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Q103 -Q104 Short Repair Experience - YMMV

Thomas Valenti All Messages By This Member #111892 I am pretty far along in my QMX assembly now (the main board is finished). Sure enough, I had the dreaded Q103 - Q104 short circuit. I am lucky enough to have a hot air rework station, so I proceeded to follow the instructions in Hans' video to move Q103 a bit. Although YMMV, I believe that the best approach is NOT to try to nudge the device, but take it off the board altogether. When I touched Q103 it moved way too far anyway, and I could see that there was a solder bridge between the very close spaced traces. I am not sure that just moving the device a bit would clear that kind of bridge. So I took Q103 off, used solder wick to eliminate the bridge, and resoldered Q103 to the board with a regular soldering iron. You can only move the transistor a small amount anyway because otherwise it overhangs the edge of the board. With a fresh install, it is a lot easier to get it positioned properly. Tom K3AJ
Hans Summers All Messages By This Member #111900 Hello Tom, all I have cleared the fault on several hundred boards (since we now test for the fault before shipment, and fix any where the?fault occurs). You are right that just moving the device doesn't always clear the bridge. What I do in that case is nudge the large AOD403 (Q103) a little?CLOSER to the little BSS123 (Q104). Then nudge it further away again. This kind of "mops up" the solder bridge and surface tension takes care of it not forming again. So far, 100% success. It's a lot easier to do, than to describe. Even in my video it took under a minute, but I'm even faster now with more practice ;-) Since I have now finished necessary tests/repairs on all the Rev 1 PCBs I will now retire this [hopefully] unnecessary skill ;-)? 73 Hans G0UPL toggle quoted message Show quoted text On Mon, Oct 9, 2023 at 4:39?PM Thomas Valenti <tomk3aj@...> wrote: I am pretty far along in my QMX assembly now (the main board is finished). Sure enough, I had the dreaded Q103 - Q104 short circuit. I am lucky enough to have a hot air rework station, so I proceeded to follow the instructions in Hans' video to move Q103 a bit. Although YMMV, I believe that the best approach is NOT to try to nudge the device, but take it off the board altogether. When I touched Q103 it moved way too far anyway, and I could see that there was a solder bridge between the very close spaced traces. I am not sure that just moving the device a bit would clear that kind of bridge. So I took Q103 off, used solder wick to eliminate the bridge, and resoldered Q103 to the board with a regular soldering iron. You can only move the transistor a small amount anyway because otherwise it overhangs the edge of the board. With a fresh install, it is a lot easier to get it positioned properly. Tom K3AJ
David KO4EOD All Messages By This Member #115842 Well, today I was getting started with the build and discovered that I also have the Q103 short. I don't have a heat gun, so I'll try removing it, cleaning up a bit and reinstall the Q103 as you suggest. Wish me luck. Thanks for the tip!! Glad I checked this before starting the initial build steps, just incase I mess up the Q103 fix.... Cheers, KO4EOD

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