I decided I wanted to pick up an Epson HX20. The fact that it has a built-in dot matrix printer seemed like it would be a pretty cool thing to mess around with.
After a bit of research, I discovered the main issue is that they came with a Ni-Cad battery installed, which usually leaks and causes damage to the computer. But a bad trace or two should be a simple enough fix, right?
So I trawled eBay and found a spares and repair unit for a cheap price. After all, I didn’t want to spend much on a computer that has a high chance of not working. And the majority of these computers are sold as untested or spares and repairs for that very reason.
Well, the device turned up, and upon unpacking it, I could already smell the leaking battery, but this was expected, so I took it apart to check out the LCD board, which normally takes most of the damage. I gave it a quick inspection to see if any damage was visible. And, well, yes, there was some visible damage lol.
From what I could see, a large number of traces were destroyed. So let this be a warning to anyone who is going to take a chance on one of these, if it’s “untested”, this is probably the state of it!
I downloaded the schematics and started testing the connections and marking off which ones were not connected. After a while of doing this, it became apparent that this board was pretty much destroyed. But I didn’t instantly give up (Although I probably should have).
I wanted to try one other thing: could I actually remake the board from scratch? This was a very ambitious project, and I didn’t really hold out much hope, but I think on the first attempt, I actually got a lot further than I expected.
I spent quite some time designing the PCB and re-creating some of the components in Easy EDA, as they weren’t in any of the libraries. The LCD screen for example, needed to be measured precisely and drawn manually.
Eventually, I ended up with this:
I had to manually route quite a lot of the connections, as the auto routers just couldn’t work it out, even on a 4-layer PCB.
But eventually, I ended up with a PCB that said all traces were connected. So I took the plunge and placed an order with JLCPCB. When they arrived, I then had the next challenge of unsoldering all the original parts and re-fitting them to my new PCB.
It was then time to give it a test. Would I see anything? Would lots of smoke pour from the display?
Well, to my surprise, it actually kind of worked. The main issue I had though, was that the alignment and fitment of the LCD screen wasn’t perfect, and I think the pin spacing was also very slightly out.
So, to be fair, I think I did a pretty good job and probably went above and beyond what anyone else would do to try and recover one of these computers.
I have proved that the actual computer itself is working fine, but I didn’t test the printer or tape drive on this unit. Now I have one of the boards made up, which I can directly compare against the original board, I can see some errors that if corrected, may actually get this working again 100%.
The problem is, changing these parts means a complete re-route of all the PCB traces again, which was quite time-consuming the first time around.
For now, I took the coward’s way out and purchased another HX20, which is nearly fully working and the only issue is with the cassette drive, which I think I can handle! I also tested the expansion unit from the old machine and tested it with the new one, so confirmed that it works fine.
So here is the new machine in all it’s glory!
I think I may give the LCD board another go, as it would probably be useful to the community to recover from this common fault on the HX20s. But, I also think I may take a break for a little while first, as my dreams have been haunted by routing PCB traces
