Hi all,
just wanted to let you know that I had some interesting experiences recently. It started with a shock when once again I had done SMD capacitor replacement on multiple SB3s and the dropout rate was extreme. Five separate devices, all would boot but crash and reboot once they were commanded to start playback. Three of them "died" somewhere between the moment I detached the CPU board to do the capacitor replacement and the moment I put it back together to test. Three! They would do what every dead SB3 does, show a very dim TOSLINK, no connectivity, no display. And that despite the fact I hardly ever touched the CPU board at all. I still can't explain how it got to this three times in a row (even five times in a row earlier which had me so depressed I would almost quit). I wore a grounding wrist strap all the time. I discharged the capacitors before replugging the CPU board. Used current limiting for the first startup to ensure that a short won't blow anything up. Used an IR camera to look for hotspots during powerup. So that was a bit awkward. The devices were sent to me for repair and shortly after the repair they would fail and be much worse than they initially were. One of them had run a firmware update, then restarted and was normal for a short period of time before it failed. Which brought me to an idea. Just out of curiosity I extracted the Flash EEPROM from one of them and put it in my reader. Compared to a known-working SB3 there were a lot of differences, at least in the first blocks and, expectedly, where the configuration is held. But I would not assume that the bootloader or whatever is read first from the Flash is very different between identical devices. So I attempted to flash the working image to the EEPROM that was suspected corrupt, with erase first and eventual verification of course to ensure that it isn't the chip itself that is at fault. Then soldered the chip back in and, what do you know, two out of three SB3s were recovered! A Boom PCB is under repair currently, I'll try the same thing there as the hardware arrangement around the CPU is similar to that of the SB3. It looks like what I used to call "CPU death" actually isn't the CPU but the Flash memory for some reason. I don't know why it happens. It should only be written to during configuration and during firmware updates, but something during the repair seems to cause a partial corruption. It's a pity that the EEPROM needs to be desoldered and put back in place as this can only be done once or twice before the board gets damaged. But it's way better than attempting to reflow the CPU which I never succeeded at, and most of the time it might not even be the component at fault. The EEPROM is not easy to handle thanks to its 0.5mm (or so) pin pitch but way easier than the BGA stuff under the CPU. I have too little experience yet to document this or proclaim it as one of the first measures to fix, and due to the complexity of the operation it should rather be considered a last stand, but still. There is a lot of new hope for the stack of failed SB3s and Booms I have around, and I'll let you know how I fare with it. Cheers, Joe PN me if your Boom / Classic / Transporter display has issues! Blog: https://www.blogger.com/blogger.g?rinli=1&pli=1&blogID=5053304027701850753#allposts ------------------------------------------------------------------------ JoeMuc2009's Profile: http://forums.slimdevices.com/member.php?userid=23131 View this thread: http://forums.slimdevices.com/showthread.php?t=117140 _______________________________________________ discuss mailing list [email protected] http://lists.slimdevices.com/mailman/listinfo/discuss
