retrohax.net

… or Egyptian adventure

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Story

For the past few days, I am battling a sinus infection and I cannot work in my garage so I’ve decided to write some blog posts. This is going to be another “old story” post. I took pics for this post back in mid-2020 🙂

The story is quite usual, a friend of mine asked me to search for a specific computer for him – Enterprise 64.

After reading some forum posts on Polish and Hungarian forums, I found out, that these computers were popular in UK, Hungary, and Egypt. I was surprised to find NOS units in Egypt. Well, at least according to the eBay seller. The problem was that shipping costs were kinda high. Sachy/Lamers came up with an idea and suggested that some folks from the local retro community might want to have such a machine so we could order more computers and split shipping costs. He was right and that significantly lowered shipping costs per person.

A couple of weeks later four machines showed up, YAY! 🙂

EP64 #1

In general, these computers were in very good shape, however, they needed cleaning as some weird polymer reaction was visible on a joypad. Below, is the first machine that I’ve worked on.

Apart from that, loose parts were rattling inside. The plan was to disassemble it, clean and check what was wrong with loose parts before powering it on. It turned out that the copper heatsink got loose inside one of the machines.

Now, I could move on to testing but first I needed a proper A/V cable. I had to make it myself as it is not a standard one.

EP64 uses an edge connector for video output so I had to improvise a bit. I’ve cut an old PC ISA connector into pieces and cleaned them afterward.

Fits nicely.

I’ve found schematics for this cable on one of the Hungarian websites. Here it is just in case you need it.

I’ve connected the video cable and it worked right away!

The first machine was ready. I will get back to it later and now let’s fix the second unit.

EP64 #2

It wasn’t that easy with the second machine. It required cleaning and some electronic fixing. It was missing a joy cap and a side connector cover but these were easily 3D printed 😉

Unfortunately, this EP64 produced garbled video output.

After researching this issue, I’ve figured out that one of the transistors is to blame. I’ve ordered a replacement transistor – BC337 – which is a standard bipolar NPN transistor. Replacing it, fixed the issue.

Fixing a broken keyboard membrane was next on the list. It became very brittle because of its age so first I had to cut it. However, after cutting it, I had to extend it somehow because it was simply too short to reach the connector on the motherboard. I’ve decided to desolder the original connector and extend it with a ribbon wire. I’ve also added a piece of plastic to the membrane to strengthen it.

Upgrades

I’ve started looking for upgrades on Hungarian Enterprise 64 forums. By the way, these forums rock! Very informative source. It quickly turned out that one of the guys still manufactures various add-ons. Funnily enough, it also turned out that he is my fellow countryman who is also a member of speccy.pl community. Pear, as it is his nick, created several cool expansions. I’ve contacted him and ordered some of them. I don’t have links to every single mod though.

• EnterMice – PS/2 mouse and joystick interface
• EXDOS – Floppy drive interface
• BusBridge
• IsBasic cartridge
• ZX Spectrum emulator card
• RAM expansion card – original

Add-ons came in quickly and some with nice 3D printed cases.

IsBasic cart worked right away.

I’ve 3D printed a case for EXDOS and added a GOTEK drive to it which I’ve modded with an OLED display.

Next, I connected a ZX Spectrum emulator card via a BusBridge. Unfortunately, as I’ve quickly found out, it requires more RAM, so I had to install a RAM card first.

The end

This is all I’ve for now. However, our Brazilian friend donated a very nice Enterprise 128 machine that I will be working on soon. Hopefully, it won’t have to wait another two years for its blog post 😉