Thanks tech!
I'm not really sure about the SWIM chip, though, so I'm asking you a couple more questions: when you're talking about crowbar activation, what do you mean exactly?
What we're seeing here is this: when we turn on the portable and the video cable is disconnected, we almost always hear a good starting chime (a couple of times we obtained a death chime at a certain point for unknown reason). Current measurement seems "normal" at this point. There seems to be some noise coming from the floppy as if it was looking for a track, you know, the normal noise you hear from a good floppy drive every time you turn on a classic mac with no disk inserted and that happens even before the chime.
After the chime is completed, current level drops to 0A and the system shuts down.
When the display cable is connected instead, we hear a different kind of noise, which sounds more electrical (could this be the crowbar activation?), and we never hear the chime. Also with the display connected we observed a couple of times the CC light on the test power supply that we're using - that power supply is tolerant up to 3A, so there must be a short somewhere here.
Given this, how much is it likely that the SWIM chip is involved? I'm very very ignorant about this, but it would seem to me that if such chip is dead, we should never hear a good chime coming from the machine. I'm referring to your topic here about the issue, but it seems a different behavior. However you're the master about portable issues, so I'm totally dependent on your judgement on this!
We're going to see if there are broken traces or cap goo in the area nearby the reset buttons you mentioned.
I'm not really sure about the SWIM chip, though, so I'm asking you a couple more questions: when you're talking about crowbar activation, what do you mean exactly?
What we're seeing here is this: when we turn on the portable and the video cable is disconnected, we almost always hear a good starting chime (a couple of times we obtained a death chime at a certain point for unknown reason). Current measurement seems "normal" at this point. There seems to be some noise coming from the floppy as if it was looking for a track, you know, the normal noise you hear from a good floppy drive every time you turn on a classic mac with no disk inserted and that happens even before the chime.
After the chime is completed, current level drops to 0A and the system shuts down.
When the display cable is connected instead, we hear a different kind of noise, which sounds more electrical (could this be the crowbar activation?), and we never hear the chime. Also with the display connected we observed a couple of times the CC light on the test power supply that we're using - that power supply is tolerant up to 3A, so there must be a short somewhere here.
Given this, how much is it likely that the SWIM chip is involved? I'm very very ignorant about this, but it would seem to me that if such chip is dead, we should never hear a good chime coming from the machine. I'm referring to your topic here about the issue, but it seems a different behavior. However you're the master about portable issues, so I'm totally dependent on your judgement on this!
We're going to see if there are broken traces or cap goo in the area nearby the reset buttons you mentioned.