by accident i put TX onto a 12v line of another device and now the breakout board is stuck with both RX and TX on constantly. Anyone think it is possible to fix? What part of the breakout board do you think this misshap would break? How do i determine if the problem is with the FTDI chip (would the whole chip have been destroyed) or with other components?
I will also order another board, since i need this for a time limited project. But if I can fix it this would save me some time, since I have a bunch of FTDI chips laying around.
U1 is undoubtedly fried (yep, been there, done that). Replacing it should fix the board.
SparkFun does sell this chip for $3.95, PN COM-00650.
The hard part is soldering on the new part if you haven’t done much surface mount device soldering. The pin pitch is fairly fine. Look for other posts on soldering techniques.
I’ll suggest getting or building an RS232 level translation board. I’ve built a few and they do come in handy for connecting to a PC com port.
waltr:
U1 is undoubtedly fried (yep, been there, done that). Replacing it should fix the board.
Yeup, ordering one and think I have another at home. Done SMD before.
waltr:
I’ll suggest getting or building an RS232 level translation board. I’ve built a few and they do come in handy for connecting to a PC com port.
What did you use for the translation (which IC’s)? At some point I want to build some level converters + shift registers for making a generic flash programmer.
There are a number of newer ones that are better, they use smaller caps for their DC-DC converter. For most home building I like the DIP parts over surface mount since they are easy to wire up on a perf board.
SparkFun has the MAX2323 for a good price. This is a better MAX232.
SMD isn’t so dificult but when desoldering the broken chip you should be careful. The pads are very thin and easy to rip. I ripped one off entirely (bottom right corner of linked image). When cleaning the pads I ripped two others off that were both connected to ground (top left of image). To fix this I used a needle and scraped off part of the top layer to expose the contact layer that the now missing pad was connected to. Then in both cases I used a lot of solder (as can be seen in the photo) to extend the connection from the pins out to the new contact point.
When I removed the chip some of the other pads became elevated or flimsy, though they remained connected. Using the soldering Iron I gently flattened them back down to the service and made sure they were aligned properly to connect to the chip’s pins.
The soldering looks horrible but it works. I didn’t have the tools around to properly clean all the pads before resoldering and I didnt want to risk breaking another pad in the process. So I added no additional solder and just repressed the new chip into the old solder. I’m sure in the future I might run into problems because of this but for now, it works perfectly.](ImageShack - Best place for all of your image hosting and image sharing needs)
I use hot air and tweezers to desolder this type of thing. Pretty easy to remove without damaging tracks. How did you manage to desolder the chip if you didnt have a hot air tool?
MichaelN:
How did you manage to desolder the chip if you didnt have a hot air tool?
Add solder to all the pins on side 1 thereby bridging them together. In doing so the solder for all the pads on side one are melted at the same time. I had tweezers wedged under the chip and when side 1 was hot it slowly detached. I did the same to the other side and that was it. If I did it again I would be sure to apply less pressure with the tweezers.
I guess you didn’t need the verbose answer but just in case someone else tries this…
Well even if the operation wasn’t the cleanest at least the patient lived.
I’ve used the solder bridge all pins technique and it works most of the time. One trick is not to lift one side completely is one shot but lift a little then lift the other side a little. Keep going back and forth until the chip lifts off the pads.
Another method I’ve used to remove a chip like that is to carefully cut off all the pins at the plastic package with an Acto knife. Then with lots of solder remove the pins from the pads and soak up the excess solder with wick.
leon_heller:
I use Chip Quik for removing chips. It works very well and doesn’t damage the board.
Leon
Leon,
Although I like the use of Chip Quik to remove the chip. I hate the fact that the pads must be cleaned and new solder the put down.
I typically use lots of flux, and a hot air rework station. I just did some boot eeproms on some hard disk PCB’s. I didn’t use chip quik, for I didn’t want to try and get the right amount of solder back on them.
I just removed the chips, leveled out the solder, and put the new chips down.
It hard to align the new chip because of the solder “mounds”. But with tacky flux it can be done.
