The Boards

Testing the Chad’s Arcade Defender Memory High Score Save Chip

Our very nice friends at Chads Arcade sent over a couple of their Defender High Score save chips so that I could test them on our Defender machines at Skywire And these kits are great – replacing the need to have the 3 x AA batteries, or CR2032 battery conversions on the main motherboard by…

Testing the 4116 memory

One of the questions asked quite a lot with Williams boards is how to test the often failing 4116 memory chips Well the good news is that the 4116 shares the same 100% compatibility with the NEC D416C-2 4116 16Kx1 RAM chip, which was used on the ZX Spectrum Here’s a nice picture for reference…

Upgrading: Replacing the 4116 memory with 4164 memory

It’s a well documented fact that the standard 4116 memory used for the Williams games such as Defender gets very hot and fails often, and also requires multiple voltages to work, which make them a hassle to maintain One common upgrade is to replace the 4116 memory (64k memory needing +5V, -5V and +12V) with…

Defender ROM Versions – The history

One of the cool things about spending a lot of time learning how to rebuild the Defender machine, is that you soon build up a fair amount of knowledge about how it works and the history behind it. So I recently updated a post on KLOV with the correct information about the 3 different production…

Testing: Building a Williams Test Rig (part 2 – interchangeable power supplies)

In order to keep the Williams Defender harness I have as original as possible, I don’t want to replace any of the original connectors so instead we are going to make the linear PSU and the original Williams PSU totally switchable using connectors. 1. Acquire male and female ATX connectors The number of wires used,…

Testing: Building a Williams Test Rig (part 1 – board layout)

In order to test our Williams CPU, ROM, I/O and Sound boards I’ve decided it’s time to invest some time and effort and build a complete Williams Test Rig. The goals of the rig are: – Allow testing of all Williams boards (CPU, ROM, I/O, Sound) – Allow testing of all Williams games (Defender, Stargate,…

Testing: Building a sound board test rig (part 2 – with video :-) )

So we have the sound board correctly powered with +5V, +12V and -5V, speaker connected and volume control turned up, so the final task is to simulate sound triggering from the CPU by grounding some of the input pins on IOJ3 (top right of sound board) from 2 to 8 (1 is key and 9…

Testing: How to basically test your Defender board set

From a post I wrote on UKVac to hopefully help another user “Is anyone on here able to test my defender boardset for me? It shows lines down the screen and has never booted properly and the old owner said the sound had failed before I bought it.” The sound board and the interface boards…

Testing: Building a sound board test rig (part 1)

So.. we need sound and I need a way of testing the boards I have to see if they work, but actually switching them in and out of the main Defender cabinet is a really slow process. Therefore – let’s build a sound board test rig and we can go through all the boards we…

The Boards: Repairing the sound board

Interestingly the sound boards for the Williams machines of this era, are basically stand-alone mini-computers that are just triggered with which sound to play, by the main CPU board. Think of it kind of like a door-bell, where you can press different buttons to get different sounds as you go down the street. So I…

The Boards: Defender is Alive!

So I decided that without a working set of a Defender boards it was going to be impossible to progress the machine further, as not having any control test for the boards we have meant that guess work and luck was about the best we could hope for. So I got in touch with a…