Corrosion on MB = No Calendar and No P1 Controller

[yo1dog]

Calendar settings would never keep even after replacing the battery. I found a lot of corrosion on the MB next to the controller board ribbon cable. Clearly someone had spilling something on the GC long ago. I hit it with some isopropyl alcohol and a toothbrush.

Here's before and after:



This seems to have caused R16 and C169 to break off. Now P1 controller port no longer works (P2, 3, and 4 do work).

Research revealed R16 is responsible for something to do with the battery and the clock/calendar settings. It was so corroded I assume that explains my initial issue. I also assume C169 is causing my controller issue.

Do you agree with my assumptions?
Does anyone have the specs for C169? I found R16 is 120ohm, but didn't find any schematics for the GC.
Recommendations on cleaning the remaining corrosion and rust?

I am electronics noob so, please, be gentle.

Thanks,
- Mike

[yo1dog]

Actually, looks like C169 is not supposed to be there... Hard to find a good image of the motherboard but I found this:

https://github.com/webhdx/PicoBoot/blob ... g?raw=true

[Extrems]

Yeah, the original schematic says it's not populated.

[novenary]

Short of using an ultrasonic cleaner, more scrubbing with a toothbrush or a q tip would be your best bet. You'll also want to rework those solder joints a bit (use flux liberally).

[yo1dog]

Fixed it! Funny enough, the problem had nothing to do with that big mess. It was the ribbon cable.

It just hit me that I remembered seeing slight discoloration on one of the ribbon traces. I found more corrosion in the ribbon connector. Cleaned that out and it works again.

Now to get my EE brother-in-law to replace that tiny 0402 resistor for me.

[yo1dog]

TL;DR:
C162 had gone bad as well. Removed it. Does anyone know the capacitance of C162?
The ribbon cable connector leg for the V+ trace was destroyed. I bypassed it by connecting directly to battery terminal.
Used through-hole instead of SMD to replace R16. Soldered directly to IPL chip.
Need to attach C162 replacement between resistor and ground.
-----

It's been quite a journey, but I think I have it fixed. Thanks in large part to this post by dilav and help from my brother-in-law.

First, we realized that the left-most leg of the ribbon cable was also destroyed by the corrosion. This connects V+ from the battery on the controller board. Failing to "fix" the leg by flooding the gap with solder, I decided to just connect directly to the battery terminal.


Then, being unable to solder the tiny 0402 footprint, I instead used a 120ohm through-hole resistor to replace R16... At least, I would have except I did not have any on hand so I used 6 of the 100ohm I did have. It's temporary I promise!


I connected one end to edge of C162 and the other to the V+ battery terminal on the controller board. This worked! For a few hours... The next day the calendar was broken again. The battery measured 0.22 volts...


V+ was shorted to ground causing the battery to drain quickly. I started mapping out traces looking for short.


I found that C162 measured only 5ohms across. Clearly that cap was also killed by the corrosion and causing the short. I removed C162 and this time attached the resistor directly to the IPL chip (this was much easier than soldering to edge of SMD).


Success! No more short to ground and calendar is still working days later.

I still need to replace C162. Should be easy to attach a through-hole cap between resistor and ground. Does anyone know the capacitance?

[Extrems]

1μF, 10V.

[yo1dog]

1μF, 10V.

Thanks! Much appreciated.