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820-01700 no backlight + other issues
- Thread starter nininunz
- Start date
What is the exact resistance to ground on PPBUS_G3H?
Compare with values on all big coils; including L9080/580.
Compare with values on all big coils; including L9080/580.
nininunz
Member
What am I comparing on L9080? Like PP2V5_NAND_SSD1 to ground? to ppbus_g3h? to PP2V5_SW1_TPS62180_SSD1? Sorry for my ignorance.
ppbus_g3h to ground when I first touch its about 5ohms then drops to 3ohms after 2-3 seconds then settles around 2.5ohms, but when I hold it a long time (20+ seconds) it keeps creeping down, got down to 1.9 before I got too impatient after about a min.
ppbus_g3h to ground when I first touch its about 5ohms then drops to 3ohms after 2-3 seconds then settles around 2.5ohms, but when I hold it a long time (20+ seconds) it keeps creeping down, got down to 1.9 before I got too impatient after about a min.
Allow 10-15s once power is removed, before checking in diode mode, or ohm scale, on any power rail.
Considering 3 ohm to ground at PPBUS_G3H and apñrox same reading on L9080 (or any other coil), you have two options when testing between PPBUS_G3H and L9080 (or other coil), in ohm scale: 6 ohm, or 0 ohm.
In other words, you will get the sum, or difference of the readings to ground.
If you get the reeadings difference , which can be 0 ohm in this example, then you have a short between PPBUS_G3H and corresponding coil.
It can be caused only by the power chip connected between both rails; an high-side MOSFET, or power IC.
In case of very low reading on a coil, you can also compare with good board.
3 ohm on L9080/580 is very bad; short for sure and damaged power IC, NAND chips, or filter capacitors.
However, CPU/GPU coils have very low resistance as normal.
Considering 3 ohm to ground at PPBUS_G3H and apñrox same reading on L9080 (or any other coil), you have two options when testing between PPBUS_G3H and L9080 (or other coil), in ohm scale: 6 ohm, or 0 ohm.
In other words, you will get the sum, or difference of the readings to ground.
If you get the reeadings difference , which can be 0 ohm in this example, then you have a short between PPBUS_G3H and corresponding coil.
It can be caused only by the power chip connected between both rails; an high-side MOSFET, or power IC.
In case of very low reading on a coil, you can also compare with good board.
3 ohm on L9080/580 is very bad; short for sure and damaged power IC, NAND chips, or filter capacitors.
However, CPU/GPU coils have very low resistance as normal.
nininunz
Member
This is minutes after power is disconnected. It will do this every time I check.
Diode mode between ppbus_g3h and L9080/580 is both .460
My thought was the short could be a mosfet because there was no discernible heat coming from anywhere on the board.
Sorry, I don't understand what you mean. Mind explaining?
nininunz
Member
I'm an idiot, I really do apologize for wasting your time. A jumper I ran some time ago came loose when I was cleaning corrosion in the area and it seems I soldered it one pad over from where it should've been, a ground pad :|
Now to tackle yet another issue I created on this board. Some components by U4900 and U4920 blew away when I was removing U4920 to clean up a corrosive mess.
Now to tackle yet another issue I created on this board. Some components by U4900 and U4920 blew away when I was removing U4920 to clean up a corrosive mess.
0.1 ohm shouldn't be through an high-side MOSFET, or power IC.
However, check first if you don't exact same short on any coil; don't forget L9080/580.
If none of them gives such short, then is safe to inject voltage into PPBUS_G3H.
Anyway, start with 1V and slowly increase if needed.
Set amp current to max first.
However, check first if you don't exact same short on any coil; don't forget L9080/580.
If none of them gives such short, then is safe to inject voltage into PPBUS_G3H.
Anyway, start with 1V and slowly increase if needed.
Set amp current to max first.