you’re one cap short on an order!
My same thought as Ren about electrolytics. From old or top quality gear, a desoldered electrolytic is very likely to be better than anything you can buy these days. My drawer with smaller desoldered parts have names like nichicon, nippon chemical, sprague, even mouser.
I have done a vast amount of desoldering, but have drifted more and more to just keeping old PCB and then when I need a part, go through my pile of boards and desolder as needed.
Paying some attention to the circuits on the boards can be a great way to learn things. Mostly good, but sometimes bad.
I think the same as both of you.
The only exception I make is for paper condensers found in old tube radios.
They can fail in a bad way and are better to be replaced. Their shell can still be kept for housing a modern cap, maybe (as a masquerade, to satisfy the vintage purists).
Its better to just keep the PCB and rob parts as needed.
This is why I have a room full of old boards that I’ll almost never use.
Exactly. I have a fair stock of parts I unsoldered years ago, but I have found it is a much better use of my time to keep the boards intact and pull components as needed.
That’s the method my father suggests, too. Storing things in the good old “junk box”.
It makes sense, too. That way, the components won’t get damaged soon.
The desoldering ASAP people are likely running out of space, I believe.
Especially the young folks living in small houses/apartments.
They have to keep everything tidy and sorted.
So maybe that’s why there’s a different mind set? 🤷♂️
At one point in life, I would salvage everything I could. Resistors, caps, IC’s, etc back when breadboards and wirewrap were the king. In todays world of quickturn PCB’s though, if it’s not a component I can get new, I don’t want to design it in. Sure, I could save a pile of one-off SOIC’s and other oddball stuff and maybe use it in a one-off project, but most of what I find in consumer electronics these days are custom, or bizarre enough that I’m not going to need them. I have enough stock of modern parts for the projects that I want to use that salvaging doesn’t make sense. Eventually you get to the point where you have a selection of 0603/0402 (or whatever size parts you use typically) that those aren’t worth salvaging either, at $0.001 that they cost new.
When I drop resistors/caps and other popcorn components on the floor, it’s not even worth my time picking them up and sorting, they get swept into the bin. The cost of putting the wrong component onto a board just isn’t worth it.
This. As a kid, I learnt soldering and electronics from scavenging TV boards from the repair shop skip. As an adult, I just want repeatability, and can afford the odd cent or two for the convenience.
Always check the electrolytic capacitors, as their tolerance may be out of spec, including the ESR. Otherwise desolder all the things.
+1 for checking caps.
Things like capacity and shorts should be checked.
Ideally, it’s response on both AC and DC should be checked.
Some half broken capacitors may look okay if used in a simple DC circuit, while fail in an RF or AC application (say, as a filter).
ESR.. ESR is very hyped these days, but maybe not so critical in practice. Not in a prototype or private project, I mean. Back in the day™, only a few electricians cared about ESR and the technology worked nevertheless. 😉
Personally, I salvage connectors as well. Sure, some basic JST-connectors may not be worth salvaging, but any larger ones, rares one and/or proprietary ones get both expensive and harder to get in a hurry.
Resoldering was also an excellent education in how solder behaved, for repairs or for assembly in the first place.
Does anyone bother to desolder SMC except for repair? (I still need to learn to work with those. Not at all sure my hands are still steady enough.)
I remember when the MITERS folks invented “wave desoldering” for bulk recycling of surplus TTL boards. Clamp grips on a DIP, hit the other side of the PCB with a blast from a torch to liquify the solder on all the pins at once, yank…
Get rid of it all. Save your time.
Ok almost all ;-)
My parents moved out of their house, there was a huge collection of electronic parts “worth repairing”, a vast amount of computers starting (from around 1988 until end of 2018 from a small business) that were kept as one could need them for this and that or “I want to rebuild my computer from 1992 and play my games”… Lots of hours were now needed to get this junk out of the house. Most of the computer stuff is now sitting in my house (maybe this wasn’t a good idea either), waiting to be dismantled and sorted for recycling. This again will claim some hours of my life… and I came to the conclusion that it’s not wort my time.
It’s hard for me, as I am a person that sees the old value of the stuff, but also the “oh I could use that for I don’t know what yet” guy; but as I see that I passed that on to my daughter… maybe it would be better to really keep only the things that are really, really gonna get used in the overseeable future.
Spend the time with your loved ones, far more important…
I’ve found that with some multilayer PC boards that there is enough thermal mass hidden inside the board that by the time I’ve gotten the solder to melt enough to remove a through hole part (like electrolytic capacitors) I’ve probably ruined the part.
Sometimes, instead of desoldering something from the whole PCB, I take a dremel/rotary tool and cut away the PCB around the component. Then you can desolder it easily. I also sometimes cut away defective SMD-chips instead of desoldering them, when I have no reflow station at hand. That way there’s less stress on the pads than pulling halfway cold pins or frying the PCB.
This is an important lesson & I’d argue a good reason why you should try & desolder all the things.
Ohhh, how I wish I could learn the lessons of the last statement of this article. :D
I’ve always preferred salvaged parts. I like the challenge of using what’s available, even when it’s not quite what I need, rather than the convenience of making a phone call or clicking on a website and having a wait, whilst the motivation, opportunity and inspiration dwindle, for a particular project. I find you learn more that way, even if it’s just patience and new curse words sometimes.
Of interest, a paper was just published last week that provides a design tool for working with old parts. Check out EcoEDA by Jasmine Lu, et al. https://dl.acm.org/doi/10.1145/3586183.3606745
I’m curious just how many devices they have in their database of “things you can cannibalize for parts”.
I really only save things that I cannot realistically obtain or would specifically want to save.
Specifically, I have a collection of weird displays that I would never be able to justify buying new at +$50/ea
https://www.broadcom.com/products/leds-and-displays/smart-alphanumeric-displays
I also have a weird collection of common voltage power supplies that I have salvaged from equipment to make it easier to prototype something.
I have a Tektronix 2430a scope that fails self-test that I’ve been trying to decide what to do with. Might be an unobtanium hybrid HP chip that cooked itself.
Strip down and part off? Save the generic parts for myself and only sell off the Tek specific parts? Dunno.
I m 70 yrs old and ive accumulated a literal ton of parts. Theyre all obsolete now. So Im now in the process of sorting and trashing most of it. Itll be great when Im done, but what a humongous task!
I’ve spent the best part of my teenage years desoldering parts and sorting them in containers. In my inexperience, and desire for parts, I was saving every single part on those boards. Over the years I might have used 10, maybe 15 of those resistors/capacitors, but the rest, is just loads of parts that I know that I will never use. These days I still hog a lot of old electronics, but in my heart I know that I will never use any of that stuff.
“As a general rule, he lands on the premise that it’s worth hanging on to the expensive stuff rather than the cheap stuff. ”
After nearly 40 years of salvaging parts, the above advice is exactly opposite of my experience. My rule is “the cheaper it was in the past, the more it will be worth in the future” and it almost always rings true.
You will use a whole lot of the “jelly bean” components as long as you are doing electronics and if you don’t keep them, you’ll buy them again and again. Even wiring, screws, nuts, standoffs and other hardware will likely get used. Don’t forget to recycle those enclosures and sheet metal parts.
SMD caps, SMD resistors, and transistors are an exception since I can buy cheap “sample kits” from overseas and have pretty much what I need when I need it. Connector kits with standard sizes are available too.
Expensive components tend to be tied to a place and time and their usefulness now is debatable unless you are into remaking or repairing retro hardware (and if that is the case, only save the applicable parts).
A corrolary to my above rule is “if you can’t find it, you don’t have it” which means store, index and catalog your parts. Cheap plastic boxes from HFT and an excel file works great. It’s pretty rare that I don’t have a part in my collection that won’t do the job I need it to do.
I’ve collected a good bunch of components over the course of my life, including some pretty rare things that I’ve never used since…
I found a few years ago a technique for this task, especially for classic thru holes boards : I obviously use a soldering iron, and also an air compressor (normally designed for mechanics). It’s really efficient, fast and the heat sensitive components are happy. On the other hand, the epoxy board is ruined but who cares !