Epson PX-8 / Geneva repair

[PixelTheCat]

I just got a PX-8 with a 120kb ram wedge advertised as 'untested'; it actually does boot up with power at the jack, although not reliably. Of course, the batteries are original. I don't see any leakage or corrosion on the board. Using the Leeeeroy Jenkins technique, I clipped the main battery lead and attached to some wire I snaked through the ribbon cable opening, and then soldered this to a 18650 battery board with 5v output (https://www.amazon.com/dp/B0CNK896J2?ref_=ppx_hzsearch_conn_dt_b_fed_asin_title_1&th=1). It powers up fine, but the battery doesn't last long even with the computer on standby (at least not overnight); I suspect there may be more draw to try charging the no-doubt dead backup battery, and the battery board has lights that stay on which also doen't help. I've a most likely better power board from Adafruit on the way that allows charging a battery while also supplying power; again my plan is to install without any permanent mods to the PX-8 itself.

I'm a little suspicious of the power supply portion of the PX-8; while the capacitors look ok, the green large resistor had melted into the case just a bit prior to my receiving the unit.

 

[spiderx]

There's a switch for the battery and some jumpers you can set which will set for 'overcharge' but it shouldn't draw much power. There's a thermistor which controls how often the dram refreshes, that might be damaged which would make it constantly refresh the ram.