Today as I was working in the car I just happened to find a remote and key buried deep in the dark recesses. It looked so sad and grimy. The poor thing looked like it had been there for years and judging from the other hidden items found with it dating to 2007 it had been at least that long since seeing the light of day and it's owners gentle caress.. I wish I would have taken pictures but alas I was not thinking about it. Anyway, I decided to give it a go and see if I could get it to work.

First off was to get the battery door open. Now instructions were excellent but the poor thing was so glued together with who knows what had been spilled in it's hiding spot that the case separated instead. As I looked at the circuit board within, to say it was in deplorable shape was an understatement. The board was covered with what can best be described as fossilized coffee and soda along with some green corrosion. So out comes the 99% Isopropyl alcohol (IA) and cotton swabs and clean up begins.

First off was back to getting the battery door open. Generous amounts of IA, a few swabs and gentle prising of the battery door finally got the crust to break its hold. Inside I found what once passed for batteries (2-CR2016) Giving the batteries a good going over with IA and swabs I was able to get them to break free and slide out. A careful cleaning of the battery contacts with IA and amazingly they cleaned up rather well. At this point I asked my self "Do I install new batteries or delve further?" I decided to err to caution and take the remote further apart for proper inspection and cleansing.

Now among my many hobbies and jobs over the years I have always enjoyed electronics. So I break out my electronic rework kit comprising of a de-soldering/soldering/SMD station, my small circuit board vice/stand and my digital microscope stand I made. A little research online gave me the information I needed to separate the board from the FOB case. The only thing holding the board in are the tab and ring for the batteries. First one to come out is the (+) tab. It must come out to get proper access to the (-) ring. You must be very gentle doing this as the pins for those are quite slender. Once they had been de-soldered and removed a thorough cleaning with IA and swabs allowed me to remove the circuit board.

As I suspected, the hidden underside had quite a bit of grime and minor corrosion along the pins of the IC underneath. More cleaning with IA and a peek with the scope showed a few tin whiskers forming. A bit of gentle work with a dental pick and more IA and swabs and was was pleased the were no more possible whiskers to cause a short circuit on the traces. However there was a bit of circuit board eroded away on the back side from the grime and batteries leaking at the (+) battery tab trace. I gentle cleaning of the board to expose some fresh copper and a repair trace eye soldered into place with silver bearing SMD paste and I was satisfied with the back.

Now back to the front (button) side for some detail work. Both switches were a bit sticky with the unlock being the worst. More IA, swabs and dust off while gently working those switches had them clicking nicely in short order. Time to reassemble and see if success was my fortune.

A tiny bit of SMD rework paste on the back side was placed on the battery tab holes on the circuit board and then the board was placed in the back. Next a bit of paste was put on the battery negative ring pin and gently installed in the case making sure the pin extended through the circuit board. While using a board component clamp to hold the ring, case and circuit board firmly together I soldered the ring pin in place making sure enough time was used to allow the solder to flow thru the hole to the back side. I should mention at this point that while inspecting the board traces I had noted which places on the top would make good test points to assure I had a good solder connection on the back side since it is impossible to see once soldered in place. Once I was confident the negative ring pin was soldered appropriately I moved on to the battery positive tab installation.

The battery (+) tab pin is a bit tricky to install. It slides in a slot in the case and if the pin is off ever so slightly can be quite challenging to hit the circuit board thru hole. Once in place a quick bit of soldering and checking the test points confirmed all was soldered in place. A bit of IA and a few swabs cleaned off the residue where I had soldered and a quick look with the microscope camera for any stray bits and I was ready for batteries.

With the batteries now in place I first worked the lock switch. As was hoped, the red indicator light worked. Next I tried the unlock switch, well there was no green light. At this point I placed the fob under my digital scope and pressed the unlock switch again. As hoped, the camera did see the green LED light up faintly. At this point I went to the car and decided to give it a go.

SUCCESS!!! The fob worked both the lock and unlock functions. At this point I decided to go ahead and finish snapping the front of the case into place. Order some new FOB button pads (the old ones are in poor shape) and after a bit of research ordered a new green SMD LED to replace the bad one.

Total time spent repairing, about 2 hours with cleaning. Cost, less than $1 in supplies for cleaning, $5 for new batteries. So far it looks like about $10 for new remote buttons and less than $2 for a single LED. I am quite pleased with the outcome.

 

I need to separate my corroded board from the FOB case but not having much luck as I don't want to force something and break it. Do you have any pics or links from your research?

 

The corroded board can be cleaned with baking soda and a dry toothbrush

You might try a cell phone repair shop if circuit lines not intack as they have the skillset / liquid solder

Battery contacts with a pencil eraser

rubber buttons and the microswitches under the buttons avail on E - bay for the specific X300 version

Now to read the posting

 

VicTrader, It has been 5 years since I did that repair and honestly I do not remember all the details. I used care, alcohol and a soft tipped brush to clean around the board to soften the grime build up aiding in removal.

 

Deoxit seems to do a better than most product that dissolves electrical corrosion.

 

I was surprised to even GET a response, as I saw it was 5 years ago, but glad for the info.
I added some pics of my fob, and the big question is how to remove the + tab and - tab. The + tab appears to be soldered to top of the board to the left of that coil. I am an electronics hobbyist and used to be a bench tech at a computer board repair company, so I can be slow and careful (I hate redoing work I rushed the 1st time) . Which solder joint di you think may be the (-) tab?

Does This plastic tab at the bottom hold in the circuit board in any way?

I am told to remove the + tab 1st, then the negative. Do these have to be desoldered on the top side of board 1st?

I think the + tab is soldered next to that coil and that has to be desoldered

 

The - is to the right of the "100", the + to the right of the neg. Make sure that you push the + all the way in when resoldering or the batt cover won't seat.

 

I appreciate the confirmation, and clarification, and now I get why the tab has to be de-soldered and removed to remove the board.
The tip about pushing the + so battery cover will seat is good advice too.
BTW do you think this can this be cleaned in a harbor freight ultrasonic cleaner without damage, or something like a spray CRC NF Precision Cleaner (Non Flammable)? CRC NF Precision Cleaner (Non Flammable) – Polyfab Technologies

 

I just used NAPA Electrical Cleaner, toothbrush, and a jewelers screwdriver to scrape the more stubborn deposits.
That’s 0.1mm cu wire wrapped around the black spool. Be very careful doing anything around it.

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