Oh boy, the Epson HX-20 is poorly.

[rubber_jonnie]

Great, why does stuff suddenly die like this!!

So the HX-20 has a weird system, whereby the power comes from the battery, and you don't run the machine from mains power, rather the PSU charges the battery and the machine runs from battery only.

Well something weird is going on, because it won't power on, but the battery doesn't seem to charge, well unless it is already fully charged(I have my doubts based on when I last charged it), as it's only pulling 10-15ma when charging via a bench PSU configured as per the HX-20 specs.

I suppose the battery could be bad, but need to start digging deeper.

This is a project I really didn't want.

[PhilC]

@rubber_jonnie oh hard luck with that RJ.

Sounds like another learning opportunity. Reminds me of a MacBook Pro that wouldn’t charge one day but would the next.

[stephen_usher]

Can you clip leads onto the battery terminals and power from a bench power supply as a test?

[rubber_jonnie]

@rubber_jonnie oh hard luck with that RJ.

Sounds like another learning opportunity. Reminds me of a MacBook Pro that wouldn’t charge one day but would the next.

Have managed to get the technical manual downloaded, so that's a start.

[rubber_jonnie]

Can you clip leads onto the battery terminals and power from a bench power supply as a test?

I have indeed, though I will revisit, it's barely drawing anything, less than 100ma when powered on. I need to look at how the battery powers it. Of course that may be totally normal for this machine.

I am getting 5v to most ICs, but the best the display will do is flicker, though it does beep on power up, which is slightly encouraging.

What makes this one hard is that it's dual CPU and virtually no 74LS ICs, it's all kinda weird. I think if I can figure out power to begin with, that would be a good place to start, as I'm not 100% convinced it's right, and the weird symptoms are very similar to a low battery.

[rubber_jonnie]

So, minor update, I decided to reassemble the machine as it has a lot of internal shielding and it looks like their may be a connection between all the boards on GND.

And it kind of worked, i got the display and menu up, but later it went off piste again.

So I have been looking into the tech manual and it's a nightmare with all the functions broken down into sections and no master schematic!!

This may take some time!

[PeckPeekPoke]

Good luck reviving that old HX-20. It'll be really cool to bring to the beach when it runs. Here is some hopefully useful info:
https://fjkraan.home.xs4all.nl/comp/hx20/index.html

[rubber_jonnie]

Good luck reviving that old HX-20. It'll be really cool to bring to the beach when it runs. Here is some hopefully useful info:
https://fjkraan.home.xs4all.nl/comp/hx20/index.html

I'm sure the problem is something minor since it did power up properly once today. Thanks for the link, looks like an interesting resource.