simple component question

[guitarmonky55]

ok im scavenging some old broken toys(rc cars etc) for parts, and found a treasure of resistors that are right in range with guitar pedals, a bunch of op amps that i have yet to identify, and a bunch of what appear to be silicon trannys.  got about 10 good sized working leds too among other stuff.

anyways i have some questions as this is my first time really working with removing components.

1)as i started to remove a few resistors, i noticed a browning around the edges near the leads when i de-soldered it that i didnt notice before........im not sure if its burning or not? so i tried to purposely burn another resistor and it didnt work.  is it easy to overheat resistors when desoldering them? if so what are the signs that one has been ruined?  im using a 45 watt iron from sears.......dunno if that may be too powerful?

2)after i remove the solder(i use a solder sucker bulb from radio shack) the parts still want to stick in the board.  what do you guys generally do to get the parts out cleanly without messing them up too bad?

3)how do i go about identifying transistors, op amps and such that i find on a board?  i can figure out basics like caps and resistors...but i was looking at the trans and couldnt quite figure it out.

[Hal]

sorry the post cant be longer, but gotta go to bed.

1. odds are against it.  I use a much smaller iron, though.

2.  This has been BEATEN to death.  search for 'recycled' 'pulls' or something like that

3. google.  Some are proprietory house numbers and you won't find anything, though

[niftydog]

I conquer, this subject has been well discussed previously. but, some more info never goes astray I suppose...

it's very difficult to ruin resistors with a soldering iron.

You are wasting your (precious) time desoldering resistors. They cost 2 cents a piece or less in bulk and not much more than that in small quantitys. I conservatively estimate my time at around AUD$50/hour. That means that I could either spend 10 minutes desoldering a dozen resistors, or I could just spend that $8.33 and get me a pack of 500 assorted resistors.

Best solution to no. 2 is to have a desoldering iron... but they are pretty pricey. If you don't care about the board you're desoldering, just use a pair of pliers to yank the part out of the hole while you hold the iron to the solder. Careful use of desoldering braid does wonders too. Other people use toothpicks to clear the holes.

no.3 is easy. Google till you drop. If it ain't on google, it's likely not worth bothering about for DIY stuff.

...and, the broken record comment;

electrolytic caps have a limited life and are generally not worth desoldering from old circuits.

In fact, I maintain our spare parts section at work, and any electrolytic that's over 2 years old is considered highly suspect and in some cases we toss them out.

[guitarmonky55]

i know resistors are a dime a dozen but I wanted a 68k resistor that i didnt have on-hand and didnt feel like heading to radio shack last night.  

i havent bothered with the electrolytics, i picked that one up pretty fast reading around here.

looks like all thats left is to hit google and look up these op amps.

[Hal]

resistors are deff. not a dime a dozen at radio shack...more like $.20 each! (I think even a bit more than that by now...)  That is deff. a good time to desolder resistors.  I also pull carbon comps, becuase of their magical mojo powers.  Besides for that...eh

If you haven't found it when searching, some people have good results desoldering with propane tourches.  I've never tried it myself.

[aron]

In general, I buy resistors in bulk and use more than one if I can't find a value.

Cool to reuse if you can do so easily.

[niftydog]

sure, if you're desparate!

But sheesh, anyone paying 20 cents for one resistor needs their head read!!!

[MartyB]

Yep, pulling resistors and any kind of cap from other sources doesn't make economic sense, is self-indulgent with time, but I'll tell ya...for me it's like an easter egg hunt, therapy and I get to play with my soldering iron!  Ninety+ per cent of my 15 or so diy circuits are with recycled parts. I know enough to check/replace caps if something dies.    Maybe its just the solder fumes toxifying my frontal cortex, but these activities are fun to me.  I also learn a bit about layouts, different types of components, mfg. processes.  I find knobs, mechanical bits, connectors, enclosures, out-of production germaniums, tube sockets, all kinds of crap that drives my wife crazy...

[jmusser]

Yeah, that one got beat to death on a thread a started awhile back. I think it fell under "scavenging parts". Two schools on that mostly. People who have a parts stores close at hand, and people who don't. There are even people like me who enjoy actually pulling parts. I actually grab resistors in my finger nails and pull them one leg at a time. If they don't get too hot doing that, then you probably aren't burning them up. the other stuff is a litlle tougher. Most of the brown stuff is probably solder resin.

[MartyMart]

I posted a thread about rescuing parts from a computer monitor about a week ago, here's my feelings after doing it :

1- I did get quite a lot of parts, some nice poly caps, switches, variable resistors and some heat sinks/trannies.

2- It did take a while, and for that reason probably was'nt worth it !

3- I wont be doing it again, unless there's a specific part i need, I can afford to buy "new" parts, which will be more reliable anyway.
Buying in "bulk" always makes things cheaper, my pack of 1000 resistors, which came to about 3 cents each, is still quite a healthy pile.

Marty.