The Commodore PET is one of the original “big three” personal computer platforms that launched at the end of the 1970s. Alongside the TRS-80 and the Apple II, they defined three very different approaches to solving personal computing problems for the masses. All three platforms still receive a lot of love, but the PET and its 6502 certainly hold a special place for a lot of people. Tynemouth Software have, contrary to their name, released a whole bunch of hardware over time to support the PET, but just recently we’ve seen a whole series of new items from them, including a dual joystick adapter, an IEEE-488 Diagnostics Tester, video RAM replacements for both the original PET 2001 and the later PET series, and a powerful drop-in diagnostics board that will greatly assist you in fault-finding your PET!
The PET has multiple different pieces that all have to work together for the system to work. All PETs have integrated monitors, so they also have integrated video and CRT power supplies. They also have the main motherboard, with CPU, RAM, ROM, and all the other logic. Then they also have the main power supply and the keyboard. Being able to quickly get an idea of what parts are faulty can save a huge amount of time, and thus the diagnostics board can be a lifesaver. It goes directly into the 6502 slot, so it also eliminates a faulty 6502 from preventing startup. Output is displayed on the screen, so at least that much needs to be working, but having known output sent to the video section can also help troubleshoot any issues in that section.
Another common issue in these older machines is non-working RAM. The video RAM in particular can be very difficult and expensive to come by, so Tynemouth supplies drop-in replacement video RAM modules for the 2001 and the later PETs which use a different RAM chip. The IEEE-488 Diagnostics Board can help find faults not only with the PET but also with attached drives. It shows the current state of the bus with LEDs and also provides a convenient breakout of all signals to make it easy to attach a logic analyzer or oscilloscope!
If you’ve got a PET in need of some love, make sure to check out their full store, which also features other super cool retro computer hardware (including ZX80/81 replica kits)!
