Troubleshooting the IBM 5170 Motherboard: A Journey into Retro Repair

In the fascinating world of vintage computing, there’s always a new challenge waiting for enthusiasts. Today, we find ourselves diving into the intricacies of the IBM 5170 motherboard, specifically the 1985 variant. This particular unit has shown promise, yet it’s not quite reaching full functionality, and I’m determined to uncover the root of the problem.

Upon examining the motherboard, I discovered a significant issue with one of the chips—an Allen Bradley 316A103. The corrosion surrounding all 16 pins is particularly concerning and seems to be a likely culprit behind the motherboard’s failure to complete the Power-On Self-Test (POST). However, there’s a question that lingers: the second number on this chip—8642. What does it signify? Could it be a revision number, or something entirely different?

While researching potential replacements, I’ve noticed that the same chip appears for sale online, but curiously, the four-digit numbers often vary, with examples like 8515 cropping up. This inconsistency leaves me wondering about compatibility and the implications of these numbers on the repair process.

Currently, I’m equipped with a POST code reader, which should offer valuable insights. As of now, the board seems to initiate the POST process but falls short of initializing the video components. Interestingly, there are no audible beeps to indicate errors—a point that adds to my intrigue. The front panel light is operational, and the power supply remains engaged without automatic shutdown until I manually switch it off. I’ve ensured that most components are disconnected, keeping only a Persyst Mono 2 card, front panel lights, the speaker, and the battery for testing purposes.

As I proceed with the repair, I’ll keep you updated on my progress, and hopefully, I can breathe new life into this classic piece of technology. If you have any advice or insights about the peculiarities of the IBM 5170 or the Allen Bradley chip, please feel free to share your thoughts in the comments below! Let’s embark on this retro repair adventure together.