Strange keyboard malfunction

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JamesP
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Joined: Thu Jun 17, 2004 2:44 pm

Strange keyboard malfunction

Postby JamesP » Thu Jul 08, 2004 8:07 pm

Hi,

I'm trying to get my keyboard working. The "(" and "/" keys on the numberic keypad do not work.

I have been following simbo's informative instructions for repairing keyboards, I have dismantled the keyboard, cleaned it and the klicks too. All this looks ok. No black dots of pcb disease to be seen either.

I tried the klicks on the keyboard before re-assembly - it worked perfectly. Screwed whole thing back together - the same two keys don't work again!! :(

So I unscrew it again, does not work. I've resoldered the connections in this area of the board and tested the tracks with a multimeter - they appear to be ok.

I was just about to give up when the keys worked again. Moved the keyboard slightly - does not work now ... aaagghhh!!! :x

I'm stumped. Any ideas?

All i want to do is use the keyboard rewind and loop in Cubase!

Thanks!

James.

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jens
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Re: Strange keyboard malfunction

Postby jens » Fri Jul 09, 2004 12:17 pm

JamesP wrote:The "(" and "/" keys on the numberic keypad do not work. [...] All i want to do is use the keyboard rewind and loop in Cubase!

I actually thought of using those Cubase-functions in the moment I read about those two keys. :D
And I see their importance to you.
Unfortunately I don't think I can help you. Sorry... :?
Greetings, Jens

Falcon030 - TT030 - Mega/STe - 1040 STf - 520 ST+ - ST-Book - Milan 060

simbo

Postby simbo » Fri Jul 09, 2004 12:21 pm

hi man dont panic

ok i think i know what the matter is

on the keyboard is a controller chip

check all of its pins are soldered properly and make sure its seated correctly although this is NOT the likely cause

if this is aok it sound like a hair line crack in the keyboard pcb
this again is a normal thing
maybe you can even remember droping something on it
like an aftershave bottle or other like the mouse or a mains plug etc


so look for

1} dry joints on the controller ic pins
2} a hairline crack in the board
{usualy around the underside of the mouse ports}

as its a problem with the keys directly above the mouse this is more likely

a tip is to track back the tracks from the dodge keys and youll find this near the edges of the board or one of its other parts that gets strained



if you get no luck take a picture of both sides of the board and send me a copy by pm

ill see where the problem is and let you know

my camera is realy crap so going by this
i use a scanner and place boards in
this takes a very clean picture you can shrink or resample to fit in a few hundred k

ye .. sounds like a crack or some other print error
esp as its an intermittant fault



let me know




ps these things are sent to try your patience so keep smiling and grin and bear it till we get a look at a scan or a photo or you find the flaw

:roll:

if this fails dont worry i can send you a working keyboard for a shiping cost in return you send me yours ill repair it and it can do for the next guy

i also have about 20 spare psu that all work as new...
{reconditioned and upgraded a little}

however i think your nearly there

so... keep plodding on and dont take no for an answer ....



a few tips about keys

we know two things the "(" and "/" on the numeric keypad dont work
so
all keys in these boards are a matrix that uses a system called mux multiplex "strobed" to read off the keys

so the whole keyboard has rows of common connections and also columbs of common connections

ie each key is independant of a common rail to the next row down up etc... but shares a row common

so if these two keys fall into the same row common
as i see they do and are in the same row so will share a common
row connection


i think what ever is the flaw it is common to both keys

so look for a join in the tracks between these two keys
then follow both back

again carefully study for any cracks or lifted broken tracking


let use know if this works



tips for cracks in the board

1} dress the crack or lifted pcb print either side {take the green paint carefully of the pcb print each side of the crack

2} carefully with a 12watt iron and some flux spray or fine resin cored solder tin all the tracks till there shinny lead tin coated
just 5mm each side of the crack

3} get a pices of wire has to be the multi conductor stuff
{has about 20 - 30 thin strands}

4} tin a single strand of this
5} now you can carefully solder little links to make over the tracks i use a magnifier sometimes and a strong light
6} the single most important thing is to drill two small .5 mm holes one each side of the crack
this way youll stop it spreading again

7} is to carefully test each track for continuity using the diode range on meters


BE CAREFULL never use the beeper low resistance continuity check on computers only the diode test range
so youll need to look for a 0.00 reading or so,,,, instead of a beep

as the voltage/current this range uses on most meters will damage chips

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JamesP
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Postby JamesP » Fri Jul 09, 2004 1:13 pm

Yeh, I think the keyboard chip is in OK, I pushed it in and resoldered the pins to be sure.

I'll take a look at the pcb again. Don't recall dropping it (can't say no one else in my house didn't tho' - every time I come home there's something new to fix for the people who think brute force is the only way to make door/plug/lid/otherthing fit in hole :lol: )

These keys definately share a common connection. That was what I was looking at. I tried to 'bridge' the connection between the points on the board that pressing the key should link, by touching with a piece of wire - this never worked though.

I'll look again with strong light tonight (sounds like a bad song..). If no joy I'll whack it on the scanner.

Thanks simbo for your kind offers of help, it's people like you who make the world a better place!

I'll let you know how it goes...

James


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