iPhone 6S Short on VCC-Main

[LastDeuS]

Well guys this almost never happens but this customer returned but this time for data recovery and this time I tried at 1A for a while but could not see heat again waited a couple of minutes before raising the Amps and when I got to 5amps and left it there for a couple of seconds I found the short at C2126

Ok As jessa always says patience is very important, I used my same wire but this time I soldered to 2 caps at the same time which shouldn't have made any difference but there was significantly less heat in the area were the wire was soldered.
Also as you all recommended the ground point should be larger so I just used clamps onto a screw hole and there was almost 0 heat on that point so it was easier to find small amounts of heat in the areas nearby

so thanks again to everyone that helped finding this solution

[crea2k]

You don't, I just use mine for other things too so have a powerful one. One thing I found though as with a lot of Chinese stuff is they never give the rated current, so my supposedly 5amp supply is totally useless for short finding as it flakes out before anything gets slightly warm. The other one does a far better job. The idea is not to smoke the traces you are injection into though or you're asking for more problems. That's why I inject and remove and look for what's melted.

[Jessa_the_Professa]

Just want to clear up how DC power supplies work for short detection.
1–finding a short with heat is just a tool. Don’t obsess over Finding heat—it is not a crystal ball. Many times when you do find heat that is not the cause of the short anyway. Check for heat for a few minutes then move on. History, experience, visual exam, and random guessing can also combine to find the cause of a short.

2–any cheap dcps is fine for finding shorts by heat. Most of them will not let themselves catch on fire so they limit current. If you set a voltage to X, and then connect black and red together creating a full low resistance short, then the dips will automatically drop the voltage in order to limit the current to an amount that will not catch it on fire. Raising the voltage does nothing—a full short will consume a huge current so the device will smartly lower the voltage to protect itself! This is a good thing.

3–you can manually adjust the current limit within a range by shorting the leads together. I limit the current to about 2A for iPhones. My cheap DCPS will allow me to work within a range of current limit from 0-5A. I almost never go above 2A, and can’t possibly imagine a use for cell phone repair to need more than 5A. Any cheap dcps is fine for cell phone repair. The simpler the better!

[eDigitCom]

crea2k Why would you need a power supply that can supply 20A for iPhones?? Is there a need for it?? That 600W

Is it Switch Mode Power supply

[eDigitCom]

I be afraid to put more then an 1A into an iPhone. has II see when it powers up at 0.6 A and may go to 0.9A with a 3.9V Jessa when you say you not go above 2.5A would this be with a voltage of 3.9V. To go to 5A I be thinking the phone would blow UP UP and UP

[crea2k]

That's the big one I have, simple and cheap

https://m.alibaba.com/product/60371002464/LONGWEI-INSTRUMENTS-0-30V-0-20A.html

[crea2k]

Lw-3010 kd is the one I have that works, the other one is fine for supplying power but useless for short finding. The 3010 sparks like an arc welder if you touch the leads lol.

[LastDeuS]

I think it depends on the type of power supply, trying to think which YouTube channel I was watching the other day that explained it better. For example iv got two different ones, one is next to useless for short finding, as if I put a zero ohm short on it, all the red lights come on and it limits the voltage and current, where as my other one is really good, it'll just keep blasting it in until either the board blows up (never a good idea) or the power supply starts to get hot. I only try to hold the probes on for a few seconds though as the big one can chuck in 10 amps if it wants to which is major overkill.

Yeah that's exactly what happens with mine it shows a cc red sign and voltage goes to 0 so I know it's not good for this kind of shorts but one the facebook group there is a post about this where people talked about Short Spy DCPS which go up to 30A not sure if this is even a good idea but still the guy seemed to love it for this kind of shorts even if never shared where he got it

I do feel like I should maybe get a different one where you can disable the protection or maybe comes unprotected

[crea2k]

I think it depends on the type of power supply, trying to think which YouTube channel I was watching the other day that explained it better. For example iv got two different ones, one is next to useless for short finding, as if I put a zero ohm short on it, all the red lights come on and it limits the voltage and current, where as my other one is really good, it'll just keep blasting it in until either the board blows up (never a good idea) or the power supply starts to get hot. I only try to hold the probes on for a few seconds though as the big one can chuck in 10 amps if it wants to which is major overkill.

[LastDeuS]

Zero ohm / low on shorts are way easier to find with low voltage and freeze spray anyway. As if you go blasting 4 volts into it and your power supply doesn't have a current knob like mine you end up blasting 10 amps into the board which isn't ever a good idea, plus the board heats up that fart you can't see what heated up. Il start at like 1 volt or something and work my way up if it's a higher voltage line. I deal with a lot of water damaged boards so most of my shorts are total phone dead zero ohm ones so easy to find with 1 volt and freeze spray.

This kind of short makes no difference the Voltage I choose on DCPS even if at 4V when connected to the board the voltage dropped to 0.3V for 1A and if you increase the Amps to 2A then goes 1.1V and so on

[LastDeuS]

I always use only up to 1A to search for the heat and rarely go to 2A if I cannot find anything in this case I used 5A on the video because that was the last attempt to make the culprit burn if possible but not even at 1A and patience could find anything and as usual my customers cannot wait over 3days lol so had to let this one go
thanks anyways for the help Jessa and crea2k

[crea2k]

Zero ohm / low on shorts are way easier to find with low voltage and freeze spray anyway. As if you go blasting 4 volts into it and your power supply doesn't have a current knob like mine you end up blasting 10 amps into the board which isn't ever a good idea, plus the board heats up that fart you can't see what heated up. Il start at like 1 volt or something and work my way up if it's a higher voltage line. I deal with a lot of water damaged boards so most of my shorts are total phone dead zero ohm ones so easy to find with 1 volt and freeze spray.

[Jessa_the_Professa]

I watched your video. You have too much heat. Turn the current limit down so that you give the board a chance to let the heat from the component declare itself.

[Jessa_the_Professa]

Current is not pushed—voltage is pushed, current is consumed. I almost never go above 2.5A.
i would solder a thick wire and not use anything fine if you are looking for heat.

[LastDeuS]

If the heat is spreading from your ground contact you need a bigger ground contact. I made this mistake when I started trying to do voltage injection and used to solder wires on the board. Now I just either user a crocodile clip for ground and old multimeter probe to inject the power or just two mulitimeter probes, as I found like you that the ground wire always got stupidly hot. Presumably because we are trying to force so much current through a tiny wire, or the connection is poor to the board. I just clip onto a screw hole or shield with the clip and probe with the other end. It's probably safer this way too as you can immediately remove the power probe.

I do not use a wire for the ground contact but a needle with a slightly round tip I'm not sure if it can be seen on the video but you think I need something bigger? it's actually bigger than my probes which are super fine

Also how much current can you push with your old multi-meter? I saw someone on the group mention they used even more than 10 amps sometimes to find the short but my multi-meter is the same one jessa recommends only goes to 5A