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

[aankrom]

 Some more tips: speaking of tips, you should tin the tip just like you 
 would a normal iron, but tin the inside too. You only need to tin the 
 tip about halfway up the outside. Sucking the excess solder off with a 
 teflon tipped solder sucker is a good idea too. I don't find much use 
 for those, but I have two anyway. Sometimes the bulb on the desoldering 
 iron can lose it's firmness and therefore some force when sucking solder 
 - a spare bulb saves the day.

 Also, when desoldering potentially heat-sensitive chips, give it a rest 
 between each pin. In fact feel the chip with your other hand to guage 
 how hot it's getting. If it gets too hot, lick your finger and brush it 
 over the chip. Or if you prefer not to work with spittle, keep a moist 
 sponge handy. I suppose there's a risk of lead poisoning in the context 
 of soldering & putting your fingers in your mouth. Maybe. One way to 
 give the chip a rest when desoldering more than one at a time, desolder 
 a single row of pins from a few chips, then do the other.

 I use a clip-on heatsink for parts with long leads that for some reason 
 I'm not just cutting or using a conventional soldering iron. Polystyrene 
 caps come to mind.

 Also if you have a Variac or a Powerstat or other variable transformer, 
 you can make your 45 watt iron run cooler if need be. But be prepared 
 for poor solder-suckage because the solder will cool faster.

 AA

 On Sat, 10 Sep 2011 15:53:49 -0400, aankrom <aankrom at bluemarble.net> 
 wrote:
> 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
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at dropmix.xs4all.nl
>>> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy
>>
>> 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
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at dropmix.xs4all.nl
> http://dropmix.xs4all.nl/mailman/listinfo/synth-diy