**** BEGIN LOGGING AT Sat Jan 01 02:59:56 2022 Jan 01 16:13:47 Looking at page 4 of N900 schematics, and testing my broken USB n900, where the USB Vcc/Vbus pin shows a short to ground Jan 01 16:14:39 The curious thing is, there's no such short to ground when I put multimeter on F5300 Jan 01 16:17:42 F5300 itself isn't blown. Now I'm wondering - can I 'safely' ignore the mysterious short to ground on the actual usb pad and instead solder a new port's vbus pin to F5300? Unless I'm missing something here, at least schematic and my F5300 findings suggest it should be safe Jan 01 16:17:59 joerg, and others, ^ Jan 01 16:19:20 how did you detect that "short"? Jan 01 16:19:55 and where's my N900 schematics? Jan 01 16:24:58 If i place multimeter on pads that correspond to 1 and 5 on microusb, it shows continuity Jan 01 16:26:07 well, that's what is supposed to happen since this is a power-in rail, no? :-) Jan 01 16:26:33 There was a previous failed attempt to re-solder the usb port back on. That said, I really can't understand how it could lead to this short, and more weirdly,why it isn't 'visible' on f5300 Jan 01 16:27:05 measure true ohms Jan 01 16:27:18 Hehe, well, if i place dmm on 1 and ground, i have continuity. Exactly same thing with pin 5 and gnd Jan 01 16:27:24 Wi test ohms now Jan 01 16:27:34 or duh, just connect a USB charger and measure voltage from F5300 to GND Jan 01 16:29:31 True ohms between 1 & 5 is exactly 0 Jan 01 16:31:04 Found your schematics? Jan 01 16:39:34 sure :-) Jan 01 16:40:20 you say you don't find that short from F5300 to GND? smells like a failure in probing Jan 01 16:41:10 or you soldered VBUS pin to ... sleeve? instead of PCB pad Jan 01 16:44:00 measure ohms between both sides of F5300. When you are confident to always get a proper contact and instant result (~0 ... 1 ohms), measure again F5300 (either side) to GND or pin2 of batt connector Jan 01 16:44:43 New port isn't soldered in yet ... i won't do it right away Jan 01 16:46:35 so what is it you're measuring? USB PCB pad to F5300? Jan 01 16:47:13 an what's >>between 1 & 5< Usb pad 1 and pad 5 Jan 01 16:51:04 according to schematics there is absolutely nothing other than a plain simple trace from VBUS pad of USB socket footprint to F5300. I don't see how that could possibly have a short to GND at one end and none one the other Jan 01 16:51:17 Yes, beats me Jan 01 16:52:48 there must be a glitch in probing somewhere Jan 01 16:53:11 measure continuity from pad to F5300 Jan 01 16:53:28 what means >>F5300 itself isn't blown< Pad to f5300 = 47kOhm Jan 01 16:56:01 F5300 not blown means i get 0 ohm when dmm leads are on each side of f5300 Jan 01 16:57:13 you actually managed to damage PCB so the trace from USB,pin1 to F5300 is cut and instead shorted to GND. Congrats :-) Jan 01 16:57:42 :-p Jan 01 16:59:04 you of course can connect USB receptacle pin1 VBUS "free air" yellow wire to "right hand" pin of F5300. Make sure the receptacle pin1 does never touch the PCB footprint pad Jan 01 16:59:41 Right hand pin of f5300 means? Jan 01 16:59:51 however carefully check the other 4 footprint pads before you proceed Jan 01 17:00:15 "right hand" in schematics, the one supposed to connect to USB Jan 01 17:00:53 the fuse can't be 0 Ohms, must be at least fraction of an Ohm Jan 01 17:00:54 D+, D- are intact. Continuity seems okay. Only the vbus is borked Jan 01 17:01:07 0.5ohm Jan 01 17:01:12 check for short to GND too Jan 01 17:01:22 on D+- Jan 01 17:01:49 I did. They're okay Jan 01 17:02:31 0.5R sounds absolutely correct. So you can determine which end of Fuse is real 0 ohms to N|L|C 5300 Jan 01 17:03:13 to the other end you may solder some thin wire and run that to the "aired" pin1 of receptacle Jan 01 17:03:25 NLC means? :-) Jan 01 17:04:04 N5300 diode, L5300 coil, Capacitor Jan 01 17:04:21 Right. Let me locate those Jan 01 17:04:38 C5300 is a 4pin capacitor, prolly looks odd Jan 01 17:05:41 N5300 diode also looks like it's supposed to be 4pin Jan 01 17:09:21 Yes, so i can't probe that. Even the cap is a weird 4 pin thing :-p Jan 01 17:09:52 At least all are accessible. The diode's pins are underneath (balled is the term?) Jan 01 17:10:41 sicelo: the capacitor like the diode have 2 connected pins that are VBUS and 2 connected that are GND Jan 01 17:11:08 BGA package, yes Jan 01 17:11:27 I guess my T235H dmm's resolution isn't the most accurate around. But looks like the vbus side of f5300 is the one on left when camera module is on top Jan 01 17:13:46 can't duplicate that now. you could send a 1A current through the "short" from F5300 to L5300 and measure the voltage across F5300. If there are something like 0.5V its ok, if there's 0.00V then you feed the current to the wrong side of F5300 Jan 01 17:15:27 Makes sense. I'll try that Jan 01 17:26:58 when you use a lab PSU, watch out for damn output buffer capacitors that defeat current limit completely for a curent surge on making contact! Jan 01 17:30:48 keeping that probelm in mind, you may just get away with two tips and lab PSU: adjust current limit to a few 100mA; connect L5300 and "wrong" (L5300) side of F5300; ramp up voltage until PSU signals current limited mode, add a 50 or 100mV on top ; now switch off PSU and short output to discharge buffer capacitor inside PSU; connect to "right side" of F5300 and L5300 and switch on PSU, current limit shouldn't kick in thanks to the 0.5R of fuse you have now in Jan 01 17:30:50 current path Jan 01 17:34:49 Unfortunately I don't have it (lab psu) Jan 01 17:35:05 But can do that test later at a friend's Jan 01 17:41:50 good luck! Jan 01 17:42:09 and happy new year, better than damn 2021 Jan 01 17:42:17 to all of you Jan 01 17:43:13 *sigh* topic is vasty meaningless without infobot :-/ Jan 01 17:46:19 maybe I could find infobot factoids for ~lf (or ~tabletsdev ~combined ~emmc ~flasher) sdk: ~sb in my chanlogs and set up an autoresponder for them Jan 01 17:48:37 http://reisenweber.net/irclogs/libera/_maemo/_maemo.2021-01-17.log.html#t2021-01-17T13:24:06 etc **** ENDING LOGGING AT Sun Jan 02 02:59:56 2022