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Repair Non-Working FOB DIY

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velorider
Posts: 207
Joined: 17 Feb 2009, 13:16
Year and Model: 2005 S60 T5
Location: Long Beach, CA
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Post by velorider »

I'm sure I'm not the first to do this but I couldn't find anything while searching. One of my FOB stopped working a few years ago and getting a replacement was too cost prohibitive. I previously tried repairing it but was unsuccessful. This should work for both the earlier FOB without key and new knife key style FOB.

While at Pick-A-Part pulling a trunk latch there was key FOB in the key hole. About a month later I started wondering if I could just transfer the microcontroller (IC) from my non-working FOB onto the junkyard FOB. I figured the coding would be in the IC, so by transferring my IC to the junkyard FOB it would allow the junkyard FOB to work with my S60. So today I tried and it worked! It took me about 30 minutes to desolder the IC from both boards and solder mine IC onto the junkyard doner board.


The IC is the 8 pin black square thing on the board. What's important to notice is the orientation of the IC. Look for the dimple on the top of the IC.

FOB2.jpg
FOB2.jpg (144.76 KiB) Viewed 448 times
FOB1.1.jpg
FOB1.1.jpg (136.81 KiB) Viewed 448 times

This isn't a step by step DIY since those that are attempting this already know how to solder.

1. Use a fine conical tip.
2. Add new solder first to the IC to make desolding easier. It's ok to add way to much and bridge pins.
3. There is a capacitor just above pin 7 and 8, that easy to desoldering when removing the IC.
4. I have a cheap knock-off chinese desoldering hot air station, I set the temp at 380 and the air very low, 2 or 3.
5. After removing the IC from the doner board, clean the pads with desolder braid.
6. Lightly tin the clean pads, this will be enough to solder the IC onto the doner board.
7. Position the IC from your non-working board on the doner board and using the desoldering station flow the solder.

This was my original board after desoldering the IC, notice the cap above pin 7 and 8 is missing. Also notice the globs of new solder to help flow the old solder to make removal easier.
IMG_20220101_153504158_HDR.jpg
Here is the IC from the doner board.
IMG_20220101_153530917_HDR.jpg
Attachments
434MHz_SAW-based_oscillators_and_transmitters.pdf
(180.27 KiB) Downloaded 200 times
BFR92A_Rev4.pdf
(277.27 KiB) Downloaded 105 times

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