Epson PX-8. A troubled triple processor CPM laptop from the 1980s. Part #1

Рет қаралды 941

Күн бұрын

Video sponsor: PCBWay: $5 for 2 layer PCBs with 24hr turnaround at pcbway.com/g/m3hn11
In this video we take a look at a very troubled Epson PX-8. This little beauty was quite the laptop back in the 1980s featuring the CPM operating system, a multiline tilt-up LCD, built in microcassette drive and a whopping three processors. We do our best to bring it back to fighting shape in this episode. There are signs of life, but we fall short of getting it booting up. Join us for the trial and tribulations of working on vintage computers.
Timeline:
00:00 - Welcome
02:44 - Disassembly and evaluation
17:14 - Microcassette refurbishment
27:44 - LCD refurbishment
39:39 - Batteries and final assembly
57:57 - Testing 1-2-3
59:06 - Wrap up, next steps
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Пікірлер: 22

@Fezzler61 4 ай бұрын

I know how much patience you need to do these repairs and troubleshooting. But, to have to do them on camera and get good shots takes an enormous effort. Thanks. I know you will get this going!

@iz8dwf 4 ай бұрын

Very nice machine indeed! I look forward to see it running.

@Commodore128Mode3 4 ай бұрын

Most excellent work Jeff. Now I'm on a cliffhanger until your next episode on this unit! What an amazing looking machine! I really hope you're able to get that puppy working again.

@yvairguy 3 ай бұрын

I've got one of these minty fresh in the box still factory wrapped.

@charlesdorval394 4 ай бұрын

Sometimes, it even takes longer... hehehe Good job! :)

@carloporfiri6334 4 ай бұрын

Nice.. i do have two of those!

@NaturalTangent 4 ай бұрын

I've had two of those machines that showed a similar fault. In both cases it was bad RAM.

@SomePeopleCallMeWulfman 4 ай бұрын

I used to have on of these. Unfortunately, it lacked the Wordstar ROM, so its usefulness was somewhat reduced.

@Crashedfiesta 4 ай бұрын

My PX8 has a similar box underneath but it's a memory expansion (which is faulty).. My unit pretends that it's working without the RAM expansion connected i.e. it boots and I can run some apps. I can even use the Oval UD80 display adaptor I have. But the cassette refuses to work. If I issue a cassette drive command from the command line it just fast forwards the tape forever and does nothing else... Glad you noticed the paperclip too! I always thought that was a sign of great engineering. 🙂 Looking forward to part 2! 👍

@DerekWilsonProgrammer 4 ай бұрын

Check the leads from the encoder on the tape drive (the thing that counts the rotations, orange wires) and see what kind of output you're getting. IIRC, it should be around 300hz.

@HeyBirt 4 ай бұрын

You need to format the tape before using it. It keeps an index of the tape contents toward the beginning of the tape. It might be searching for the index marker.

@BrianBrindle 4 ай бұрын

You may have already tried this off camera, but you may need to do a sub-CPU (7508) reset after dead batteries to get it to power up. Power switch off, press the reset button in the option rom compartment then switch back on. Even though it's a switch, it's still software controlled.

@HeyBirt 4 ай бұрын

I tired that but I thought the manual said to switch on, then press the sub-CPU reset. I'll try it the other way.

@BrianBrindle 4 ай бұрын

That likely should have worked too. The power switch just sets pin 23 on the 7508 high or low and it runs it's own ROM routine to power up the device or shut it down. Position is irrelevant. That's how the laptop can power up and down on a timer by itself. The ridiculous, pointless overengineering of this device is one of the reasons it's a favorite.

@DerekWilsonProgrammer 4 ай бұрын

Any thoughts on replacing the battery with an 18650 single cell holder and an MH-CD42? I've done that on my HX-20 and it holds the charge for a long time, several months at least.

@DerekWilsonProgrammer 4 ай бұрын

I got one, same situation as yours, though my capacitors seem ok. Still, turn it on, no beeps, and the contrast does make the lcd get darker. Where did you get that 300mah backup battery? I didn't see the link in the description.

@HeyBirt 4 ай бұрын

Just added the link in description.

@DerekWilsonProgrammer 4 ай бұрын

Thanks, I was going to try a supercap, I still might, just add a diode for the vdrop for charging. The supercap is a 5.5v and with the drop from the diode I can get it to the right voltage. @@HeyBirt

@DavidPlass 4 ай бұрын

Is that foam the same thickness as needed for the NEC PC-8201A? The foam on mine has disintegrated but I wasn't sure how thick it should be.

@HeyBirt 4 ай бұрын

The NEC uses a thicker foam. I did one in video linked below. Link goes to part of video where foam is replaced. The foam I used was 0.25" wide x 0.125" thick. Not sure where I bought it. kzfaq.info/get/bejne/r72lntJl3tnchn0.html

@DavidPlass 4 ай бұрын

@@HeyBirt Thanks. I watched that video recently but didn't remember that it was a different thickness foam.

@HeyBirt 4 ай бұрын

@@DavidPlass I did not remember either. Luckily, I mentioned the size as I did not link to the type of foam used in the description. Probably I picked it up locally.