Re: what is the voltage tolerance for a iie?

[jonnosan <jonnosan@gmail.com>]

> > I've tried it with the keyboard plugged in, and with it not plugged
> > in, and it seems to make no difference. If I leave it turned on, after
> > about 30 seconds there are some blips that come out of the speaker,
> > and an LED (not the power LED, so might be the one you refer to)
> > flickers briefly, and the pattern on the screen changes (it's still
> > random blocks, just a slightly different arrangement).
>
> There is nothing wrong with either main board.
>
> That's the self-test running.  If it keeps running, it should also
> display "System OK" in the middle of the screen for a few seconds
> on each cycle.

How long is a cycle? I've watched the screen closely for a few
minutes, and also let it run by itself for a few hours and checked in
occasionaly, and not seen the "system OK" message.

> The simplest explanation for the behavior you are observing is that
> the keyboard ground wire (pin 13 of the connector) is broken, either
> at the IDC connector (from being pulled by the wire, for example) or
> somewhere along its length.  (This would also explain why Reset doesn't
> do anything.)
>
> If you have an ohmmeter, check for continuity between a ground trace
> on the main board and a ground trace on the keyboard, then shorten
> the path until you isolate the "open".
>

I tried this, and there seems to be a good connection between ground
on the main board and ground on the keyboard. Also the LED on the
keyboard lights up when power is applied - would that happen if the
ground wire in the connector was broken? a visual inspection didn't
show any obvious damage to either end of the IDC connector.

While checking the ground connections, I did notice that on the
keyboard, all the pins on the connector seem to be connected to each
other (i.e. if i put the ohmmeter on any 2 pins, I get a low
resistance reading). Is that normal?

Thanks for your advice

Regards

Jonno