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Author Topic: [Updated] Desoldering a roatry encoder  (Read 973 times)
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Hey Guys!
I'm trying to desolder the following potentiometer:



I need to preserve both the PCB and the potentiometer while doing so. Unfortunately, I'm pretty much out of ideas as to how to approach this.. I tried using a desoldering pump to no extent (wasn't able to suck away enough solder to loosen the connections). I tried heatgunning it, but for some reason (temp. is about 300°C -> 572°F) the solder wouldn't even begin to melt. I was thinking about buying some solder wick tomorrow, but I'm not sure whether it'll be able to remove enough solder or just end up like the desoldering pump did.

Apart from that, do you guys know of any other method I could try to remove that piece?

Greets
Philipp

[Update]
http://arduino.cc/forum/index.php/topic,134202.msg1010585.html#msg1010585
« Last Edit: November 26, 2012, 05:08:43 pm by Christoph680 » Logged


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I find that desoldering wick does do a better job than my soldersucker, but the latter usually suffices. You might find cutting down the the pins and prongs a bit will help. It might also help to apply extra flux to the wick. 
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The biggest problem with desoldering things this big is the amount of heat needed to do the job. Make sure your iron is hot hot and that you focus on one connection at a time, get it really nice and hot to make sure that all the solder is melted and then a solder sucker will be able to clear the hole well enough.

Reducing the amount of metal that needs to be heated up always helps, so cut off the pins as low as possible from the solder side.

You will find the big lugs are the hardest to get clear as they are probably connected to the ground plane on the PCB and you will be heating up a lot of the board in doing the job. Maybe a combination of heat gun for the board and soldering iron to heat up the connection?

Another approach - you may want to sacrifice the pot (which actually looks like a rotary encoder) and get another. That give you the option to snip it off from the component side. smiley
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Yeah, it's 10X easier to sacrifice the cheap component, and save the much more
expensive pcb. Just cut the lugs off on "top", remove the pot, and then it's easy
to remove the lugs one at a time from the bottom, simply by heating with the
soldering iron.

Large devices like pots and multi-pin chips and TO-220 leads are always a huge PITN
to remove without damaging the pcb. Solder wick is generally much better at removing
excess solder than for removing all of it from around a lead.

After removing the part, you can clear the pad out using a stainless steel pin - solder
doesn't stick.
« Last Edit: November 25, 2012, 06:01:20 pm by oric_dan(333) » Logged

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Heat joint with iron and whilst still molten knock circuit board on bench - most of the solder then flies off.
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I've found that desoldering wick has great affinity for solder.  It removes solder it isn't even touching because as the solder it actually touches flows into it, adjacent solder gets pulled in by sufrace tension as well. The stuff works like a miracle.  Don't give up until you have tried it.  I use Chemtronics wick but some others I have used work just as well.  Make sure it says it is a fluxed wick.
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I too have found solder wick to be pretty amazing stuff once you gain a little experience with using it. But I guess that could be said of most all the tools and methods suggested so far.

Lefty
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You need a decent soldering iron that won't loose to much heat when applied to the joint. Use solder wick and a flux pen also helps with lead free solder. Sometime you need to re-flow solder into a joint to melt the entire pool as with solder suck you can remove the top layers of solder but deep in the joint it's still solid and you cant get heat down to it any more. The main problem may be the ground plain as it sucks a lot of heat away. As a last resort you may need to score around the ground plain joint with a scalpel to reduce heat transmission or even use 2x soldering irons.
Try to avoid prolonged high heat as you may lift thin tracks.
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Addendum to what I said previously is, a large problem with trying to remove components
and rework pcbs is that the physical act of trying to remove parts, especially if the pins
are bent, and applying a lot of heat repeatedly, will often break off the pad the part is
attached to, and then you have even more trouble.
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Hey guys!

Thank you all so much for your generous information! I've been able to snip off the leads of the rotary encoder (after looking at it, yea, it is one.. smiley-grin) and desolder the remaining pins - thankfully without breaking any pads. Now that I have the part broken out, I'm not sure what kind of rotary encoder this is. Would I be able to use any encoder that's similar in size and amount of pins? Or are there different versions of encoders? Sorry about the confusion, first time working with encoders.

Greets
Philipp
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Its got three pins one side, two the other.

For the three pins one will be common, the other two are A and B phases.

For the two pins, that's the push-switch - one side is typically ground - from the traces you can see that one side is
routed to the middle of the 3, so that's likely to be the common one of the three.

But hey, why not check with a multimeter and avoid any guesswork??
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It looks to me like a very standard mechanical rotary encoder with integral pushbutton. The 2 connections on one side are the pushbutton, the 3 on the other side are the encoder. There are variations in number of detents per revolution and occasionally in number of states per detent (which is most commonly 4), but they are all very similar. I have a library for interfacing to rotary encoders at https://github.com/dc42/arduino.
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Hey guys!

Thank you all so much for your generous information! I've been able to snip off the leads of the rotary encoder (after looking at it, yea, it is one.. smiley-grin) and desolder the remaining pins - thankfully without breaking any pads. Now that I have the part broken out, I'm not sure what kind of rotary encoder this is. Would I be able to use any encoder that's similar in size and amount of pins? Or are there different versions of encoders? Sorry about the confusion, first time working with encoders.

Greets
Philipp

Almost all encoders work the same way.  There is a +V pin (purely mechanical encodes don't have or need this, ones with integrated electronics do), a GND pin, and two channels, A and B which produce square waves out of phase with each other.  The electronics can tell which way the encoder is moving by how the waves are received.  But most encoders work the same way.  Mechanical ones are the cheapest and have the shortest lives.  Optical and magnetic don't have the same wear potential as the mechanical ones and some are rated for a hundred million rotation life.  I've bought several of these, they are just fantastic encoders, but a bit expensive:

http://www.ebay.com/itm/370592502534

And if you think what he is asking is high, I think the normal <10 pieces price on this encoder was about $60.   This encoder has it's own logic and runs at 5V.

Cheaper mechanical encoder with a nice tutorial linked, maybe that data will help you conceptualize:

https://www.sparkfun.com/products/9117
http://bildr.org/2012/08/rotary-encoder-arduino/
http://www.sparkfun.com/datasheets/Components/TW-700198.pdf
« Last Edit: November 26, 2012, 06:19:04 pm by JoeN » Logged

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