Opties

Garmin 60CSx GPS - Wont turn on: LTC3456 no PWRON voltage? Next steps?

Hi I am pretty new to electronics repair and I am trying to fix my Garmin 60CSx handheld GPS. It was working fine powered up on a desk then it randomly died and did not turn back on. I have tried to check the power circuit but I have been stuck on where and what to check next?

An issue I noticed from my inspection of the Main power chip, an LTC3456, is that the PWRON pin and the RESET pin are not going high? According to the datasheet I believe the PWRON pin is meant to stay HIGH to keep the Chip on after the power button is released. When the button is held pressed down, everything seems to function normally around that area. All inductor voltages seem fine and stable. No capacitors appear to be shorted. But I get no signs of life on the device.

I am unsure where to move to next, would anyone have any suggestions on where to test next?

I think the bottom left section of the board photo is for communication so I have not tested there thoroughly.
The Crystals read correct Frequencies.
The CPU's gold pins on the topside of the chip had corroded and some are missing.
There was a general spread of blue corrosion on the board when it worked fine, which I cleaned with IPA %100.
The 2 wire jumpers are to supply power from a bench power supply.

I have an oscilloscope, multimeter, soldering iron and a hot air station.

Any help is greatly appreciated thank you.

Thank you.

Update 1:

I have finished testing around the CPU and RAM. From what I can tell everything seems fine?

All values are in the photo are for when the power button is pressed down. Anything that is not listed was either 0v or a floating/fluctuating low value from 0.1v-0.3

- Both crystals show frequencies.

- Most values are within 1.6v-3.3v

- Added a picture link of the CPU areas voltages.

LTC3456 Datasheet: https://www.analog.com/media/en/technica...

Power Circuits: