[NTLK] MessagePad 100 (OMP H1000) Flickering/glitching screen, no/low sound fix

Erik Johnson apple.newton at retro.network
Wed Oct 3 17:47:36 EDT 2018

I recently purchased a defective Original MessagePad for a good price 
hoping to fix it blindly.  And I did; 2 compact electrolytic capacitors 
inside had leaked and gone bad, there are 3 in total inside the device 
but 1 is not the typical compact/surface-mount kind that goes bad and 
can probably be ignored safely for now.
Symptoms?  On power-up the screen is garbled and glitches terribly with 
occasional flickers of the newton logo and eventually sometimes showing 
calibration text/crosses - but mostly just random lines and black bars.  
Also no start-up chime.

When first removing the back cover C1 had a white fog around it, it's a 
surface mount and is located right next to the speaker wires.  Original 
value is 100uF @ 4V.  I only had 100uF @ 25V on hand with a slightly 
larger 6.4mm diameter body and it fit fine. After cleaning the residue 
off with isopropyl alcohol and replacing this I got sound - a start-up 
chime!  But the video was still broken.

All the other capacitors visible are tantalum solid-state caps and 
should be fine.  Plus one obvious through-hole cap that isn't the 
compact type to go bad, typically.

So I removed the logic board itself to have a look at the other side; 
and lo!  One more surface-mount electrolytic not too far from the 
display ribbon also with residue around it.  C51, valued 3.3uF @ 35V.  I 
had 3.3uF @ 50V on hand.  Clean and replace.  Reassemble. And I have a 
beautiful working OMP now.  Useless handwriting recognition and all.

Pictures here https://imgur.com/a/69J7YWl

- Erik

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