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Kamcio · 01-27-2026, 11:04 AM

So I desoldered PC1942, PR1931 and PR1935.
As in attached image - on pads #2 on both resistors there is 0ohm. On pads #1 on both resistors I have 70k.
Desoldered ISL - now i have 0 ohm there. So once again chip was probably faulty. I assume it was faulty, because I was really careful with positioning it before soldering it to the board so there shouldn't be problem with bridges etc.
I'm afraid I'm out of these chips for now and package from Ali didn't arrive yet...

Kamcio · 01-26-2026, 02:37 AM

Full path resistance - do I understand it correctly as a resistance between pin 1 and 2 of the IC? If yes, then there are 575k ohms.
PQ1900:
s/d - 120k and rising
s/g - 530k and rising
g/d - 219k const
PQ1901:
s/d - 112k and slowly rising
s/g - 470k and slowly rising
g/d -35k and slowly rising
PQ1902:
s/d - 150k and rising
s/g - 150k and rising
g/d - 225k const
PQ1903:
s/d - 110k const
s/g - 1.25mega const
g/d - 710k const
PQ1904:
s/d - 110k const
s/g - 1.04mega const
g/d - 680k...

Kamcio · 01-24-2026, 01:52 PM

CSIN, CSIP - both 19v
PL1901 - 0v

Kamcio · 01-24-2026, 12:35 PM

Okay, I have ordered 0603 and 0402 caps and resistors set, aaaaand some spare ISL chips on Ali

Meanwhile for testing I have changed these low ohm resistors to just a wire since room there is quite tight for 0805 -> 2.2ohm PR1914 (BOOT2), 2.2ohm PR1905 (BOOT1), 4.7ohm PR1908 (as You suggested above, VDDP), 1ohm PR1901 (CSIP) and 1ohm P1902 (CSIN). One of these last two measured megaohms and was dropping 19v to 18.x even when there was 19v before. Maybe heat cycling broke it.

ACOK is now 3v!
There is also 5v on COMP, 2.8 on VBAT (was 4v before), but both BOOT1...

Kamcio · 01-24-2026, 07:03 AM

It has 5v on both sides. Both also shows ~80k ohm to ground. 10k Between pads. I see there should be 4.7 ohm.
I should have bought 0603 and 0402 cap and resistor set

Kamcio · 01-24-2026, 05:39 AM

Around 70k ohms on board
100k with resistor pulled out from the board

Kamcio · 01-23-2026, 03:49 PM

0.80v...

Kamcio · 01-23-2026, 12:48 PM

0v, unfortunately

Kamcio · 01-23-2026, 11:26 AM

From what I understand, low side mosfets are PQ1903 and PQ1904 and they are opened respectively by LG1 and LG2. There is nothing on these gates.
But I have good news - after replacing 0ohm resistor, there are more voltages on the ISL chip -> in attachment.
I've also replaced 2.2ohm resistors PR1905 on BOOT1 and PR1914 on BOOT2 because they had megaohms instead....

Kamcio · 01-23-2026, 08:13 AM

Alright, I've replaced PR1903 with another 0ohm resistor. Haven't powered the board on yet.
Now for whatever reason PL1901 reads 6 ohms to ground. I had that before when I touched gates on either PQ1900 or PQ1902 with beep mode. Problably opened these mosfets since beep mode sends some voltage to gates, ahh.
Schematics looks like 100% matched, at least components around ISL.
Attached pic has 000 resistor which is PR1903 - directly connected to ADP pin in ISL on one side....

Kamcio · 01-23-2026, 06:24 AM

PR1903 - doesn't look like cracked, blown or discolored.
Resistances:
GND to SDC_IN pad -> 80k and rising
GND to ADP pad -> 600k const
Between 2 resistor pads - 500k and rising

PL1901 - no voltage at all on both sides

Kamcio · 01-23-2026, 04:30 AM

VCC: I haven't found this particular name on my schematics. There are DCIN pin17 19v, VDD pin18 0v, VDDP pin8 0v, ADP 0.3v
ACIN: 3.59v
ACOK: 0.02v...

Kamcio · 01-23-2026, 01:19 AM

Thank You for reply!
PQ1901 drain to GND started from 50k ohms and was rising when probed longer.

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Dell Precision 5540 - LA-H33, EDP51 - ISL chip not starting