So far I’ve been able to test the 6510 CPU using a NOP tester circuit on a breadboard, the 4164 DRAM chips using a £20 Arduino-based DRAM tester by Stephen Vickers, and the logic chips using my trusty TL866II+ EPROM programmer. Which got me thinking. Is there an easy way to test whether the PLA I’d removed from my C64 was working or not. Like the MOS logic chips, these have a reputation for failing. …
In the previous post I’d checked the DRAM and the MOS logic chips, some of which are responsible for memory decoding. The RAM was fine, and one of the logic chips had failed. I was, however, still seeing what looked like an anomalous signal on some of the address lines. I couldn’t think of an easy way to diagnose the 6510 CPU in situ, so decided to desolder it from the motherboard and test on …
Following on from the previous post where I’d removed the SID and desoldered the PLA, and with a Commodore 64 that was still exhibiting a fault, I moved onto the next stage of the diagnostics, removing and testing the DRAM. This was a fairly straightforward task, and mostly covered in the video. At the end, it appeared that I was still having issues with the address lines on the CPU, so the next stage was …
