replacement laptop keyboard doesn't work but is still registered in device manag - Page 1
Forum section: electronics / beginners

author: dhkim
author_rank: Newbie
timestamp: July 22, 2012, 09:59:43 pm
content: It doesn't work at all, but is in device manager and even when trying to update driver or whatnot, it's supposedly fitted with the latest driver. The new keyboard is an exact copy of the old keyboard, and the old one works fine after switching back and forth to try to figure out what the heck is going on.any help would be greatly appreciated. Thanks.

author: Psi
author_rank: Super Contributor
timestamp: July 22, 2012, 11:53:12 pm
content: Laptop keyboards, afaik, are just dumb switch arrays. The driver is for the keyboard IC or chipset on the main board. Even when you change the keyboard you still use the same driver.Are you sure it's the correct keyboard model and that you put the flex ribbon cable in correctly with the little tabs pushed down?

author: dhkim
author_rank: Newbie
timestamp: July 23, 2012, 12:14:35 am
content: i was told as much about the drivers, but still thought i'd include that info just in case someone asks. I've definitely put the cables in correctly with the tabs down. I've switched back and forth with the old keyboard and the new one, and the old one ALWAYS works and the new one never works. I'm just a bit baffled that device manager recognizes it as being fine, but not a single button works. I'm reasonably certain the keyboard is compatible, my laptop model is a hp dv7t-4100 and it's listed as being compatible with this particular keyboard, and the same info. is listed even with different replacement part companies. I'm becoming more and more suspicious that this is the wrong keyboard, but it sure looks exactly the same too.Some more info (once again, not sure if pertinent): I/O Range: 0060-0060, I/O range: 0064-0064, IRQ 0x00000001 (01) and no conflicts.

author: Psi
author_rank: Super Contributor
timestamp: July 23, 2012, 01:35:47 am
content: Have a close look at the end of the ribbon cable on each.Check that there are the same number of pads and that the pad spacing is the same.

author: G7PSK
author_rank: Super Contributor
timestamp: July 23, 2012, 08:07:58 am
content: Also check that the end of the ribbon is clear of oil grease or varnish, rub the end with a clean cloth and a bit of alcohol or switch cleaner. Could be that there is a cabling fault with the new one.

author: amyk
author_rank: Super Contributor
timestamp: July 23, 2012, 09:24:00 am
content: The keyboard on this model is an 18 x 8 matrix.Here is the pinout of the keyboard connector showing the row and column positions.You can try finding the row/column coordinates of one key on the known good keyboard using a multimeter on ohms range, and see if the replacement also has the same mapping.(Why do you want to replace it anyway?)

author: SeanB
author_rank: Super Contributor
timestamp: July 23, 2012, 03:48:44 pm
content: I think the OP is under the mistaken idea that there is a driver device in the keyboard. The driver is in the laptop on the motherboard. If you disconnect the keyboard entirely and use a mouse to get the device manager the keyboard will still be there and shown as working, as the physical controller ( a soft core of an 8051 running in a portion of one of the south bridge devices) is part of the computer.The keyboard membrane is what is being changed, and it is entirely possible to have more than one layout of the switch matrix under the keytops while having the same physical layout and size and mountings on the unit. If the layout is wrong then you will have wrong keypresses, no operation of many keys, or no response at all.

author: Unknown
author_rank: Unknown
timestamp: March 09, 2015, 05:41:36 am
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