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Ugh. No undo in soldering!
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Ugh. No undo in soldering!

by psychoboyjack on Sun Mar 08, 2009 12:46 am

Alright, so I'm pretty new to soldering and I wish I could blame this mistake on it but it mostly stems from my misreading the instructions. Ugh. :( My Tv-b-gone came together flawlessly!

I was building my Fuzebox when I noticed that I had put parts where they shouldn't have been.

These little guys (18-22pF ceramic capacitor) were where the 0.1uF ceramic capacitors should have been in C1 and C5. I realized this as I was trying to put in the 28.63636MHz crystal and saw those two little things on the PCB where they SHOULD be and then I looked back at my parts and saw I made the mistake.

Then I tried removing them. I managed to get the C5 one out with very stubby legs and a clogged hole on the PCB and the one in the C1 slot is harder to get out as it's between two capacitors.

I've tried removing all the solder from the joint and for some reason the wick isn't absorbing it all. Brute force while pulling the ceramic capacitor out while heating the other end didn't work either. Ugh.

Please don't wag your finger at me, I already feel pretty slow for making this mistake already. :(

Question is... Do I try and unsolder the other parts on the board, purchase a bare PCB and do it right from the get go (along with buying the two other black tipped ceramic capacitors) or is my project still salvageable?

The clogged hole won't become UNclogged no matter what I do, and the other one in the C1 slot is missing a leg since it broke off after I unsoldered it.
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Re: Ugh. No undo in soldering!

by magician13134 on Sun Mar 08, 2009 1:29 am

Do not buy a new board. Desoldering is a skill you will need to learn. It's totally understandable to have some troubles the first few times. First of all, I would highly recommend a solder sucker, for $5-$10, you can't go wrong. I NEVER start a project without it by my side. Sometimes solder wick just doesn't cover it, I've never liked the stuff quite as much as my solder sucker.

And for the clogged hole, there's a trick I learned here that I have to say, works 100% of the time, is super easy, and you will want to jump for joy when you first try it. Hold the board, component-side up, parallel to the table. Put the iron in the hole in question, if you can, the top is fine, if there's some reason you can't put it in there, the bottom is actually probably better. Heat the hole for about two seconds, then all in one movement, pull out the iron and toss the board at the table. It shouldn't be HARD but not gentle either. The solder will pop right out. Give it a try. You'll be pleased.
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Re: Ugh. No undo in soldering!

by zener on Sun Mar 08, 2009 1:48 am

It is easy to pull out a two leaded part like a cap. Just heat both pads at the same time (very easy if the lead spacing is .1") Then while they are both heated just pop the part out. You can do this either by putting a little screwdriver under it or grabbing it with an alligator clip or similar. Once the solder melts on both legs it basically falls out. Then it is much easier to clean out the hole with wick or sucker or table bang method.

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Re: Ugh. No undo in soldering!

by winch on Sun Mar 08, 2009 2:35 pm

Another trick is to heat the hole and push through a length of solid core wire. The solder gets stuck to the wire and you end up with a clear hole. The lengths of component lead that get snipped off after soldering are ideal for this.
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Re: Ugh. No undo in soldering!

by Amberwolf on Sun Mar 08, 2009 4:27 pm

One more trick you won't believe you didn't think of:

Parts needed:
--A cheap RadioShack-style soldering iron: the kind with a tip held in by a (usually philips) screw from the side at the heater-end
--Brass safety pin with wire no larger in diameter than the hole to be cleared

Steps:
--Unscrew the screw completely out of the iron
--Take the tip out of the iron
--Insert it thru the "spring" hole of the safety pin
--Screw it tightly back into the iron while keeping the pointy pin of the safety pin sticking out like the iron's tip used to
--Bend the other end of the safety pin back out of the way if necessary
--As the iron heats up, tin the safety pin as needed

Now you have a fine-point hole-poker for clearing out oopsies. :) It works for removing SMT solder-bridges, too, sometimes.

On occasion, you may have to cut the point off the pin to make it heat the hole enough to work, or even to use a second iron with a normal tip, especially with a ground or power plane involved (like with most caps).

Someday I need to take pics of this to make an instructable--I keep thinking about it, but always forget to do so!


(The very first use I ever had for this trick was to poke holes in scratch-built models for windows, so I could run fiber-optics into them. A drill simply took too long and sometimes broke bits!)
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Re: Ugh. No undo in soldering!

by eil on Sun Mar 08, 2009 11:19 pm

Do you have liquid flux? If no, get some. And a needle-tipped dispenser to go with it. Whenever you can't get solder to go (or leave) where you want it to, just add some flux and it'll MOVE. Flux is like the Chuck Norris of soldering supplies.
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Re: Ugh. No undo in soldering!

by jarv on Mon Mar 09, 2009 12:30 pm

I would buy this instead of flux if you plan to do any more soldering:
http://www.sparkfun.com/commerce/produc ... ts_id=8775
projects (avr/electronics/programming) - http://jarv.org
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Re: Ugh. No undo in soldering!

by Amberwolf on Mon Mar 09, 2009 2:49 pm

He already has that, according to his post.
Watch me build an electric bike from assorted junk!
Alternative Energy Sources for the Home from Recycled Junk
A subsidiary of Cybernetic Necromancers, Discorporated:
"We Bring Dead Things To Life"
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Re: Ugh. No undo in soldering!

by jarv on Mon Mar 09, 2009 2:57 pm

oh i missed that part.. hm, I have never had the problem of wick not absorbing solder. I guess flux is a good idea then!
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Re: Ugh. No undo in soldering!

by psychoboyjack on Tue Mar 10, 2009 12:00 am

Wow, thanks for all the input! I got pretty frustrated with it so I'm going to leave it until the weekend.

I did make it worse by removing the capacitors and, uh, leaving the leads inside. With solder. My soldering iron doesn't seem to be able to heat the hole enough cos I tried banging it to get it out and nothing happened.

I'm going to learn some yoga, drink some green tea, find zen and try it this coming weekend. Mmm. Nirvanaa.

:D

Thank you again, though. I'll try and get a picture of it up this weekend if I can't make any process of it. I'm glad to see mistakes are more common than I thought. :|
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