Hot air rework station?

[Christian Oncken]

HI!  So happy to find you all.

I'm an electronic musician who's been building and modding synthesizers since around '97.  I live about a mile away just off Cherokee.  

I've recently started getting more into repairing studio gear, and I'm hoping to learn SMD rework techniques to repair some of the more recently manufactured synths I have.

Something that might interest you all, I had an old beloved drum machine (a Roland TR-606) built in 1982 that tragically lost its brain.  The CPU and much surrounding logic got fried and there are no existing replacements for the CPU.  I managed to wire a Teensy 2.0 from PJRC in its place and code a replacement  OS for it from scratch just by studying the schematics.  It sequences and plays sounds now like it did before, stores patterns in EEPROM, and syncs nicely with its brothers and sisters... not quite finished yet but it lives again.

Anyway, I've got a problem with another synth mod I'm doing, its an x0xb0x from ladyada that I built and gigged with for years, and is now getting a complete makeover.  I stupidly placed a DPDT toggle where a DPDT push-button was supposed to be.  I've done the best I can with my cheap iron, solder pump, and wick, but the lugs are just too big in the holes, too thick, and there are too many of them to heat them all up at once to get the thing out without damage.  I managed to pull the 40 pin CPU out of the 606 without so much as a bent pin, but this has bested me.  

I'm thinking that a hot air rework station might do the trick here, but I've never used one and I'm not excited about buying one just to see if it will work to pull one part... Does anybody know where I can get access to one for a few minutes?  

If that doesn't work, its dremel time...

Anybody else into music / synth stuff?  Circuit bending?  

[Ryan/baslisks]

heat gun and a little finesse will get that off for you.

[Christian Oncken]

what heat gun would you recommend?

On Tue, Dec 4, 2012 at 12:16 PM, Ryan/baslisks <basl...@gmail.com> wrote:

heat gun and a little finesse will get that off for you.

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[Ryan/baslisks]

Everyone I have picked up has done the job nicely. Maybe grab the sparkfun one?

[Andrew Ricke]

Don't we have a couple at the space?  Stop by at the meeting tonight if your free.

[Christian Oncken]

hey, the sparkfun one might work, hell of a lot cheaper than a station.  I'll check that out.  thanks!

 

On Tue, Dec 4, 2012 at 12:24 PM, Andrew Ricke <andrew...@gmail.com> wrote:

Don't we have a couple at the space?  Stop by at the meeting tonight if your free.

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[Ryan/baslisks]

just practice before you do it. it can turn badly quick. very quick. take a scrap piece of board and play first.

[EschewObfuscation]

On Tuesday, December 4, 2012 12:07:03 PM UTC-6, Christian Oncken wrote:

... heat them all up at once to get the thing out without damage...

Damage to the board or damage to the part?

The usual approach to this sort of problem, if you can reach and are willing to sacrifice the component (sounds like that's no problem) is to reach in, snip each of the  leads with side cutters, then desolder the  pins one at a time with regular iron. Snipping the leads lets you deal with them individually, rather than having to do a simultaneous desolder operation.

Heat gun works well if you're desoldering everything in sight; may be a little less selective than you have in mind if not.

[Christian Oncken]

I'm not sure if I'll be able to, but I'd like to.  Can anybody just stop by?  Your site says its a "Business Meeting".  

[Ryan/baslisks]

yeah, not the most exciting of meetings but they are usually shortish.

[Andrew Ricke]

I plan on working on a few projects instead, like finish wiring up my POV led display sign.  If I can, I'd also like to try to some welding on the smelting furnace, if the welder can work in the space. 

I am usually there around 6:30ish, the meeting will start around 7:30ish, but I suspect the business meeting will be short this month.  Besides, best chance to meet people are at the business meetings as otherwise everyone is off on their own things.

[Ryan/baslisks]

what I've heard is that we don't have enough amps for the welder to work. WE NEED MORE AMPS! preferably peavey.

[Christian Oncken]

I am trying to salvage the part, but I was afraid of hurting the rest of the board.  My thought was that this would come out pretty quickly and in once piece because I've already removed 95% of the solder with other methods.  The board is (mostly) through-hole so I wasn't too worried about other parts coming off.. 

It it comes down to snipping it out, I wasn't sure that I could get my cutters in there underneath them close to the base with the other parts in the way, so I was just gonna lop off the top half with a dremel cutoff wheel and dissect it from there.  Same concept but slightly more destructive.  

[Keith Rogers]

Christian - Hey there, good to see more folks interested in the group!  I suggest grabbing a Chip Quik kit to solve your solder removal woes.  It is an allow that you melt in with the existing solder to reduce its melting point.  Once mixed in, the solder stays molten for longer, giving you time to remove the component.  I think it's around 10 bucks or so, much cheaper than a hot air rework station... but then this might be a good excuse to buy one :-)  Video below.  -Keith 

http://www.youtube.com/watch?v=7kyaz4Zrd78

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[John Reskusich]

Wow.  That is pretty cool. 

Does the heat damage the chip?  How do v you solder a cop like that back in?

[Keith Rogers]

It acts like low temp solder, check the full video for how to clean up and reuse a chip, is much better than clipping leads!  

[Ben West]

Nice, clean method for IC removal.

The heat from the solder iron wouldn't damage the chip, as long as the iron's tip doesn't sit in contact with a signal pin for too long (e.g. more than couple seconds).  This risk is less so for power / ground pins, as those usually connect with large bits of metal inside the chip and thus can absorb more heat.

Bear in mind that SMD chips are mounted in the first place by baking them to the solder's melting point, package, pins, circuit board and all, in an oven.

Nevertheless, a digital temperature-controlled iron is important for this sort of manual re-work, so that you can turn the iron up to only as hot as it needs to be.

--

Ben West

m...@benwest.name

[Christian Oncken]

I'd seen Chip Quik before when researching how to work with SMD parts.. didn't make the connection to de-soldering through-hole parts though.  The lugs are kinda big for the holes, not a lot of space around the lugs, part of the reason the solder sucker couldn't get it done..   I'm not sure it will penetrate down and mix well but its definitely worth a try.  I'll try a heat gun first, hopefully tonight if you all have one, and I'll pick one up along with some Chip Quik if you don't.

Thanks for all the tips everyone!  Will definitely try to get by there tonight.  

[Xsfx2000]

I have an interest in electronic music, and have messed with Rebirth / Recycle / Reason before.

-got an Oxygen8 midi keyboard.

 

The music I have made, needs work.

-Lloyd

[Christian Oncken]

Thank you all so much for your help tonight.  Nice to meet all of you. I'm going to make time to come up there, I'll bring my teensy powered drum machine and the finished x0xb0x next time.

Thanks again.