Re: [NTLK] MP2x00 hot in the back: anyone got that problem?

From: Johannes Wolf (jwolf_at_xe.estec.esa.nl)
Date: Fri Feb 15 2002 - 03:08:21 EST


Hi Paul,

indeed, your problem seems weird.
Ok, but let us go back to a logic step by step analysis.
If you leave the Newt unpowered for a couple of minutes the heat source will
start to cool down.
I strongly assume that the source is a chip.
Chips have a low heat capacity and will therefor cool down faster than the
PCB which has a higher heat capacity.
So a good idea would be topower the Newt in open condition.
Dont worry, no problem as long as you place the Newt on a flat and isolating
pad, I did it a lot of times.

Possible sources:
If you look on the display (in normal operating position), the SER-001 board
will sit more on the left side towards the middle.
On the right side you have the IR port, a little chip from Cirus Logic and
the Newt interface chip for the NIC port.
But due to the fact that the Newt back has a thin metal surface (for
shielding purposes) the heat is distributed over an area and you would not
be able to locate a punctual source.
With the Newt opened you have a better chance.

What I can imagine is that the SER-001 interface chip had a so called
latchup.
During latchup the involved chips heat up a lot.
If you are lucky, the chip survived.
But you can check this easily by testing the functionality of the SER-001.

So in my opinion the first check would be testing the SER-001 (without
opening the Newt)
Second check would be to watch if the Newt will heat up again.
Next step would be to open the Newt and trying to find the source of the
heat.

Hope this was not too complicated and that it will help.

Johannes

> -----Original Message-----
> From: newtontalk-bounce_at_newtontalk.net
> [mailto:newtontalk-bounce_at_newtontalk.net]On Behalf Of Paul Guyot
> Sent: Thursday, February 14, 2002 9:46 PM
> To: newtontalk_at_newtontalk.net
> Subject: [NTLK] MP2x00 hot in the back: anyone got that problem?
>
>
>
> Hi all,
>
> I've just been having a weird problem. The contrast was low, I
> thought it was badly set and then I handled the Newton and it was
> very hot on the back, under the CPU/SER Board (under the top card,
> right side if you look at the screen).
>
> I removed both cards (the top card was a linear card and the bottom
> card an ethernet card), they were both cold. Then I reinserted the
> linear card so it could deactivate the programs, I unplugged the
> Newton (power and serial cable), removed the battery and open the
> case, a couple of minutes after I noticed it was hot).
>
> The CPU was cold, so was the voyager.
> The SER Board was a little bit hot, just like the case just where the
> board was.
>
> The chips under the board were cold or just a very little bit hot.
>
> Anyone got this problem?
> Could it be SER Board related? (the weird thing is that there is no
> chip on this side of the board).
>
> Could engineer specialists tell me what they think about it?
>
> Anyway, things are back to normal now, but I am quite scared and I
> hope it won't happen again some time at night or when I'm away from
> my Newton.
>
> Paul
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