[NTLK] Original MessagePad (OMP) Repair

[Alan Grassia]

Hello Newton Friends,

I recently picked up a Newton MessagePad model number H1000 (1993).  It was an as-is auction, and I was after an inexpensive 9W power adapter and the two game PC cards that came with it (Dell Crossword Puzzles & Other Word Games and Columbo's Mystery Capers).  But I digress.

Upon closer inspection of the H1000, I believe it to be an original MessagePad (OMP).  It will power on, but the screen is glitching/garbled and there is no sound.  Further research in the NewtonTalk archive turned up a post by Frank (https://www.pda-soft.de) from November 2020 (https://marc.info/?l=newtontalk&m=160547481329308&w=2) that describes this issue.  Erik also has a repair video (https://68kmla.org/forums/topic/55600-messagepad-omp-h1000-glitchingflickering-repair/) of an OMP with the same issues that I am seeing with mine.

I know that I very likely need to replace the C1 100uF 4V compact electrolytic capacitor for the speaker and the C51 3.3uF 35V compact electrolytic capacitor for the display.

My question comes down to sourcing the correct replacement capacitors.  You may recall, from my eMate 300 repair, that I don't have any electrical equipment training, so I don't understand descriptors like '100uF 4V' and '3.3uF 35V'.  From doing some research, I understand that if I am using replacement 100uF and 3.3uF capacitors.  I also believe that it is OK if the replacement capacitors have a higher voltage rating, such as a 100uF 25V.  Is that a correct reading of the basic 'rules' for this kind of repair?

I have another question about the type of the capacitors.  If I'm reading things correctly, and I may not be, the original capacitors are compact electrolytic capacitors.  Is there a different type of capacitors that should be used that are less likely to fail?  Some videos refer to Tantalum capacitors (https://en.wikipedia.org/wiki/Tantalum_capacitor).  Do I need to worry about this?

I am considering purchasing an electrolytic capacitor assortment box from Amazon.  While way more pieces than I need for this project, does something like this kit work for what I need?

https://www.amazon.com/OCR-Electrolytic-Capacitor-Assortment-0-1uF−1000uF/dp/B01MSQOX0Q/ref=sr_1_10?dchild=1&keywords=C1+100uF+4V+compact+electrolytic+capacitor&qid=1624808523&sr=8-10#descriptionAndDetails

Any suggestions?



Cheers,

Alan Grassia



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MessagePad 2000, MessagePad 2100, eMate 300



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