How to troubleshoot broken Novatouch?

RichardinFinland

20 Jul 2016, 16:53

Unplug working Novatouch, plug in broken one, makes connect sound, never sends keystrokes.
Have opened board and verified that all springs are where they belong under domes.
Have tried more than one computer.

Will try rebooting with broken board alone plugged in.

I have other novatouches I can swap parts with, and a voltmeter.

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Phenix
-p

20 Jul 2016, 18:25

Maybe swap the pcb? Would be my first guess(bad controller) but better wait for someones answer with more experiences ;)

RichardinFinland

20 Jul 2016, 18:25

Problem discovered. The component in C15 is broken off. What was part C15?
http://i.imgur.com/ZoyvhD8.jpg

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Laser
emacs -nw

20 Jul 2016, 20:18

Where did you get that report? I have a strong feeling, since the keyboard is *capacitive*, you just have to look at the circle nr. 15, if there is one.

RichardinFinland

20 Jul 2016, 20:22

What report? I got a magnifying glass and compared the working pcb to the broken pcb, and noticed the missing C15 component. Which I believe is a capacitor. I just need to know its value to buy a replacement :( I could unsolder a neighbor of it's, but I'm assuming they have the same value, and I don't know that's a safe assumption.

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Laser
emacs -nw

20 Jul 2016, 20:25

Ah; your question wasn't that clear ;) GL

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chzel

20 Jul 2016, 20:27

Laser, Richard means this:
Spoiler:
ZoyvhD8.jpg
ZoyvhD8.jpg (346.22 KiB) Viewed 820 times
Which is a capacitor, unfortunately of unknown value.
Maybe a closeup pic can help. I'd bet my money on 100nF, but it's a gamble.

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Wodan
ISO Advocate

20 Jul 2016, 20:28

Is there any printing on the capacitor (C15) ?

Don't think the EXACT value matters ...

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dorkvader

20 Jul 2016, 20:31

Yeah its a cap. The chip is a Topre-specific TP1684 capsense controller.
http://www.kbdmania.net/xe/best_article/8164664
According to that, pin 2 (the one that goes to C15 and test point) might be some sort of bias control, which would explain why it's not working without it. It goes to ground, so it might actually work if you solder bridge it.

Now as to what value it actually is... I dunno. It's possible any capacitor in that package size would work (I first though it was a bypass cap, in which case, pretty much any value is fine, but it would still probably work without it) but if it's some sort of bias capacitor then you'd want one to be a similar value.

Do you have basic LCR meter functionality on your volt meter? I would measure the C15 on the working board and report back. I'm in Italy right now, and would be glad to help once I'm back in the USA, if you want to wait a week.

RichardinFinland

20 Jul 2016, 20:53

I have a multimeter, I don't think it measures capacitance all to well though, and I'd have to de-solder a neighbor right to measure it right?

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