Heathkit ET-3400 Part 1: Designing and building an ETA-3400 Memory/IO Accessory 

My grandpa gave me one of these and also the digital electronics trainer when I was a teenager. He had built them in the 70s. The microprocessor one didn't work but it was probably the first electronics thing that I ever fixed and it was so exciting when I narrowed it down to one of the logic chips using the assembly manual (they were so good!), replaced it, turned it on and the leds said CPU UP. Unfortunately when we moved at some point my mom made me throw out a bunch of stuff and the Heathkits went in the garbage. :(

My father had one when I was a child and my fondest memories are of him building these kits; in my mind, he was a genius. I have all of his kits now and this has just find its way to my to-do list cause I know it's a project that would have been right up his alley. Thank you so much for making it public.

I looked over the Heathkit catalogs as a teenager. We used them in Electronics Eng course in community college, 1987-89. Great throwback and fond memories. Really enjoyed those years.

I like the "10-key" style layout of the keypad

How cool! I’ve been working my way through “How to Program and Interface the 6800” by Andrew Staugaard, which references experiments with the ET3400 and the Motorola MEK6800D2. Neat to see the Heath model explained!

Good trick with the magnets for binding the expansion to the unit.

I learned assembly/machine language using one of these units in college. I periodically look at them on eBay. Good memories.

that ETA-3400 Memory I/O Accessory is very nicely designed and executed. I'm interested in making one now, but with no 3D printer I may have to find someone else to make it.

I have a heathkit et3400 and this is EXACTLY what I needed

I always wanted a HEATHKIT E3400 trainer. Funny, i had been working with a dozen different Micros at Boeing back in the late 70's and early 80's, but I still wanted one...

That's too cool, I have one from EBay coming also! The + & - 12V was used for a 741 opamp input for one of the experiments

Fantastic Demo... I have one too In my heathkit collection.

I remember using these at college in the mid 80s and being really pleased because I'd wanted to get my hands on a "hex keypad computer" for ages... I don't know about running BASIC on it is "right". Forth might be OK but BASIC seems somehow "sinful" ;)

Anyone else notice that the thumbnail says the video is an hour long yet in player says 42 minutes?

If you could write to the eeprom just like ram. You could write the programs to the eeprom and build your own toolbox of routines.

I am building the kit on one of your boards. I am new to the Pi, do I install the basic software (some version of Linux) and then run the Pi scripts on your Github folder? Great project, thanks

Here is IC that came with the Kit from CiE home study course 14-B in 1977. You need to get it and also MC6820P I bought two of these, I got one in 1977 and one just last week, November od 2020

Good day, I have built the Expander. I can't seem to get it to run. I think it is the programming of the f16v8b. What file do I use to in the rom programmer? Thank you

my house electricity is 240v, and the device is 120v, what to do? help me.

Good show....What 3d printer are you using? I am looking for something with a larger bed than my 6 x 6" Thanks !

would you consider to sell your version of the ETA-3400 as a kit including the PCB, the 3D parts and the electronic parts?

that is pretty cool. I almost bought one last year but the price was too rich.

That flipchart is cool. I'm going to have to search for a pdf on the web.

Scott, you did not mention where you obtained the code for the expansion EPROM........? I would offer a correction on your statement about "as high level as BASIC gets".....the original product had only a 'tiny BASIC', so far from full featured. I don't necessarily recall all the differences between the ET-3400 and the ET-3400A, but I have owned both at different times, and I thought the main difference was that the ET-3400 used a 6800 CPU while the ET-3400A used as 6802 or one of the variants that had 256 bytes of RAM built into the CPU....to the ET-3400A PCB had sockets for only two RAM chips because the other 256 Bytes was in the CPU. Seems like they might have used a different keypad as well, although both versions had pretty nice keypads, far better than practically any other single board computer of that era.

Nice video. I found an ET-3400 fold-out schematic in my collection. Since I sold my ET-3400, I have no use for it. Let me know if you would like it mailed to you.

Good thing you didn't need the serial IO inversion, the Rx inverter is facing the wrong way. Surprised that you didn't also include the likes of an FTDI module to give serial IO on a USB socket as an option rather than the DB25. Something like www.aliexpress.com/item/1005001303615156.html with its right angle connector removed and a straight connector installed from below linking it to your PCB.

I have six of these and some others brand new in the box never put together with all the papers. Contact me I seen your ebay listing