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Old 10-05-2021, 11:05 PM   #1
AJ847.63e
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Default 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Hi All,

Just wanted to see if I can get some advice on this 3437 I'm working on. It had extreme corrosion around the SSD and airport (WIFI) area. C3740 has both pads removed due to the corrosion, as R3742 and both sides are reading ground as I tried to revive the right pad and dug straight to gnd.

ISL was not pulling pin 1 to ground. Found R7105 was blown replaced it but ISL was still not pulling pin 1 to gnd. Replaced the ISL and that finally resolved that issue.

PP5VS5 was present as was PMSLP_S4L. Came back the next day and now the ISL is getting extremely hot when powering on. All the surrounding components seem fine. Noted down all the lines that go from the ISL but not surrounding components and started at pin 24 CHGR_UGATE which goes to Q7130. Checked pin 1 and it was reading 1 ohm. Checked my donor board and that was in the millions of ohm. Removed Q7130 but now it is still reading 1 ohm on pin 1. There aren't any other components on CHGR_UGATE. I'm going to continue down the list of rails that go from the ISL far away, but what else should I check for on CHGR_UGATE since according to my donor it's suppose to be far far from 1 ohm.

Thanks for your assistance!
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Old 10-06-2021, 01:38 AM   #2
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Replace charger IC and buck converter MOSFETs at the same time.
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Old 10-06-2021, 06:13 AM   #3
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Thanks Piernov. Just to confirm by charger IC you mean the ISL6259 U7100? I’ll have to order a new one if so, this is the second one I’ve tried and this was stolen from my only 3437 donor. This one seemed to work but it does look like the q7130 is also faulty which may be taking this new one out, and what took out the original and R7105. I do have another 820-00165 with its isl but it was corroded originally and the PCH looks like it has the slightest crack so not sure if I should risk using it or not. I just downloaded the data sheet so I’ll run through it see if some pin diode readings indicate whether it’s good or not. Otherwise hopefully digikey or someone locally here has them, international is a cluster ATM.

I do have another Q7130 on my 3437 but that has totally different markings to the one on this board. Are they interchangeable despite having different markings? How about the ones on the 165?

Thanks again!
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Old 10-06-2021, 06:17 AM   #4
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Forgot to mention I’m Really struggling to get the ISL joints on the left hand side (pin 1-7) looking shinny is that normal? When replacing the ISL I wicked the pads clean and they looked fine, but when re installing the new chip the left pins just looked horrible. Heat soak in the board or something? The other 3 corners are fine but man no matter what tip I use they just look like cold joints, even being liberal with flux and using the hot air and my big knife tip one and two come ok but the rest especially 5,6,7 look really bad.
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Old 10-13-2021, 12:20 AM   #5
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Ok U7100, C7125 and Q7130 have been replaced. Pin 1 on U7100 is now reading 330K ohm.

ISL is still getting really hot, and looks like R7105 is blown again. Not as much as before though, now it's only gone up to 70 ohm.Pin 1 on R7105 is reading OL. Replaced D7105 now pin 1 on R7105 was reading but I didn't note it down and now when I go to measure it jumps between .367M and OL. Diode mode just reads OL. Is there any other components on the 3437 or 165 that we can use as a temporary replacement for R7105? I've already stolen that exact resistor off both my 3437 and 165 donors and searching for a 20 ohm 603 resistor for both schematics came up with nothing.
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Old 10-15-2021, 08:30 AM   #6
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

100% sure charger IC is good, soldered properly, correct orientation?
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Old 10-19-2021, 06:18 AM   #7
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Yes orientation, (dot on the top left facing C7105) soldering looks good. I ended up replacing the ISL again, I was really struggling to get pins 1,2,3 looking nice and shinny. Once I replaced it the joints came out much nicer and now they all look good.

R7105 kept blowing. I believe that was because R7190 and R7191 were populated by the previous guy who tried to repair this. I removed them and replaced the TPS51980 as I saw the ever so slightest amount of green on the right side pins. Replaced both R and C7105 again and now the ISL is getting extremely hot. Q7130 seems ok, bit low at pin 1 is .135 diode mode but not as low as earlier. Nothing around the ISL is reading short. If I try to diode mode R7105 pin 2 or C7105 my meter just flickers between OL. Removed C7105 now it seems ok so that may of been the issue. Still getting extremely hot though I have not replaced C7105 yet as I've ran out of donors. Do you have to stick to the 50V? Surprised my iphone donors don't have any suitables.
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Old 10-19-2021, 07:06 AM   #8
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Quote:
Do you have to stick to the 50V?
No. Review the capacitor rail value and for safety, add 50% to the cap voltage. In fact, there are articles from a Maxim engineer that shows that the capacitance value is directly linked to the physical size & rated cap voltage.

That is, a cap that is 50v rated will not be the same capacitance (will be lower) than say a cap @ 12v rated if operating @ 12v or under.

So it is best to select a cap voltage close to but higher than the voltage for that rail.
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Old 10-19-2021, 07:47 AM   #9
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Awesome, thanks. I’ve been told I can leave it off for now just for testing so I’m going to do that. It and R7105 kept blowing so if I can remove a variable there it will make testing what keeps going wrong easier.

Is there any way to know whether the ISL is good or not without checking voltages? Do we have a pin out showing what diode modes on each of the pins should be? Did a quick google search hoping something would be on logi wiki but no such luck. I’m suspecting the isl is dead because R7290 and r7191 were not suppose to be installed and thus took out c/r7105 and likely the isl. but when I remove the isl and measure each pin to its ground pad it is not reading short so I’m not sure if it’s dead or not.
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Old 10-19-2021, 08:44 AM   #10
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Not following this thread but R7105 keeps blowing ? It should not, it is a low resistance resistor and this DC-DC convertor should not be consuming so much current to cause R7105 to blow / burn out.

Try the following,

1) Remove R7105 - the resistor BTW can be any low value (ie. 10-30 ohms). Effectively it is acting like a fuse if something is wrong with U7100.

2) Do not power up.

3) Meter in resistance mode, check the resistance to ground on:

a) D7105, pin # 3.

b) R7105, pin # 1.

c) R7105, pin # 2.

What are the resistance values for each ? Guessing that you have a short on R7105 to ground or U7100 is not soldered properly and is shorting this power rail, causing R7105 to burn out.

3) With R7105 off the board, what is the voltage @ D7105, pin # 3 when it is powered ? You should see the DC adapter input voltage here.
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Old 10-19-2021, 09:54 AM   #11
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

16V to VDD/VDDP of charger IC almost certainly killed it, they are rated for 7V max.
You should always disclose full history of the machine.
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Old 10-19-2021, 10:14 PM   #12
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Default Re: 820-3437-B No green light - Hot ISL - CHGR_UGATE Short

Thanks. I believe R and C were blowing because R7190 and R7191 were installed when they shoudn't of been. I removed both and R7105 stopped blowing but I think the damage was already done and as Piernov said probably killed the ISL.

I'm currently using a 5 ohm resistor for R7105 closest value I have. C7105 is off the board. Removed R7105 and resistance on pin 1 is 160K D7105 pin 3 is same. Pin 2 of R7105 is OL. With the ISL in place. Removed the ISL but pin 2 of R7105 is still reading OL. With R7105 removed D7103 pin 3 is getting DC in voltage. I'm suspecting R7190 was the issue all along. Gotta wait for my new ISLs to arrive and hopefully that will work.
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