Izaq

Quickfire Rapid-I 200Hz PWM flickering :-/

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Izaq    0

Well... the dealer can offer me a new Rapid-I as a replacement. I'm not really interested in that. So let me change my question to:

 

1:  Are all CM backlit keyboards driven by a 200 Hz PWM, or can I ask the dealer for a different CM keyboard without programmable LEDs? (some that are shining all the time)

 

2:  I might try to repair the keyboard in stead (since I probably will have to do this several times). What is the typical defect? Burned out LED or a controller fault? I might be able to replace the LEDs but not the controller.

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world    84

1: My CM Storm Quickfire TK doesn't seem to flicker, so I think CM's other keyboards might not use PWM

 

2: Most likely, it's a burned out LED

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Izaq    0

@world

 

Thank for the reply. Yet...

 

1: Have you seen the flicker on the Rapid-I? If not then I am not sure how you could tell the difference. Some people seem not to be able to see it. So the answer doesn't help me at all. Perhaps the TK uses a PWM aswell, but you are not able to notice it.

 

2: I can replace the LED. But just as I type this I notice that a SECOND key has stopped shining. I'm not going to spend hours on soldering duty to keep this horrible device running and I am not going to send this for repairs/replacement every other week.

 

Do you want me to take the device appart, offload the software through JTAG, decompile it and figure out why a 200Hz PWM is being used? It is perhaps faster than waiting for support figuring out how to ask the engineers how they have constructed it.

 

But then again: Engineers who do not have the wits to protect the LEDs from ESD most likely have no idea why using a PWM driver on a high contrast display device is a poor choice.

 

I give up. This is a waste of time really...

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world    84

Izaq, I have seen the flicker on my Rapid-I. I don't use a backlight most of the time so it hasn't impacted me much, but I definitely can see the flicker.

 

I understand what you're saying about PWM usage on this type of device, and I completely agree with you. 
 

You can JTAG the board if you want, but I would recommend against it, since first of all you'll be voiding your warranty, but second of all you probably won't find specifically why PWM is used. 

 

If I had to guess, I would say that PWM is used to save power on the keyboard. I don't have a USB ammeter, but you'll probably see a decent bit of power draw on the Rapid-I when the backlight is on max, and the designers wanted to keep the power envelope under a certain wattage while using their choice of LED. Of course, this could have been mitigated by using a different type of LED, but unfortunately, that's what the designers chose.

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Izaq    0

@world

 

Interesting. Perhaps a TK is the better solution for me then.

 

My point is that it will get too expensive to mail the keyboard back and forth to the dealer to get it repaired. If 2 LEDs can burn out within the first month chances are that many more will die in the life time of the keyboard. Therefore I need to be able to repair it myself.

 

You are most likely correct that PWM saves power since LEDs appear brighter at 100% power for 10% of the time, than 10% power 100% of the time due to how the eye is sensitive to light.

 

Still it would be wiser to use a 1KHz PWM rather than a 200Hz which can be seen by the eye.

 

Thank you for your response!

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Izaq    0

Oh and a final onte (if this information is ever sent to the engineers):

 

The LEDs are not shining in the same color! :-/

 

As you can perhaps see in the second picture I posted, the 6-button shines with a yellowish tint, the letter Y is clear white and H and N are inbetween white and yellowish. It might not look too bad in the picture since it is kind of overexposed. Yet in real life many of the buttons appear quite dirty.

It is not the key caps but the LEDs themselves.

 

- F-buttons are white.

- top row (numbers) are all yellowish.

- TAB+Q is yellow, then from W to O is bright white

- A to L row is yellowish... and so forth.

 

It seems the LEDs have been picked from different tapes with different batch numbers.

 

If possible please let the design dudes know that, when using cheap LEDs with low color consistency grading you have to make sure that every device is built from a single batch of LEDs only to avoid (or reduce the risk of) color inconsistencies.

 

I thought this was sort of basic stuff.

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world    84

I'll be sure to forward this to them. Thanks a bunch for your insight, and sorry that the keyboard isn't really working out for you :(

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