I checked resistance on 2R2 and got a moving figure from around 10k up to 900k
I replaced the M92 and BQ chip and have charging at 15v 0.48a but not fast charge but this is with a RavPower USB supply not original so don’t know if that’s the reason.
It did not boot but does go into RCM Mode. I am not sure to be honest if I have mixed up the Nand or not .
Injecting Biskeydump i got backlight but no display. Injecting Heckate.bin I got backlight then near the 8316ic a capacitor started smoking so I turned it off and disconnected the battery - see pic, the small cap in the middle
We can verify this once you’ve got the LCD shpwing a display using biskeydump (or other) though if you have mixed/matched the EMMC from another board there is a 50/50 chance you’ve blown the update fuse on the CPU which will require further steps later on
Can you highlight the capacitor in question so I can see which rail this is on? as afaict the small one in the middle would be VIN (SYS rail) which you previously didn’t measure a short on, I would measure the resistance across the capacitor and note the reading, if it’s shorted, remove the cap then measure across the pads and see if it’s cleared, though this will depend on the rail in question but provided the short is clear, then likely it’s not the IC at fault If it’s not short though, then as Insomniac said, it’s likely the IC at fault, and I would replace it with another.
Without taking the capacitor off get 50ohms measuring from either side of it and no short to ground on one side - circled but the black component arrowed is now shorting to ground
Yeah, the highlighted cap is on the SYS rail which we already know is not shorted to ground, so it almost certainly is the IC at fault and/or an issue with your reball, though I would replace the capactor as a matter of course if it was getting hot
Think your meter/leads are playing silly buggers with your here, this is a bypass cap, one side is ground, so you should be measuring a near dead short here on one side of it.
On my board with Ram issue, the black component with he arrow pointing to it is OL both sides and gets 175k resistance to ground on both sides and diode reading of 540. on this board I get 5ohms resistance to ground and diode reading of 0v.
Also my other readings dont match the post by @jkyoho so it does look like I did not do a good job on the 8316 IC. Its a bugger as that is the 4th time I have tried that IC. Got 5 new pre-balled ones from RS Components and have 1 left. Was sure it was on right this time unless there could be something else causing them to blow each time? Would be nice to think I got it on right at least one time
Going to take it off again and recheck readings without it to see if they are back to normal before trying to put my last one back on
I haven’t checked, but that sounds about right, the black component is an inductor btw
Yeah, that’s no good, I’d pull the IC and see if that 5 ohm short to ground disappears
Ahh I didn’t realise you’d went through so many of them, I would verify the resistance to ground on the +/- 5V outputs at the 8316 IC when the chip is removed and also measure directly across those two diodes (using the nearest neighbour components/pads) in resistance to determine if they are shorted, while it’s possible a shorted diode could blow the 8316 IC it’s not actually that common but worth checking. The other possibility is bridges at the LCD connector pins/joints, I think you said you already verified this but worth double checking too
Most important thing is checking those above measurements prior to attaching battery/power to the board when you’ve put the replacment on, the chip won’t blow if you don’t power it up
@Severence Sound advice thank you, will give this all a go tonight if I get chance, if not tomorrow and report back, thanks again for all the replies, will not let this switch beat me lol. Only doing it for the fun and to see if I can, while improving my soldering and diagnosis skills so wouldn’t be a challenge if it was easy
So took the IC off and get OL on most readings but assume that’s because the chip links the components and without it there is not path??
Resistance to ground on the +5v is 90kohm and -5v is 0.3kohm but that may be right as it links straight to ground if I’m not mistaken.
I am getting a normal reading now on the inductor but low diode reading of 0.134v drop on the +5v diode and OL both ways on the -5v diode - it doesn’t look very good. Resistance over the +5v one way is 6.5kom, the other way is 1.8kohm, the -5v diode is 295kohm both ways. Do you know what diodes these are or can be replaced with?
Seems a little high in one orientation, I measure approx 480 ohm across this in one polarity (though worth noting that the bare die versions of this diode which your board doesn’t use measure approx 4K in one polarity) and an effective fluctuating open in the other, perhaps meter differences at play here… what diode mode reading do you get across this diode in both polarities?
This diode has blown open by the sounds of it
I don’t tbh I usually just pull them off donors usually
I’d verify the size of the diode package with some calipers though first just to be sure.
Provided the specifications are a close match, will be fine as a replacement, though I don’t imagine either of these rails draw anywhere near 1A max, you could probably go lower if you wanted worst case
yeah saw that but down as not recommended anymore and not in stock, the alternative that is recommended is RSX101VAM30 but that is slightly larger than the one I found and the shipping costs are too much compared to the part price and size. Do you thing the ones on RS look ok for the purpose?
Suppose if you wanna do a mouser order and get the order price up for the free shipping then here are some things I’d pick up
a roll of 63/37 Chipquik solder
If your planning on continuing to work on Switch boards, grab some fuel gauages
some more 8316 IC’s just incase
your diodes
That should bring your order up to about the limit if you wanna go the Mouser route
That’s good, likely means the chip hasn’t blown up this time
Can you clarify, do you mean volts? as if you mean mA and you have your meter in the current/amps mode you’d effectively be shorting it out measuring in this fashion
if you mean volts, disconnect batter/power and make sure the negative rail diode isn’t open again, and if it isn’t make sure it’s on the right way round, after this has been verified, check to see if your getting your 1.8V enable present for the -5V rail (there is two of them)
Getting 1.8v on both the 2 leftmost pads to the IC
on the diode i get .14 one way and 1.5 the other which matches my boards that displays but has a ram issue. Assuming as one side is tied to ground from the coil?
