Epson HX-20 - Collective brain help required :)

[rubber_jonnie]

Well this just arrived, I'm hoping it isn't dead and I can use it as a reference for my other dead one!!! Or I can at least make one good one out of the two machines!!!

IMG20260428120249.jpg

I have to say delivery was super quick on this.

[HigashiJun]

Fingers crossed !

[rubber_jonnie]

Fingers crossed !

First thing I think is to pull the battery and see what's what.

[rubber_jonnie]

OK, so old battery out:

IMG20260428133113.jpg

And whilst it looks OK, under the red heat shrink there are strong indications that the battery cans are corroded. Also, rebuilt battery is showing signs of life at about 3.5v and this one shows zero...

No damage to the mainboard though which is good.

I have been charging my pack via the original HX-20 and it charges at about 50mA, but only at about 11mA on the new machine. So I will leave it all afternoon and see what happens.

It is possible I have a dead cell in my rebuilt pack, I built it a long time ago, but we'll wait and see.

However there was just enough power for me to see that the new machine does boot!! It beeps and shows me the CTRL and @ to initialise prompt, so I am hopeful that with a good battery it will run.

However the 'good battery' statement is important because the power supply doesn't power the HX-20, it just chatges the battery, so if I have a bad battery pack I'll need to build a fresh one. Wondering if I can use some spare 18650's..

[PhilC]

What batteries are in them? Look like four cells.

[rubber_jonnie]

What batteries are in them? Look like four cells.

There are indeed 4 cells. My replacement pack used ESP1700SCS 1700mAH Ni-Cad cells:

IMG20260428134225.jpg

Will see about getting some more, they are 1.2v cells.

[stephen_usher]

What batteries are in them? Look like four cells.

I found a like-for-like replacement on-line for mine. I’ll see if I can find where I got it.

Note that the charging system is very crude, just using a resistor and crossing fingers

[rubber_jonnie]

I found a like-for-like replacement on-line for mine. I’ll see if I can find where I got it.

Thanks. I have some cells on order but may have to opt for a pre-made item.

Note that the charging system is very crude, just using a resistor and crossing fingers

Yeah I remember!

Also it doesn't run off the charger and requires the battery to be charged IIRC.

[stephen_usher]

Also it doesn't run off the charger and requires the battery to be charged IIRC.

Indeed, like many systems of its age.

[rubber_jonnie]

Also it doesn't run off the charger and requires the battery to be charged IIRC.

Indeed, like many systems of its age.

Quite.

Annoyingly I'm in the office today so not much happening with this.