[sdiy] The vagaries of identifying parts scavanged...

[aankrom]

 Radio Shack's 45 watt desoldering iron is a must-have. There are others 
 out there, but RS's is cheap and with proper maintenance will serve you 
 well for a good long time. Plan on using up tips. When you buy the iron, 
 buy at least two new tips. I can go through a tip in one night. Save the 
 old tips though! They come in handy for parts with large diameter leads. 
 Keep the hole in the tip clear. Use a really small screwdriver or old 
 drill bit wrapped tape - don't burn yourself. Also tapping the iron on a 
 hard edge can help. Do it while it's hot of course. Don't smash the tip. 
 Hit just behind the tip. Sometimes the tube leading to the bulb needs 
 cleared or the bulb needs emptied of "rattlies". Carefully undo the clip 
 with pliers and pull off the bulb. Do it while it's hot - you'll see why 
 when you're doing it. I made a makeshift tool out off a coathanger. It's 
 basically a length long enough to go all the way to the tip head and 
 then bent at a 90 degree angle to effect a handle. Hold the iron with 
 the bulb tube opening down and carefully run the coathanger up the tube. 
 Be careful of bits of solder that melt when they hit the tip and flow 
 back. It's mostly charred gunk though. I usually replace the bulb's 
 retaining clip with a twist of wire - makes it easier to remove for 
 cleaning time. After you do this and replace the bulb, give it a good 
 squueeze into a can of some sort. I use a tuna can. After it gets about 
 have full of solder, I use my 200 watt iron and melt it all and I stuff 
 a copper scratch pad into it - instant soldering iron tip cleaner!

 For easy jobs I use a normal soldering iron, sometimes with the help of 
 a small screwdriver to pry the lead up. This is usually when I'm after 
 Dale resistors on a double-sided board. Capacitors I can usually get 
 with just a soldering iron and a couple of gentle tugs. Like when I'm 
 after big mylar, polycarbonate, polystyrene, or polyphenylene sulfide 
 caps. (PPS caps are great for audio and other synth-DIY stuff - not to 
 mention tube circuits, since they're usually rated @ 1600 VDC...)

 For getting choice surface mount parts, I use copper solder-wick, also 
 from Radio Shack. This requires some practice and finesse. I usually use 
 a screwdriver here to pry the part away, with judicious application of 
 the soldering iron for recalcitrant parts. Sometimes you have to get 
 them hot enough for the glue to give way. As you may imagine, it works 
 best for 8-pin parts, but I've got a couple of surface mount NE/SA575's 
 and even bigger parts. As to whether I overheated them, I'm not sure 
 yet.

 It's a good idea to pre-sort your parts as you remove them. Unless you 
 like sifting through a huge pile.

 Recent parts I've got: 4 LF398H's, 4 LF256H's, 8 LM308AN's, several 
 CD4044, CD4028, MC14516 and other somewhat cool parts that I forget.
 I'm still looking for a TA7136. I do have a TA7122. Some cable boxes 
 have uPC1406HA's in them. I found a BL3207 in a karaoke machine.

 AA

 On Sat, 10 Sep 2011 13:28:13 -0400, Noah Vawter <nvawter at media.mit.edu> 
 wrote:
> Funny story: when I was an undergrad I used a blowtorch to remove a
> large number of 74xx components from several 18"x36" circuit boards.
> It was definitely overkill.
>
> AA, do you have some tips for people who want to take apart circuit
> boards easily to get components?
>
>
> On Sep 10, 2011, at 12:04 PM, aankrom wrote:
>
>> Desoldering a part from a circuit board is only half the job. Well 
>> except when you remove parts that you already KNOW what they are.
>>
>> I always like finding the odd FET. Lately I have been finding 
>> 2SK202's. Wonder how they'd perform with audio... Anyway, I was taking 
>> apart a tape deck with several "1212's" & "1202's", my immediate 
>> thought was some sort of pre-biased transistor (and I was right), but 
>> to really know what you have, it's good to hunt for a datasheet. But 
>> alls I have is a number. What prefix to start with? Well I usually 
>> just start with the numbers using datasheetcatalog.com. But you can 
>> get a heap of hits that way. You can try to guess 2SC or even 
>> something like "KTC". Today I discovered a new prefix to try: "SRC", 
>> made my Auk.
>>
>> I used to throw out pre-biased transistors, until I began to find 
>> them in schematics for projects I wanted to build. Fortunately for me, 
>> "throw out" means I just chuck 'em in a big coffee can instead of a 
>> little plastic drawer.
>>
>> Sometimes to identify parts I have to resort to looking them up in 
>> my old hardcopy NTE book or my VERY old hardcopy SK book. (Came in 
>> real handy for a bunch of RCA "Dynascan" parts beginning with "307-" 
>> 'What? It's just a 4030? a 4016? a CA3130?...')
>>
>> AA
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>
> Noah Vawter
> http://web.media.mit.edu/~nvawter  <-   Media Lab documentation
> http://exertion.pbworks.com   <-    Ph.D. research
> http://Synthshopping.com   <-    My commercial wing
> http://kaptheshampoo   <-   webcomic