I feel a little stupid and mad about a mistake I just made on a project of mine. But I am wondering if anyone knows how to fix it. This is mostly directed at dragorn, because he told me he's got some SMT knowhow.
Some background: A month ago I fried a 16 pin SMT motor driver chip on a pcb I bought. The pcb is supposed to handle a motor, a heater element, and temperature feedback from a thermocouple. The mini potentiometer was adjusted too high, which the instructions I was following listed as a "step 10: oh, and if you plug it in and the board fries in step 5, here's why". I was pretty sure it was dead, so I bought a new board ($45).
Today, I started to test with the new board. I turned the pot down, and hooked up the motor. It worked as expected this time. I moved on to the heater element and plugged that in. My software had a 'turn heater on' button, next to a 'ramp' button that I notice after it was too late. (the instructions for this project are terrifyingly disorganized so there isn't much for directions). Now a different chip fried, looks like a power transistor, 3 pins. Now it's shorted, and the light indicating that it's on or off is always lit.
http://www.flickr.com/photos/36318517@N00/sets/72157625888731126/
What do you think? Salvigable maybe?
Alright. Let me know the next one you'll be at or if you change your mind, I just got a pneumatic solder remover in the mail to help w/ desoldering stuff & can bring it to a meeting.
Good news, i'm pretty sure i figured out why the board fried and it's closer to being fixed than it was before... bad news is i'm not going to be at the meeting this week. I'm feeling beaten down by overtime and more physical labor than i anticipated at work.
Bring the board and I'll bring some of the tools and we can see if we can get that chip off.
There's wifi available nearby if you don't mind "borrowing".
Next week I'll plan on bringing some gear to the church to try to pull that chip for you.
Great! I can't wait to see what you've got. The church doesn't have wifi, so I always plan to bring whatever documentation I can. Bruce has let me use his mobile hotspot a couple times and with my new phone I may be able to do the same.
I found a 'software fix' through posting on the project forums that will help get around the issue for the temporary. I plan to switch the output for the heater element to an agacent block for testing through the code. I'm planning on bringing all or part of the project to this week's meeting, and probably will be working on it each week from here on out. There's still a lot to do, but I did have some big successes over the weekend as well, not all bad news. My motors all work... in only one direction, but they work. :)
I ordered a replacement heater assembly, my nicrome wire heater shorted out in the burnup of the chip. When I recieve all the goodies i ordered as replacements, it will move forward, fingers crossed.
Does the church have wifi?
Actually zooming in on your photo it looks like that chip got really hot at some point and already started melting the screwdown terminal block, am I right? Looks like there's some melted blue on it.
Yeah, 2 ways to remove it.
1 - Wick, flux, care. Upside - protects those screw-down terminals more. We could try this at a meeting.
2- Hotair rework. This is the "good" way to do this kind of thing, but it can be hard to control the heat. I've gotten fairly good at it, but I wouldn't promise success. Probably something to do in a "dirty" environment (ie, not in the church) since it can lead to stinky melting plastic if something goes wrong.
Step 1 would be to ID the part and get some more. After that it should be relatively easy to pull off the board and putting a new one on doesn't look hard at all.
I won't be at the next meeting, so i can't help then, but some time after would work, let me know so I know to bring the soldering gear, etc.
That looks annoying and a bit fiddly, but probably salvageable. Esp. if you can get the part off the first board. Have you tried removing it with an iron and a wick, yet?