FC660m Easy arrow cluster LED mod

[rety20]

FC660m arrow cluster LED mod

Found some unused LED holes while analyzing the PCB of my FC660m.
Tryed things out and we seem to have a new thing going on here! An easy, working LED mod!

Materials & Tools

>4x 1.5mm LEDs in the colour of your choice
>1x 1kΩ resistor  (Brown, Black, Red) or 1kΩ micro resistor (102 written on it) *MIGHT NOT BE NEEDED*

>Solder
>Soldering Iron
>Small Philips head screwdriver
>Side Cutters

Resistor

*RESISTOR MAY NOT BE REQUIRED*
Since the LEDs are in series, they seem to produce brighter colours without the resistor, just solder a small piece of wire there instead, BUT this may burn out the LEDs or blow up the circuit board or something. It worked fine for me but what do I know? It's hard to trace the PCB without looking at the front. Do so at your own risk.

Alright, above the arrow cluster on the vack of the PCB is to tiny contacts labeled "R4" those are the contacts you need to solder the resistor to. Simply bend the resistor so that the leads touch the contacts and solder them into place. Trim off any part of the resistors leads that are sitting past the pads with sidecutters.

It doesn't matter which lead touches which contact because resistors aren't polarized, make sure that the two pads aren't soldered together, otherwise your resistor will shortout of the circuit.

LEDs

Now thread the LEDs through the top of each switch and through the holes in the PCB, LEDs are polarized so make sure that the longer lead (the anode) is sticking through the holes labeled with a "+". Next bend the leads of the LEDs from the back like in the picture below so that they stay in place while you solder them.

Solder

Solder each of the LED leads into place, remember not to let the joints touch!

Trim

Snip those bad boys off with the side cuttters

Finished PCB


There we go!

We have lift off! I'll definately have to get some blue LEDs to match the rest on the board.

Caps on

More

White WASD caps and normal indoor lighting

White WASD caps and normal dark lighting

Stock PBT caps and normal indoor lighting

Stock PBT caps and normal dark lighting

[bueller]

Awesome work man!

[rety20]

Awesome work man!

Thank you!

[rowdy]

Amazing!

Why has no-one noticed this before?

I wonder what LEDs there were supposed to do originally?

Maybe some sort of "arrow lock", akin to numlock?

[rety20]

Amazing!

Why has no-one noticed this before?

I wonder what LEDs there were supposed to do originally?

Maybe some sort of "arrow lock", akin to numlock?

Apparently some Razer Blackwidows have spots for arrow LEDs aswell, I was astonished thought that nobody had ever bothered reading the labeled holes on the back of the PCB I haven't desoldered the switches to trace the connection on the front of the PCB but it seems that the LEDs are wired in series to the controller "area" directly. If they had a plan when the PCBs were being manufactured but then scrapped the idea before implementing the firmware then that must have mean that someone just threw power to the LEDs just for us. It's like a secret preasent from whatever Leopold employee wrote the firmware

[dorkvader]

Amazing!

Why has no-one noticed this before?

I wonder what LEDs there were supposed to do originally?

Maybe some sort of "arrow lock", akin to numlock?

Apparently some Razer Blackwidows have spots for arrow LEDs aswell, I was astonished thought that nobody had ever bothered reading the labeled holes on the back of the PCB I haven't desoldered the switches to trace the connection on the front of the PCB but it seems that the LEDs are wired in series to the controller "area" directly. If they had a plan when the PCBs were being manufactured but then scrapped the idea before implementing the firmware then that must have mean that someone just threw power to the LEDs just for us. It's like a secret preasent from whatever Leopold employee wrote the firmware

Excellent mod! You are a true GeekHacker!

I am actually very interested in the electrical design of that LED cluster. You see, unless they designed for very low Vf LEDs, they can't all four be in series. Please let me know if you have a multimeter and are willing to test a little. You wouldn't have to desolder.

The middle two are in parallel with eachother, and I see a line from the right one (left arrow) that likely goes to the microcontroller. It's entirely possible that they are all in parallel off that resistor, but if that's the case, then it'd likely be much higher value.

Maybe there are two parallel strings of two LEDs in series. That's how TG3 did it on the TG3 BL82 (though TGE has one resister per pair of LEDs) and would account for things.

[rety20]

Multimeter is at the ready!

[rety20]

Excellent mod! You are a true GeekHacker!

I am actually very interested in the electrical design of that LED cluster. You see, unless they designed for very low Vf LEDs, they can't all four be in series. Please let me know if you have a multimeter and are willing to test a little. You wouldn't have to desolder.

The middle two are in parallel with eachother, and I see a line from the right one (left arrow) that likely goes to the microcontroller. It's entirely possible that they are all in parallel off that resistor, but if that's the case, then it'd likely be much higher value.

Maybe there are two parallel strings of two LEDs in series. That's how TG3 did it on the TG3 BL82 (though TGE has one resister per pair of LEDs) and would account for things.

Multimeter is at the ready!

[xandr]

Great mod!

What I find even more interesting though is the fact that the PCB appears to have mounting holes for the JP layout keys that are similar to ISO like the big enter key and the \| next to the doublequotes. I doubt the plate does have matching holes though, or does it? An ISO FC660m would be something I'd like quite a lot.

[Grendel]

From the looks of the PCB at least the up and down LED's are parallel. Makes more sense too, having all in series would limit the forward voltage to 1.25V (5V/4 -- actually less since you still need a voltage drop on the resistor for limiting the current.) Since LED's have a wide range of FV (most are between 1.6V and 3.6V) wiring them in parallel makes it more flexible (although ideally every LED would have its own resistor.) BTW, the resistor is 1kΩ, the 2 designates the number of zeros in this position: brown = 1, black = 0, red = 2 zero's --> 1000. A reasonable value w/ the LED's usually used for backlighting keys. IMO the resistor is required to limit the current, if you install a 0Ω jumper the LED's will possibly draw 20mA+ each w/ 5V across them -- will shorten their lifetime considerably and may exceed the allowed current draw on the USB port.

[rety20]

Great mod!

What I find even more interesting though is the fact that the PCB appears to have mounting holes for the JP layout keys that are similar to ISO like the big enter key and the \| next to the doublequotes. I doubt the plate does have matching holes though, or does it? An ISO FC660m would be something I'd like quite a lot.

Would be cool, unfortunately at least in my model the plate is ANSI only.

[rety20]

From the looks of the PCB at least the up and down LED's are parallel. Makes more sense too, having all in series would limit the forward voltage to 1.25V (5V/4 -- actually less since you still need a voltage drop on the resistor for limiting the current.) Since LED's have a wide range of FV (most are between 1.6V and 3.6V) wiring them in parallel makes it more flexible (although ideally every LED would have its own resistor.) BTW, the resistor is 1kΩ, the 2 designates the number of zeros in this position: brown = 1, black = 0, red = 2 zero's --> 1000. A reasonable value w/ the LED's usually used for backlighting keys. IMO the resistor is required to limit the current, if you install a 0Ω jumper the LED's will possibly draw 20mA+ each w/ 5V across them -- will shorten their lifetime considerably and may exceed the allowed current draw on the USB port.

Whoops! Thank you, I fixed the guide. I plan to replace the LEDs soon anyways so they can be the guinea pigs for life expectancy but I've had my keyboard on for close to 18h and haven't had any problems powering the keyboard, what should I look out for though if it is? Just a message in my OS saying that there is a problem with the port?

[Grendel]

Whoops! Thank you, I fixed the guide. I plan to replace the LEDs soon anyways so they can be the guinea pigs for life expectancy but I've had my keyboard on for close to 18h and haven't had any problems powering the keyboard, what should I look out for though if it is? Just a message in my OS saying that there is a problem with the port?

Worst that can happen is that the OS shuts the port down for drawing more than the requested current. Unless you create a short, then all bets are off. :/ I would suggest to try reverse engineering the schematic for that section, should be pretty obvious what the resistor has to be. I do have one of these boards somewhere, I'll take a look later tonight.

[Grendel]

Yep, the LED's are connected in parallel. All their anodes are tied together and connect to the resistor (that connects to +5V on the other side), all their cathodes are tied together as well and connect directly to the Holtech controller. I don't know what the controller can handle on that pin, but I'm sure 80mA would be too much in the long run so stick w/ a resistor ! I just threw in four white LED's (from Maxkeyboard) and a 1k resistor, plenty bright

Edit: just after closing it up and stowing it away I realized that I didn't check if the pin on the controller is connected to ground (meaning that the controller wouldn't drive the LED's). If someone could check that ? Just measure the resistance betw. any LED- pad and GND, if it's less than an ohm the controller has nothing to do w/ the LED's.

[rowdy]

Looks like someone else did notice!

[dorkvader]

Looks like someone else did notice!

That one must use a different PCB: you can see on the pictures of this FC600M that there are many keys which cannot be backlit (no holes for LED)