Introduction: Scavenging Parts From Old PC Boards...
Hello there - this Instructable is a little different from the others I've done so far - it builds nothing, yet destroys everything - or almost everything... it's all about scavenging parts from old 'train wreck' appliances and other interesting gadgets. (Maybe there's a website somewhere called 'Destructables' for posts like this?)
Please note: this is NOT a tutorial on soldering or desoldering! It is assumed that the reader has mastered those skills and techniques already... OK.
When I was a kid, the nearest electronics shop (New Standard Radio) was some 17 miles each way on the bus. I got to go there with my dad 2 or 3 times a year - if that. So I learned early on, that if I wanted parts on a regular basis for my crystal sets and rudimentary amplifiers, then I would have to go "scrounging" for them. Old Mr Moore who lived next door, used to build valve/tube radios, and every now and then a small box of discarded parts would come across the side fence to bolster my meagre parts inventory - (carefully kept inside several empty ice cream containers) but this proved to be not as regular as I'd hoped.
Then I got the bright idea that there was probably some good bits and pieces at the local tip - all I had to do was to get there. So I used to borrow a friend's pushbike and also "borrow" some of dad's tools, put them in a bag on the back rack and off to the local tip I'd go! Of course back in those days (1960's and 70's) most tips here in Oz were unregulated 'danger zones'. Rusty old hulks, broken glass and other unsavoury items (resident pests and rodents were in abundance too,) but none of those things phased me - I was oblivious to all of them, and never came home with bites, stings or other injuries.
So what did I get way back when? Well, I scavenged lots of old germanium diodes, transistors, transformers (for coil winding,) loudspeakers, wiring looms, IF transformers (lots of Litz on them for winding better coils,) tuner caps, knobs, pots, switches - anything I could lay my hands on, and remove with my simple but effective tool kit (which included Dad's good 'Stanley' brand claw hammer - I used to call it "the persuader"... and a 10" long chisel - no large part or chassis could withstand the might of the dynamic duo - claw hammer and chisel - ouch!
I lived like that for 8 or 9 years, until I got my first job out of school and could start to pay for my own tools and parts (and travel on the bus at will, to New Standard Radio - with my own money in my pockets and not Dad's!)
Step 1: The Kind of Tools You'll Need...
If you're going to do this successfully, you'll need a basic tool kit, as shown above. You will need:
1. A fairly good soldering iron - at least a 25 watter, with one or two different tips - pencil point and one flat edged. Temperature controlled units are more expensive, but are more versatile.
2. A reasonably good desoldering tool - they can be either plastic or metal - just don't forget to take them apart and clean them now and then!
3. Some solder - WHAT?? Yes - you may need to add extra solder before you can desolder some components - more on this later.
4. Some 'tweekies' - surgical tweezers are one of the best tools I've ever owned - get yourself a pair...
5. Sidecutters - make sure they stay nice and sharp - these are great for removing wiring looms on the larger appliances or boards and also for cutting the nylon zip ties from around those wiring looms - rarely used on components, except large resistors/capacitors that are mounted above the board, not fala to it.
6. Last but by no means least - safety glasses or face shield. This is a must do - particularly when desoldering. Eye safety is paramount when you've got a hot soldering iron in your hands and especially when one slip can result in molten solder being accidentally flicked off the end of your iron's tip! Although this is a rarity amongst experienced hobbyists, it is not impossible, so please - protect your eyes... they're the only ones you've got!
Step 2: What Kind of PC Boards Should I Look For...?
INSERTED SAFETY NOTICE: There is one device that you should avoid - at all costs - the infamous PC power supply! (It looks like the small metal box in the photo above.)
Why? Well it contains a number of high voltage - high value electrolytic capacitors (big, tall, metal 'round things' with a heatshrink plastic sleeve, containing the voltage and values printed down one side.) These power supplies are considered dangerous even by experienced techs - so don't play with them. According to the experts, those capacitors can store a lethal charge for days or even several weeks, and since you don't know when they were last in use, you have no way of telling whether they are safe or not to scavenge from. Stay safe and don't go there... OK.
Well, some are definitely better than others - for instance, pc boards that come from modern day computers and laptops are virtually useless IMHO - more on that in the next step...
The kind of boards that are easiest to get parts from are the older style boards - single sided, wave soldered:
Conventional components harvested from:
1. Old stereos,
2. AM/FM tuner modules, (you can get the ferrite rod antenna coils, quite good ones too, the tuner caps, and quite often the quality of components is better all round in these kinds of things - styroseal caps, metal film resistors etc.
3. Clock radios (you'd be surprised just what you can get from one of those little beasties) - we'll take one apart in an add-on step later on. (Polyvaricon, antenna coil, mini speaker, transformer, 6 to 12 components, 9 volt battery snap)
Instructable on the clock radio is now done: https://www.instructables.com/id/Dismembering-A-Clock-Radio/
4. Old TV boards - beware of exploding cathode ray tubes (CRT's) - you may injure yourself during board removal (never attempt to remove a board from a TV set or computer monitor, by yourself) - best to get them from a recycle centre where staff have done all the hard yards and taken all of the risks. I won't be responsible for any injuries, if you end up doing stupid things to yourselves!
5. Gadgets from various toss outs - leftovers from garage sales are often left on the footpath for passers by to collect
6. Gadget shops often toss unrepairable items into a skip - see if you can scavenge them - legally!
7. Building sites often have offcuts of plywood, short lengths of pvc piping (for crystal radio coil formers,) as well as cut off 'end runs' from the cable drum of mains wiring cable (joined end to end they can make good antenna wires) and other sundry items.
Well, you can just use your imagination to discover and find the rest. Friendly word of warning - don't go "bin diving" (leaning over a bin or large skip) by yourself, especially after dark - or you may need some 'professional' help to get out again (from patrolling security guards maybe???)
One Tip About Desoldering
Years ago, I used to work in the business machine trade here in Brisbane. One day I was out in the back room workshop with the boss and I watched him add some solder to a board that he was replacing some parts on. I looked at him with a grin and said "No Reg! You're supposed to suck the solder off those pads, in order to take those parts out!" He looked back at me with an even bigger grin and said "Well, what if there's not enough solder there to 'suck' in the first place?"
I was a bit dumbfounded by all of this, but when he showed me that it was sometimes better to add a little solder to the bigger lands and pads, I could see his point - the more solder on the larger joins, the bigger the suction the desoldering tool could muster. So, if you've got a 'tough one' (large component) that just won't come out with normal techniques, try this one, before you end up burning a hole right through the part and the pc board!!!
Step 3: Harvesting the Parts...
Hi there folks - I've removed the previous text about 'no soldering' etcetera, and have decided to post one picture - some of the parts I've harvested of old PC Boards in recent times. Capacitors, inductors, transformers (audio and power,) a speaker and several other things that were scavenged elsewhere - like the two thumbwheel switches (bottom right hand corner) and a pair of mini DC motors from an old CD player... Enjoy!
Now we've got to sit down and have a close look at just how to do this. Take your target pc board, and before you start in on it with the iron and the tools, give it a very careful visual inspection. It's not just about what parts you think you might be getting - it's also about making sure there are no hazards on that or any other board in your possession.
Make sure that there are no glass fuses left inside their clip holders - remove them and store them immediately. Make sure that the lead outs from the components underneath the board aren't too sharp for you to handle - you can cut yourself on sharpened cut off leads out - believe me - I know!
Also, if there are any heavy duty devices (power transistors, rectifiers or resistors) that are attached to metal heatsinks, be careful around those devices and their fittings. Power semiconductor devices have a white grease compound used to help make a seamless contact between the flat surface of the heatsink and the device.
Depending on how old the board is, this grease may be carcinogenic - it can cause cancer through prolonged use and handling. More recently, any dangerous cancer causing compounds have been deleted from this kind of silicone grease, making it much safer to handle. If you doubt the safety of ANYTHING you are doing, based on this Instructable - then don't do it! Scrap the board and choose another!
Using a flat surface, place the board face up, and proceed to identify and mark out which parts you want to harvest. Circle them with a Nikko pen, and then turn the board over, face down. Use your soldering iron and desoldering tool, and desolder the lead outs of your chosen 'target' components on the board.
Sometimes it may be useful to mark the underside of the board, rather than the top, or you may be able to fashion a 'board holder' (use a bench mounted vice for example,) so that you can mount the board in such a way so you can see both sides of the board without having to move it around. If you are harvesting from a translucent pc board (eg: Riston board - made of fibreglass,) you may be able to use a bright light on the component side of the board, so you can see the Nikko pen circles around each component from the pc track side of the board.
Get an idea where the component leads are, and then begin. Don't use your fingers as a heatsink! Use some needle nosed pliers and grip the lead out wires of each component while applying heat from the iron on the other side, and when the solder begins to melt, tug the component leads and ease them out of their pc board 'through hole' mounts.
Step 4: What PC Boards Should You Avoid...?
There are some Pc Boards that are just not worth considering. computer "motherboards" and modem boards come to mind, as do 'wireless' modems too (the kind that manage printers, scanners, and other PC peripherals.)
If you examine photo 1 - the two pc boards posted above, you can see that, by far the components mounted on the board are "surface mount" parts. They are too small and fragile to be harvested and used in normal projects, without special tools and expertise. By and large - forget about them. In photo 2 (the closeup of the power supply section of that board) you can see a DC jack (for you 'wall wart' power supply) an on/off switch, some MOV's and other sundry parts which MAY be worth harvesting - or not!
Picture 3 shows the underside of the larger of the two pc boards - totally surface mount components...leave them in the skip!
Pot Of Gold...!
If you do come across some really old appliances (valve/tube radios, gramophones, headphones, boxes of parts from yesteryear etc,) then try not to scrap them in a hurry - they could be vintage equipment, and worth a lot of money! Take some time to ID them on the Internet - take some pics and post them in an appropriate forum - you never know - a good stash of valves/tubes, tuner caps or other oddball components (hard to get) could be worth while chasing up - but only consult the 'experts' - people who have years of experience and nothing to gain or lose by helping you out...
Step 5: Storing Your Harvested Bits & Pieces...
Before you go and empty out the local tip or recycle centre, or mount 'day after' dawn raids on the left overs of the previous day's garage sales, give some thought as to how you will store all of the bits and pieces you have gained.
Buy (or scavenge) one or more sets of drawers - the plastic ones can be expensive, if you want a unit with 20 or 30 small drawers, but if you start with a dozen drawers, and/or one of those portable fishing tackle display boxes, that might be enough for now.
Believe it or not, storing wire and metal parts can be more difficult, so if you're going to go all out and harvest and store a lot of stuff, then maybe you need a large set of wooden drawers, or even a cupboard to store all of your stuff in. Wire can be rolled up and stored in a 'wire bag' or box - metal parts can be stored on old styrofoam boxes, scavenged from the local fruit shop (known locally, as 'Broccoli boxes') they come with a lid, but must be washed out (with bleach, preferably) before you can use them.
The pics shown above are my own 'arrangements, and it has taken some years to gather all the fittings to make it all possible!
So there you go - go get them pc boards and save yourself a fortune in spare parts and relevant bits and pieces...