[Still UNSOLVED] T30 Keyboard Power Switch Doesn't Power On

[singbad]

Hi all,
I got two T30 keyboards that don't power up. But power down/suspend by the same power button works OK. As far as I can see the power button is a regular 2-lead key switch. Don't know what makes the difference.

Any ideas?

Best regards,
singbad

[madrigal]

Yeah, this is a well known problem with IBM T30 keyboards.
I think the problem is connected with different currents drawn via Power button when you turn on the laptop and when you turn it off. Unfortunately I have no working solution for its repair - after several attempts to replace rubber caps, to clean the contact areas etc. with no success now I have 2 or 3 keyboards for spare parts (keys).

[singbad]

I studied the "nonexistent document" and spotted the two pins that connect to the START button. In a working keyboard I measured about 85 ohms on button down.



I have opened the flex cable contact plates at the rear side of the keyboards.

One appeared to have been invited for a cup of coffee.

You can see severe corrosion at one of the aluminium leads and some kind of dust on the carbon pads.


I cleaned the contacts with cotton swabs and alcohol and restored the corroded line with conductive silver paint.



To improve the conductivity I slightly bent the metal parts* that hold the flex cable in order to increase the pressure on the contacts. I measured 160 ohms while holding the start button pressed. I think this should work, however, currently I don't own a working T30 for testing.

The other keyboard showed no corrosion, only dirt on the carbon pads. I cleaned them with alcohol and re-assembled with increased pressure: 85 ohms.

*) the two strips of steel sheet that press the gold pads of the flex cable tightly against the carbon pads of the keyboard. Conductive carbon "paint" isn't the contact material of choice but is widely used in the keypad industry.

Best regards,
singbad

[singbad]

I got a working T30 to test the 'repaired' keyboards. They don't start up the machine. The other one that I remembered working doesn't start either. 85 ohms is apparently too much resistance. A good working keyboard shows a start-button resistance of less than 15 ohms.

Sorry, I have no solution yet. Maybe I'll have to completely destroy a keyboard to discover the matrix and measure line resistances. I got an incomplete keyboard which I used for spare keys.

Look forward for photographs

Best regards,
singbad

[singbad]

I cracked 60 tiny auminium rivets and disassembled the keyboard so far.


There's a silk-screen printed multi-layer circuit film underneath that resists further analysis. The design looks like a macro-scale integrated circuit.



I tried to remove the protective cover layer with acetone but it's very hard. It wouldn't make no sense anyway. There's nothing to solder at a wooden box (German proverb).

All I can say is that the resistance of the printed leads has increased to 30 ohms (GND) and 15 ohms (-PWRSWITCH).

Best regards,
singbad

[EDITED]

[BruceDickinson]

singbad--

I was researching an issue with my T30's power button and came across your posts. Though you don't appear to have solved your problem, I just wanted to say thanks for your efforts and posting those nicely-labeled pictures. Good luck.