Someone spilled water on an FC900R

In another corner of the internet, someone reported a water accident with a Leopold FC900R PD.

I offered to post the issue here, in the hopes of casting a broader net for help.

Here is the OP:

Hello, my mom accidentally spilled water in a few weeks ago, but I couldn’t act until now because I was busy and exhausted from work. I only turned off my computer and cleaned the water, I didn’t realize I should unplug it and place it downwards. It was fine the first few days, but then some keys aren’t responsive anymore.
I would like to know if my keyboard is hotswappable and how do I troubleshoot it? How do I know if I only need replace the switches or the PCB is damaged? Thanks.

The keys without key caps are non functional keys.

They were informed that the FC900 is not hotswappable. So they asked:

Then how would I know if the PCB is damaged or not? It seems really hard to check the state of the keyboard, because the design of this keyboard. From what I searched around the forum, it’s quite hard even try to open the case if you are inexperienced.

The other keys are still functioning.

Someone advised:

The PCB is presumably fine if that’s the case. You can try opening the switches as suggested, take care, and if that doesn’t work you can desolder the non-functioning switches and solder on working ones.

Does anyone have any additional advice for the problem?


I repaired a WASD Code not too long ago with the same problem.
I had to desolder all the switches to have access to the PCB, and found that some traces were broken because water came in a few vias and corroded the copper.
I had to reroute the traces with wires to make it work again.

The switches were all fine, but it may me different in your case.
If you want to be sure then a multimeter and an access to the bottom of the PCB will tell you.
If the switches are really not working, then it is a matter of desoldering the dead ones and solder new ones.
If the switches are making contact then it may be a PCB problem…


First thing to do is get a multimeter, switch it to beep-on-short testing mode, have someone ready to press a bad key, touch the two probes of the meter to the solder points of the bad switch in-situ, and have your assistant press and hold the key. It should beep if the keyswitch is working (and I expect this to be the case because water doesn’t usually get into the keyswitch enough to affect the crossbar, it usually soaks the base under the plastic bottom half).

Do this test for each keyswitch. This test saves you the trouble of desoldering perfectly good switches. If you find that any switches are bad, of course, you’ll replace them. If they all work, then it would be a matter of PCB vias being corroded and having to route around the broken vias using thin wires.


Thanks for your help, @Rico and @dchang0. I have sent the information on to the person who asked the question.

Now they are looking at replacement switches in case any of the switches went bad. They are thinking of soldering these onto the PCB:

It is to replace some MX Blue switches. They asked if these are the right kind.

I think they are, but they are rather pricey. Anyone know of cheaper alternatives? I’d say AliExpress, but quality and authenticity of Cherry parts may not be assured.

Also, they look to be plate-mount. Is that what would be wanted on a Filco, since it’s not PCB-mount?

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Beware, desoldering switches is not as easy as some may think and particularly with PCB using lead free solder.
You need a good iron and a good desoldering pump.
But if the person knows what it is doing why not (I personnaly did that several times) ?

If the PCB has 3 pins mount you can still cut the two prongs on the switches before soldering them, it is not at all complicated.

I think you can find cheaper switches and better/smoother with Gaterons Yellows, Gat X, etc.
Beware though that if the person intends to replace only the swiches that don’t work he should purchase the same model already installed (it look to be Cherry Blue, the cliky ones).

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Rico is right–desoldering is tough unless you use the right tools.

I have a Hakko 808 desoldering gun that makes it easy. I recently repaired a badly-soldered Preonic rev1 where the former owner didn’t use soldering flux. All the solder had to be sucked out, flux applied, then re-soldered. Without the 808 it would have been a nightmare job, which is why he dumped the Preonic for cheap. (You don’t have to have a power-desoldering gun, just a good manual solder sucker.)

If you run into lead-free solder, you can defeat it using Chip Quik (meant for desoldering surface-mount chips with lots of legs) or by adding leaded solder, then sucking away all the solder.

Re: Cherry switches.

Fakes are common. The real ones always have the CHERRY logo molded in the top. Keychron probably sells the real deal. You can tell when you receive them whether they are fake; the fake ones are pretty obviously cheaper-made than the real ones. Look for the famous gold cross-bar in the real ones.

We may make it sound scary, but really, with the right tools, it’s easy.