My Epson HX-20 is now back in one piece, and - look - no wires! It's running off internal capacitors (more in a moment...). I'd replaced most of the caps on the board - which got the LCD useable, and allowed it to run off less than 5v input at the battery terminals.
#retrocomputing
🧵 1/n
In place of the internal battery I've put 6x 10F capacitors, wired as 3 paralell x (2 series) - so 30F at 5.4v. That lets me run for about 10 minutes mostly idle when fully charged. Now, the fully charged is hmm...so I replaced D2 by a lower drop diode (about 0.4v rather than the 0.7v it had) and that lets me charge those caps fully with 5.7-5.8v input; I can -just- about maintain the battery at 5.0v in, but it certainly needs the 5.7v for the printer. A lower drop diode would be nice.
🧵 2/n
I bet there's actually room in there for say 4x25F or even maybe 4x100F if you can find the right size:
🧵 3/n
And here's my trick to make sure all the screws went back - in cardboard, and labelled!
🧵 4/4
penguin42
Jim MacArthur
David Sullivan
Maicon Pinheiro