Task: Perform a Dead Test on a Non-Working Commodore 64 Computer
Needed: Dead Test Cartridge or Program, Commodore 64
Time: 10-15 minutes
Introduction
I have previously posted about using the Diagnostic Test to troubleshoot a non-working Commodore 64. However, there are a number of faults that can prevent this test from running. For example, a bad SID or CIA chip can bring down the entire system if it creates a conflict on the data bus. The Dead Test was created to get around this problem by only using the CPU, PLA, and VIC-II chips to boot and run the checks. In fact, you can remove the CIAs, ROMs, and SID completely and still run the dead test. This is a good thing to try as any one of those chips could bring down the entire system and prevent the dead test from running. Also, it is important to note that it is not perfect and can lead you astray. However, it can provide some clues for diagnosis when used in combination with the awesome pictorial fault guide that allows you to match what you are seeing (or not) on the screen.
Instructions
There are two easy ways to use this dead test. First, you can purchase a pre-made cartridge online for about $25 to $50. These are available from multiple sources including eBay. I purchased this one for $30 that included both the dead test and the diagnostic test. This one also came with a nice 3D-printed case making it convenient to use. I later made some and have them for sale on my own Etsy store for $30. Other sources include this one from Retro Rewind and Core i64. Second, you can download the binary file and place it on an SD-card device such as the Kung Fu Flash. I confirmed this works great. The main version circulating is 781220. There is a ++ version that extends to some other Commodore models.
Before you perform the test, you should take a look at the instruction manual. There are a lot of good tips for what to expect and how to interpret the results. You might also watch this informative YouTube video from The Retro Channel.
To run the test, simply boot your C64 with the dead test cartridge plugged in or select and run the program from the Kung Fu Flash or similar SD-card device. The test will start automatically and cycle through each of the checks.
Note that the BAD results shown above are because I do not have a diagnostic test harness plugged in that sends the right signals from the various ports back to the cartridge. I will do a post about these when I decide to purchase one. You can test these ports manually by hooking up joysticks or a cassette drive and manually testing them.
Comments
A very useful device and worth getting if you have multiple C64s or plan to do repairs.