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Wanted scrap printed circuit board

cooldan

cooldan

i like pizza
Joined
Jul 21, 2011
Messages
6,456
Location
Ealing, London
hi guys

i have a gas-powered soldering iron that works just fine for my usual needs, which means wires on switches or coils, and maybe the occasional diode. now i'm considering taking the next step up, to soldering/desoldering a PCB. specifically, i want to desolder, remove, replace and resolder diode D3 on my System 11 Rollergames, as i've managed to convince myself this will help.

anyway. i know that probably my soldering iron isn't up the the job, but i also know that my soldering skills are *definitely* not up to the job, and i have never desoldered anything in my life. i bought a suction thingy and a have some of that copper braid stuff, but i just don't know how hot i can go or how close i can work with my butane iron.

so i want a scrap board i can happily feck up and nobody gets upset. i went to ebay, but (unless my search terms were way off) there's not much there, and the sellers want loadsamoney for it.

ideally either someone in London who could bring it to a meet (Matt's Surrey League, or the SE League which is in Camden at the dude's place in a fortnight) or the LPC at the pipeline on the 23rd. otherwise i'm happy to bung a few quid your way via cash or cheque or paypal if you have something you can stick in the post?

advice also very welcome. the butane iron has a hi-lo power sliding scale, so i'm assuming it should be at the shallow end?

odd couple.jpgodd japanese men.jpgodd streaker.jpg
 
of course, i could always seek out some piece of crap old equipment in the house to break up, but i'd rather it was a board from a pin, as this is more realistic to my needs.
 
You'll have to remind me before hand, but I can bring a old PCB to the LPC for you to play with... :eyebrows:
 
I decided to go for a more controlled electric soldering iron for PCB's because the gas ones kick out a lot of heat and have a wider tip. You are welcome to make use of the fruit machine PCB I was given by John Oliver for me to practice on, I am not using it right now and can alway pop over to collect it. Drop over any time to collect it, just make sure I am in. :eyebrows:
If not, I can drop it in next time I am local to you.
 
thank you to both of you, very kind.

assuming i don't buy a second soldering iron at this stage, what do i need to know about trying to remove and replace a diode using my gas one? low heat, ok. croc clips attached to part being soldered to take away heat? any other tips?

diodes are about 15p each so if the board is free then i can happily keep on trying til i manage to do one that isn't a complete dog's dinner, before doing it for real on my real board. of course, i could also think about bringing the board to Cal, or asking him to bring his fancy iron to me, if it seems i'm trying to do something that just isn't gonna work out
 
Soldering to a pcb is easy. Desoldering.. can be harder in my limited experience.

Worst case scenario is that you end up lifting one of the pads from the board. (the pads are the copper circles at the end of the tracks that surround and go through the hole in the board)

When that happens, usually due to applying to much heat/too long, then things start to get ugly fast, as the replacement component won't solder into place easily.

I just shelled out £80 or so on a fancy temperature controlled desoldering iron/pump combination thing. It seemed cheaper than having to buy a new board when I inevitably would have cocked up. Some people get on fine with manual suction pumps/braid. Turns out, I am not one of those people.

My tips. Snip the component off the board, then desolder. Either warm up the solder and *gently* lift out the remaining pins (you dont want to be pulling hard for fear of wrecking the pad), or just try sucking it out with pump. If you can't get the hole clean, or just having trouble in general, applying a small bit of new solder may help. The flux in the fresh solder may help melt old solder, and then the suction pump should bring out the old & new solder in one sweep.

Good luck!
 
cheers Paul, i really appreciate your efforts to understand where i'm coming from. one question though - if i'm just snipping something off the board, why should i bother to desolder at all? can't i just solder the replacement part to the amputated leg stumps from the old diode or whatever?

no idea.jpg
 
Well I guess you could try doing that, but
a) you would be mocked for your soldering skillz
b) Would probably be really crap conductivity
c) It's probably harder to solder a new component to the remaining stumps than it is to do it properly. The component legs should pass through the board, then you can spread the legs out (oo-er) on the reverse of the board to hold component in place whilst you solder it in

Clipping the component off the board just makes for easier access for desoldering the remaining stumps and cleaning out the holes. Again, all in my experience, your mileage may vary etc etc.
 
If I can do it, you can do it. I have a cheap soldering iron, a cheap de solder sucker from eBay and I managed it in a few minutes without borking anything!
 
John Oliver (my hero) demonstrated a method where he uses a small stick of wood to tease out the snipped legs. I use kebab sticks.

So as Wizcat said, snip the component off the board at the legs, apply enough heat to get the solder liquid, use the sucker to pick up the old solder, if legs do not get sucked up, reapply heat and use the wood to gently stroke them out. I tried tweezers but by the time I got to getting hold of anything, the solder had reset.

I respect that Cooldan asks for advice and help before he tries something. Soldering can be daunting for some people but practice does make it easier. I have recently gone around the house and found electrical items that were no longer working and used them to troubleshoot and repair. A great way to practice.
 
Calimori said:
John Oliver (my hero) demonstrated a method where he uses a small stick of wood to tease out the snipped legs. I use kebab sticks.

So as Wizcat said, snip the component off the board at the legs, apply enough heat to get the solder liquid, use the sucker to pick up the old solder, if legs do not get sucked up, reapply heat and use the wood to gently stroke them out. I tried tweezers but by the time I got to getting hold of anything, the solder had reset.
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Click to expand...

Hemostats are a great item for this sort of work, clamp them on the top side of the component leg, put soldering iron on the bottom side but with the board upside down. when the solder get liquid the weight of the hemostat pulls the leg or whatever out.

Or buy a duratool desolder station (awesome)

Cheers
Ian
 
That sounds like a very good tip. I might even know of a cheap source for small ones. Thanks Ian.
 
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