820-4924 Short On PP3V3_S5

[KootenayMacGuy]

Hi there.

I have a board here that had a small amount of liquid around the keyboard backlight connector causing it to randomly shut off. I repaired the corrosion as well as some bad traces arounf this connector, then tested for any shorts. I then cleaned the board with my ultrasonic cleaner. After complete dry and reassembly, I now have a direct short to ground (2ohm @ 6A) on PP3V3_S5 line. I have attempted to find the short by running 3V to the line on the board (at C7592) and then spraying alcohol, but I cannot see it or feel it. Where do I go from here?

 

[2informaticos]

"2ohm @ 6A"
What this means???
Post exact resistance to ground (ohm scale).

 

[KootenayMacGuy]

Sorry. 0.2Ohms short to ground on PP3V3_S5. Power supply uses 6A@3V injecting into that line.

 

[2informaticos]

I doubt you've injected 3V/6A; that means 18W, something MUST heat seriously.
If your PSU got in protection mode, didn't inject anything.

"Start injecting with 1V and increase slowly, if needed; do not exceed 4V.
Set amp limit to max on the PSU first."
This post is 3 hours old...

820-01598 no power

Arrived with liquid damage primarily in U6903 area. Replaced U6903 and all affected components. When turned on PP3V3_G3H and PPBUS_G3H are fluctuating drastically including CHGR_EN_MVR. stuck at 5V on charger. What should be checked next?

boards.rossmanngroup.com

We discussed so many times how to inject voltage, on the forum.
I can't beleieve that you didn't catch any of these threads.
Maybe you didn't consider to be an intersting information to save it...

 

[KootenayMacGuy]

Perhaps I need a new Power Supply? Its working fine otherwise...

 

[2informaticos]

Is that 5A power supply.
If yes, doesn't serve for voltage injection.
You can find few links in the forum, about 20A adjustable power supplies.

The pictured setting injects only 4.3W, not easy to detect; if PSU is not already in protection mode.

 

[KootenayMacGuy]

Thank you for the help. The DPS5020 on eBay looks like a great choice. This is a DC-DC power supply however. Can you recommend an AC-DC power supply that I can connect to this so I can use it?

 

[2informaticos]

This kind of PSU is not easy to manipulate.

I prefer 20A version, with analog settings.

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Be sure to get correct 110/220V AC.

BTW, adjusting current output is not a need for voltage injection.