Introduction: Dismembering a Clock Radio
OK - I promised you folks one more Instructable, so here it is.
Wow - I can see so many useful parts - and all for $5.00! Yep, that's all the clock radio cost me, at the local 'Op-Shop'. Of course not all clock radios are dismembered (like the Borg, on Star Trek) the last one I bought is still a clock radio...
Clock radios are one of those innocuous things that you have hanging around the house (usually in a bedroom somewhere) and of course, they don't give you much trouble - until that pesky alarm goes off, and it's usually at some inordinate time - like at midnight last week - and my bedroom is right next door to my neighbour's bedroom too, so I quickly shut it down and went back to sleep :) Of course, you may have wanted to yell at your own clock radio for similar reasons, but the better alternative forms a final solution - turn it into 'spare parts'.
So, the first thing we do, check underneath for a 9 volt battery compartment. If there's a battery in there, you can test it later on as many of them are only a few weeks or months old and may still be good enough for a low power consumption project.
The next thing to do is to take the back off - there's usually 4 or 5 screws in the underside of the plastic casing. Make sure you've got them all - it's not uncommon to find the 'secret' screw inside a battery compartment, or behind plastic moulded 'stoppers' designed to prevent "little fingers" (kids) from tinkering with such things, so when you've found and removed all the screws, carefully jiggle the two halves of the casing until they separate, and then you'll see something like the picture up above. A largish pc board, with lots of 'goodies' on it and around it.
Step 1: Step 1: Identifying the Parts...
Before you go after the pc board a fittings with your tools, find the screws that hold the pc board in place. there's usually 2 or 3 of them, and sometimes there are several plastic clips around the edges, holding the board in place. Once you've removed them, and/or undone the clips, carefully remove the board, and then judiciously cut any connecting wires between the pc board and any other item - and cut them AT THE BOARD end, not the external item end! Some components have their wires attached internally back at the factory - if you cut them too short you may render them useless.
Now let's see, there's a mini 8 ohm speaker and connecting wires - definitely have that one - they can be as dear as the clock radio's 2nd hand price ($5.00!) so there's your money back, if it's a good quality one (large magnet, mylar cone). Then there's the very large 4 digit green LED display. It's a 'multiplexed' one, so you may be able to use that in another project, such as a volt or amp meter later on.
Followed by the AM radio's tuning coil and the polyvaricon tuning capacitor. If you're into building crystal radios or those MK484 TRF receivers, these 2 parts will be invaluable. A decent coil and small tuner cap can cost $5.00 to $6.00 between them, so once more, there's your money back... and then there's all the smaller parts...
On this particular board, there were 2 LED indicators, 5 mini push button switches, lots of electro caps, 8 or 9 mini diodes (Schottky diodes - good as AM radio detectors and also good for a switching matrix,) so all of them can be retrieved. the 455 khz filters and ceramic resonators are a good score as they can be hard parts to buy in many electronics stores. There were also some lengths of rainbow coloured hookup wire - these make life a lot easier when wiring up a new project - a definitely "scavengable" item. Oh, and don't forger the 9 volt battery snap...
Finally, there's the AC to DC power supply - in this case, a rather simple affair - mains transformer, rectifier diodes, and 2 electrolytic filter caps, with an on board fuse.
You must be VERY careful in wiring up and reusing these power supply boards - make sure they are encased in a proper ABS plastic box, with all connections and test points inside the casing - accidental contact with the mains side of such a Power Supply Unit could be harmful or even fatal - don't take unnecessary risks - it may be far safer to use a fully sealed "wall wart" PSU.
Definitely CUT THE POWER CORD OFF THEM and DO NOT let kids play with them!
What you can see in the photo above took about 10 minutes for me to scavenge, and it will have saved me some $20 to $30 on parts, over time. You have to be careful unsoldering the smaller components, especially the diodes as they are heat sensitive. If you think a component could be damaged by heat from the iron, use a crocodile clip as a temporary 'heat sink' on its lead out wires to siphon away any excess heat - and don't get your fingers burnt in the process!
Step 2: Step 2: Raiding the Radio...
I'm adding another Step to this Instructable so we can talk more about the radio. This device is known as a 'clock radio' and it is basically divided into 2 parts. The photo above depicts the 'radio' half of the pc board, and as you can see, many of the parts from this board have already been stored in my parts boxes and drawers. :)
What's left is the specialised chip (IC) and its surrounding components. There are half a dozen or so electrolytics, and 2 metal canned coils. One of these (up in the far right hand corner) is the Medium Wave oscillator coil - the other one is the MW IF transformer for the AM radio band. These coils can be very difficult t remove and reuse, so great care must be used in unsoldering them from the board. Perhaps the use of desoldering braid (known locally as "Solder Wick") is the best way in - using minimal heat, just desolder one IF coil pin at a time, allowing for the board and tracks to recover between each attempt.
There are also 3 'little red things'. They are ceramic filters or resonators, also to do with the AM and FM parts of the tuning section. The polyvaricon tuning capacitor and the tuning coil are already gone, but you can see a few other parts also, like the 2 small copper wire coils - these are part of the FM circuit and help the tuning capacitor select stations on the FM radio band. There is one transistor and a couple of very small Schottky diodes on the left of the board. Try and recover them if you can.
The main IC is a special one and is probably not worth recovering. Even if you have special desoldering tool t do it, it's not worth it. Harvest the small parts, and store them away fro a 'rainy day' when you can't get out, or when your local parts store may not sell what you can easily scavenge. down in the right hand corner, you can see a 5 kohm trimpot. with a basic knob installed, this becomes the volume control for the audio amplifier, which seems to be inside the chip.
Step 3: Step 3: Storing the Parts...
This is just really an endnote to encourage you to think about storage options. If you're just going to harvest parts from pc boards occasionally, then the fishing tackle display box is probably ideal, and all the storage you may need for quite some time. It's compartmentalised, strong, and you can use a permanent marker to write on the outside of the lid what each compartment holds so you can track down needed parts fairly quickly.
If you need more hints and tips on scavenging parts, see my other recent instructable here: