It would be a high short in this case, 0.2631k = 263Ω, which is again considerably different to what you were measuring earlier (grey) 0.35Ω
Can you give that inductor area a good scrub and provide me with a top down shot so i can see whats going on, I don’t have a lite board on hand atm… on first glance it would appear the short isn’t on the inductors output, which is potentially a good sign, but can’t say for sure atm without a closer look (eyeballing that diode in the shot)
Am not sure if I am on the right range setting but from what i understand this meter adjust automatically. Before I was on M. But the left pad kept looping around until I switched to K.
You don’t have to mess with the range button, the meter is auto ranging and it takes care of it for you.
can you put red probe on ground and black probe on the highlighted inductor pad.
It seems as though after you scrubbed this area your readings have changed, though it should be noted, i don’t know what constitutes a normal reading here as i don’t have a Lite board in order to test personally,the circuit is slightly different to a regular switch board a sit has that diode preset… do your other shorted rails measure the same or have they changed now too?
The two caps reading 103 now read 68 (both).
Cap reading 72.16 now reads 67.66.
Everything else same.
I’ve been informed by @tonike that on his Lite boards that he measures about 7k at the inductor relative to ground, standard polarity, though it’s to be noted that his boards have potential faults elsewhere.
On a regular switch board you’d expect to measure approx 200k or 10k depending on proble polarity.
What is your reading on the highlighted inductor pad reverse polarity (red ojn ground)?
So it looks as though your suffering a seperate fault on this primary SYS rail… or that the other faults are affecting it somehow.
Can you highlight these readings on a larger image, i can’t make them out in the attached image.
The thing that’s confusing me is the point in grey should be like for like the same as your inductor reading… can you check you have continuity from grey to the inductor pad that’s measuring approx 6K?
It seems your reading on the inductor is normal afaict.
Not much left from here in order to determine the culprit
On grey I was getting 0.5643 M(number jumping)but then it will settle at OL.
In continuity mode I am not getting a buzz but shows 75 Ohms but only on the northern side of the cap. Other side is OL.
On the other pad (ol) i get a buzz.
Actually i think I’ve made an error there, as the inductor is removed, you should be measuring continuity from the other pad to grey… so the high megs pad to grey should be close to zero ohms to grey
Yep I can confirm continuity on that pad to grey (buzzes).
So at the beginning you had a dead short on SYS (Large inductor by BQ) of approx 0.35Ω, then after heating the board your short seemed to change from a dead short to high (263Ω) and then finally you heated up and removed the large inductor and cleaned the area and your short appears to have cleared completely and you now have a reading of approx 6.764K which as far as we know constitutes a good reading. Which suggests you had corrosion in that area and the heat and subsequent cleaning solved it.
As the readings around the board seem to be changing so consderably, it’s possibly down to corrosion elsewhere, possibly under another IC.
Remove the SoC shield next i reckon just so we can inspect for any liquid corrosion, to remove the shield cleanly (assuming it’s the same style as a regular switch boards shield) put a scalpel/X-acto blade between the shield latches being careful not to scratch the board below, and gently twist the latch outwards so it’s no longer gripping the shield frame (don’t worry you can bend these latches back later) do this on all the latches and pop the shield off
Do you have a bench PSU by any chance?
Out of interest, what is your resistance measurments between rails, for example, one probe on red and another on purple… this might let us know if you have a bridge somewhere (which could be liquid)
Numbers jumping but around 0.278K Ohms.
Interesting I found a small cap[?] Out of place between memory and shield. Not obvious sign of corrison and didn’t like it was opened before.
Could this be the cause of the issue? I wonder how it moved as I didn’t apply heat anywhere near there. Unless previous owners did.
I’m in two minds as to whether the SoC has been reworked prior (flux residue) or if it’s just residue remains from the liquid damage…
Can you confirm if the two areas highlighted in red are solder debris? or is it just the lighting?
The area highlighted in blue is the most obvious liquid or flux residue visible, this wouldn’t be present on a stock board.
It’s likely not responsible for the faults, even so, i would still remove it for the time being.
Hmmm, no good.
I think what I’d do to begin with (assuming you don’t have an ultrasonic cleaner) is clean off the magority of the thermal paste then fill a tub up with IPA and submerge the entire board, use a toothbrush and give the board a good scrub (being more gentle around the SoC) … If you have any distilled or deionized water, then instead warm it up to about 60C and submerge the board in that instead and scrub, after dunk it in IPA for a bit and allow to dry.
Following the above, I’d surround the SoC and Ram with a good bead of flux and heat the board from the reverse side for a minute or two at initially 100C then step it up to about 180C for another min… I don’t like heating the SoC directly unless i plan on reworking it hence why from the opposing bottom which exposes the IC to less heat. You should see the flux bubbling away, add more if needed. afterwards repeat the cleaning steps from above again.
The fact that you have completely seperate rails shorted to one another might have already spelled the end for this SoC unfortunately though… for example 3V3PDR or 1V8PDR getting onto your lower 1VX rails