DIY/Soldering fuckup, help!

[user]

Finished soldering my 4th eurorack module today, the turing machine by music thing. Even though I didn't add any extra flux while soldering I noticed the boards were quite sticky and had some specks of solder on them so decided to try to clean them a bit with cotton swabs and 96% alcohol. While doing this a whole bunch of the joints developed a white crust that doesn't look good at all. I googled a bit but got overwhelmed trying to figure out what it could be so I turn to the watmm hive-mind for help. Here's a pic: (feel free to ridicule my crummy soldering skills)

 

This is after going over the whole board, as you can see not all the joints are as badly affected... I used 60/40 leaded soldering tin with a flux core. There's still a lot of flux but I stopped what I was doing when I noticed the white oxidation or whatever it is.   

Anyone have any idea what I should do? I've some distilled water as well but don't wanna try anything else before getting some advice from someone who isn't as ignorant as myself. 

 

[kakapo]

What kind of alcohol did you use?  If it's not isopropyl it may have additives in.  Also you should be using 99%.  It usually takes 3+ goes to get it clean with iso.

It's difficult to see, but it almost looks like the fibres from the cotton wool has combined with the flux.

Post it in the diy section of muffs, you'll get an answer there.

[user]

Thanks! 

Of course I looked up the exact brand of alcohol I used after applying it to the board instead of before... it’s got some bergamot oil in it, supposed to be used as a disinfectant for wounds. 

It does look like the cotton somehow combined with the flux in the picture but I don’t think that actually happened, the white coating is just very brittle and there’s a lot of sticky flux everywhere. 

Did some more reading, and found a thread over at mw where someone had a similar problem. The general consensus was to keep scrubbing until the white stuff disappeared so I just spent about half an hour swabbing away and it’s hugely improved. I won’t risk testing the module until I’ve gone over it one more time with isopropyl alcohol and a brush and it’s been able to dry for a reasonable amount of time though so gotta wait until the isopropyl I just ordered gets delivered. 

 

[TubularCorporation]

This happens to me when I use 99% isopropyl.  I don't have any advice for you, I just don't clean my PCBs at all because stuff like that always happens. I have stuff going back 15+ years that hasn't shown any signs of damage and my Juno 6 has flux all over the main board from like 1982 or whenever and hasn't had any trouble from it so I just don't stress it.

[ignatius]

check the diy forum at muffwiggler. i wish i had advice but i suck at soldering

[user]

Yeah, the flux didn't bother me and I left it on the other boards I soldered. But the little drops and beads of solder worried me because I'm afraid they might come loose and cause problems at some point. After scraping off a couple with a plastic wedge I though fuck it, I'll just clean the whole thing with some alcohol to make sure there's nothing left on there that might go wandering around my case at some point. Then for the first time in my life I was confronted with a white powdery substance that I found unappealing.

 

[TubularCorporation]

Oh I misread and thought it was spatters of flux not solder.  Surprised those didn't just fall off if you rubber your finger over them.

[user]

Yeah, they pretty much did but I’m slightly neurotic and let my ocd get the best of me in this case. “Better scrub it all off, cleanse the board and you will cleanse your soul. Not a single speck of possibly invisible solder must get into your precious case for the contaminants will destroy what’s otherwise pure.” Etc. 

[TubularCorporation]

I learned my lesson about that a few years ago when I tried to reflow the pin header of an LCD on one of these that was a millmeter too high on one end in a hurry before work, accidentally set my cheap hot air station (that just has unlabeled numbers) as if it as F instead of C, and ended up with a bunch of burned flux all over the pin header.  Except when I tried to clean it off it wasn't flux, it was the infill around the traces that I had melted, so now all of the solder traces around that pin header (that amazingly didn't break) were literally just hanging in the air and I had to put a bunch of epoxy all over the hole area, so now it would be really hard if not impossible to ever replace the screen, it looks really ugly, and I probably couldn't sell it for much if I ever needed to even though it works perfectly.

 

Not a good moment but it could have been a lot worse.

[user]

Fuck, I feel your pain. Seems like a great controller. How’s the arpeggiator and sequencer, any good? 
 

I just hope that I learn from my fuckups... gonna brush the board tonight and then check the module in an empty case. 

[kakapo]

Your soldering isn't too bad, I've done a turing machine before and didn't particularly like the pcb board and pads, wasn't a good combination with a cheap soldering iron.

But check your soldering on the right hand side middle section, looks like you might have a faint solder bridge (could be the light on the flux residue) and you could probably do with reflowing that section in any case. 

[andrd]

I'm still a novice with soldering things, but would it have worked to just use a solder wick to pick up all the errant bits of solder left on the board?

[TubularCorporation]

6 hours ago, user said:

Fuck, I feel your pain. Seems like a great controller. How’s the arpeggiator and sequencer, any good?

To be honest, I built it a few years back and they weren't fully implemented back then, so even though I've kept the firmware mostly upgraded I haven't really gotten in to the extra features, I'm using it just as a patch editor/librarian/live control surface and still do any sequencing/arpeggiation externally. It's great over all, my only complaint is that the pots it shipped with weren't that sturdy and the knobs were a tight enough fit that a couple were damaged just by putting the knobs on them, but I swapped in some no-name green Alpes style pots from Aliexpress and they work and feel fantastic, added about $40 to the total cost but well worth it (especially back then when it was a more bare-bones kit and was a fair bit cheaper).

[user]

23 hours ago, kakapo said:

Your soldering isn't too bad, I've done a turing machine before and didn't particularly like the pcb board and pads, wasn't a good combination with a cheap soldering iron.

But check your soldering on the right hand side middle section, looks like you might have a faint solder bridge (could be the light on the flux residue) and you could probably do with reflowing that section in any case. 

Cheers! It seems everything except for the Pulse out is working so it looks like I’ve got some reflowing to do either way. 

Put together a music thing mikrophonie right before the turing machine btw and got a bit annoyed during that one, some of the pads seemed to be outright rejecting the solder and took much more heating than I expected. 

 

[user]

21 hours ago, TubularCorporation said:

To be honest, I built it a few years back and they weren't fully implemented back then, so even though I've kept the firmware mostly upgraded I haven't really gotten in to the extra features, I'm using it just as a patch editor/librarian/live control surface and still do any sequencing/arpeggiation externally. It's great over all, my only complaint is that the pots it shipped with weren't that sturdy and the knobs were a tight enough fit that a couple were damaged just by putting the knobs on them, but I swapped in some no-name green Alpes style pots from Aliexpress and they work and feel fantastic, added about $40 to the total cost but well worth it (especially back then when it was a more bare-bones kit and was a fair bit cheaper).

Definitely keeping this in mind if I ever do end up getting a matrix 1000. Over the last 2 years I've almost pulled the trigger on one about 3 times and kinda regret not going through with it now as they seem to have almost doubled in price by now, from around 400 eu to over 700.   

 

23 hours ago, andrd said:

I'm still a novice with soldering things, but would it have worked to just use a solder wick to pick up all the errant bits of solder left on the board?

Like Tubularcorporation said you can pretty much prod them off using your fingernails or a brush. I started soldering about 2 weeks ago but haven't been able to get decent desoldering results with the braid yet at all but maybe I haven't been using enough flux when applying it. 

[TubularCorporation]

Yeah, the Matrix 1000 is maybe a bit overpriced now, but it's a pretty fun synth.  The current cost is almost the same as what it cost to get the M1k (white panel version, which might make a difference in terms of power supply longevity but I'm not sure), the kit to make the controller (at the original price, not current one), and two spare voice chips from a  reputable supplier (not eBay) just in case. In a pre-Deepmind 12 world that was a great deal. These days, maybe a bit less so, although the modulation matrix is pretty excellent and it does have its own unique sound (not too similar to the earlier Oberheim stuff since it uses CEM3396 chips, which weren't used in any of the earlier Oberheims and haven't been reissued yet so that's also something to be aware of - if one goes it's not cheap or easy to source anymore. Lots of fakes on Aliexpress and eBay but real ones are scarce.

[user]

The Turing machine did have some issues after all; no pulse out, no noise out and had to set the little calibration pot all the way ccw to get a lock. 

One of the pin headers I soldered on was slightly tilted making the connection between the two PCBs difficult. 
So last night I decided to try to desolder the pin header but ended up softening/melting the plastic socket that holds the pins together because I was too focused on navigating the desoldering braid around the pads... I used a metal clip as a heat sink but it popped off at some point and I didn’t bother to put it back on  

I guess there’s a reasonable chance that I damaged other components while doing this, what would be the best way to go about this? Try to get the pin header off and hope for the best or try to carefully remove more delicate components first to prevent (or possibly cause) further damage? 

[TubularCorporation]

I never have much luck getting unshrouded pin headers off in good shape, and they're just a few cents if you buy yourself a few long strips and cut off what you need when you need it.

 

What I do if I need to replace a pin header is desolder with wick like you did, then one by one I heat each pin and then use a pair of small pliers to pull it out of the board AND the plastic part of the header while the solder is melted, then clean up the holes (usually it's a lot easier if you put more solder on and then wick it off, rather than trying to get just a little bit out of a hole - you can also hold the board in one hand, heat the solder from underneath with an iron in the other hand, and then blow hard through the hole - sometimes that works the best) and solder a new header in.

 

When you're putting the pin header in, only solder one pin at one of the corners to hold it in place, then if you need to you can reheat that one solder joint with one hand and adjust the position of the header with the other, since you won't need it to hold solder now.  Then solder all of the rest of the pins, I usually like to alternate from the ends in just to make sure I don't overheat the plastic but that's not an issue if you have a temperature controlled iron and enough practice that you can solder at a good pace.

 

The more you build stuff the more you start to realize that most of it is actually pretty sturdy, and if you're feeling nervous about damaging something just watch this:

 

 

[user]

Thanks so much for the detailed advice! Gonna give the desoldering another go tomorrow, pin by pin like you said. 
 

I would have never thought of soldering the pin headers like that, I’ve been klutzing around keeping them in place with tape or little clamps and have been lucky until now. Doing one pin and then repositioning makes total sense. Looking forward to trying that out. 

Gonna order me a strip of pinheaders as soon as I’m done being completely broke, seems very useful to have around. 

I think I’ve seen that arp cleaning video before. Very satisfying watch that. 

[TubularCorporation]

I forget where I picked it up from but it works really well, it's one of those things that seems obvious after you learn about them, like not soldering any PCB mounted switches, LEDs or pots until after you install the board on the front panel, so you can line them up perfectly with the panel and THEN solder.  Seems obvious in retrospect but I didn't think of doing it until I read it somewhere.

I think it was something like $4 at most for a foot of two-row pin headers, but it makes more sense to get them when you're getting other stuff too, so you can combine the shipping.  One of those things like if you need 8 or 9 resistors  or capacitors or other inexpensive components of a single value for a project you might as well spend a few cents more and buy 100 of them at 2 cents each rather than 10 of them at 15 cents each (Small Bear is a good place to do that, you can get 100 resistors of a specific value for like $2 usually), eventually you start to have all the parts you need to make simple stuff.

[user]

Thanks for the recommendations. I'm not in the us and I couldn't really find any place that was convenient to order from that offered anything beyond 32 row headers so I just got a couple different sizes, pretty sure I selected the right ones (right pitch, pin size and shape etc) from the catalogue of 3000+ pin headers this place had on offer... Also got a bunch of resistors, caps, diodes, leds and a few transistors and pots (they were more costly than I expected!). Also a breadboard so I can finally start trying out the exercises from this electronics book that I got years ago but didn't really think through that I wasn't gonna be able to afford the needed tools and components back then.    

Next up is that clock thing you recommended in the gas thread to modify/circuitbend that drum trigger thing i found a while ago, if it ends in cool results I'll try to throw together a nice samplepack or something.  

[user]

Happy to report that after putting in a new pin header the module seems to be working entirely as it should. The new header's pins were quite bit longer than those of the other 2 that are used to mate the boards so I had to reseat the boards a couple of times to get it working but it ran for a couple of hours last night without any issues. Might replace the power connector somewhere in the future because the pins of the one that was included are really short and the power cable comes loose very easily.

Thanks again to everyone who replied, gave me the confidence and knowledge needed to make it work. 

[TubularCorporation]

Congratulations!

 

I built an MS-20 filter module last week and the spacers that  hold the two boards together are 2mm shorter than the combined height of the male and female halves of the pin headers that connect them, weird little things like that show up with kits quite a bit but the only kits I've ever built that straight up didn't work were Synthrotek (I'd say 2/3 of the Synthrotek stuff I've built either didn't work at all or didn't work well and was never resolved through tech support, whereas 100% of the other kit stuff I've built has been fine).