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New to anything electrical, and I'm trying to make an urgent fix for my wife's keyboard. She has a disability, so needs a specific keyboard to work, and the USB plug on the keyboard has been damaged and the male USB terminal is unlocatable. We're in lockdown (NZ) and it's likely to be a week or more before a replacement arrives.

I've done as much searching as I can, and I feel like splicing another USB cable onto the end of this one should be entirely doable.

BUT. The keyboard cable has 5 internal wires, and none of them are red. It has blue, green, black, white, and yellow. I've run on the assumption that yellow might be a faded red or orange, but wiring that and matching the others (replacement cable wiring is red white black and green, so leaving blue disconnected currently) hasn't produced anything. The keyboard manufacturer is Penclic - I've been unable to find anything useful about their wiring from my searches, but I don't know if there is a specific resource that might provide some help.

My question(s) is (are), which of these colours is most likely to be the +5v, or is it somehow unusual? And, is it possible to repair a 5 wire keyboard, by splicing with a 4 wire USB cable? Additionally, if I just keep trying combinations, am I likely to destroy something? Have I already??

TIA and apologies for anything important I forgot, or totally unnecessary detail I did include.image showing keyboard wiringenter image description here

Additional images: enter image description hereNenter image description here

Glueless: enter image description here

Macro: enter image description here

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Is that a "V" I spy?

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  • \$\begingroup\$ Checking the other ends of the wires inside the keyboard would probably be a good next step. \$\endgroup\$
    – Hearth
    Commented Oct 27, 2021 at 1:08
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    \$\begingroup\$ D+ D- S G and V are clearly marked. Am I the only one seeing that??? S= shield G=Gnd, V= V+ Colors are irrelevant, you're gonna replace the whole cord, right? \$\endgroup\$
    – Kyle B
    Commented Oct 27, 2021 at 2:53
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    \$\begingroup\$ @kyleb haha took me a couple of go's to get good angles of the letters, don't judge anyone but me 😅 yeah I will, have just tested with a quick twist and it's working! Thanks \$\endgroup\$
    – craigg123
    Commented Oct 27, 2021 at 3:05
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    \$\begingroup\$ @craigg123 Excellent brother. Very happy it worked out for you! Wishing the best for you and your wife. \$\endgroup\$
    – Kyle B
    Commented Oct 27, 2021 at 5:44
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    \$\begingroup\$ Thank you @kyleb - it might seem minor, but for someone with her challenges and, with everything else going on, it was a big win today. Take care in this crazy world! \$\endgroup\$
    – craigg123
    Commented Oct 27, 2021 at 6:16

1 Answer 1

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Usb wire colors are a guideline but not mandatory. You should never actually assume a wires color will mean it's actually a specific function in any case. Always measure it.

The USB data lines will typically be two thin parallel tracks on a pcb. Finding which is which may be difficult without tracing them to an IC and having a datasheet to find out which pin should be which data line.

Power and ground are easier, as the ground plane tends to be bigger and the power lines bigger than data but smaller than ground. A capacitor with labeling would be best.

But as you see in your last pictures, there is markings on the board.

Ground seems to be blue.

Shield is black but it is just tied to ground with a 0 ohm resistor but they decided to solder unto a usb A connects shield instead. You can probably ignore that wire, which answers your 5 wire vs 4 wire question. If your replacement cable has a metal foil then that's what you should connect to the shield.

V+ may be white, with data - and data + the yellow and green but the wires are blocking the white letters that likely show D+ and D- and V+ or VCC.

Based on the last picture the board has a common gl850g usb 2.0 hub IC. The datasheet shows its pin outs and you can use your multimeter in continuity mode to confirm everything, it's a simple IC. https://www.kean.com.au/oshw/WR703N/GL850G%20USB%20Hub%201.07.pdf

Frankly you should just ignore the original cables and colors. Desolder the wires, clean the board and trace the pins to the IC, and add your own cable as required. pins 23 5V in, 15 ground, 25, 26 usb upstream data pins, are all you need to figure out what's what.

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    \$\begingroup\$ Awesome, thank you @Passerby! I did a quick test by twisting the wires and it's working. I'll clean the solder off and do a proper job before it gets used. Really appreciate your help! \$\endgroup\$
    – craigg123
    Commented Oct 27, 2021 at 3:09

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