Editing IBM 3270 PC/G (section)

== Common Faults ==

The PC/G inherits all of the chassis-level faults of the [[IBM 3270 PC]] (RIFA mains-suppression caps in the PSU; tantalum bypass shorts on the planar; ageing 130 W IBM XT PSU). PC/G-specific faults:

* '''IBM 5278 Display Attachment Unit''' — separate enclosure with its own PSU and active vector-graphics circuitry. This is '''the rarest single component in the PC/G system''' after 40+ years and is the most likely failure point. The 5278 is not interchangeable between PC/G and PC/GX configurations (the /GX uses the larger 5378).
* '''IBM 5279 14" colour CRT''' — dedicated tube and timings; failure means substituting an IBM 5151 monochrome display (losing all graphics modes) is the only practical recovery.
* '''75-pin cable''' between 5278 and 5279 — proprietary; can develop intermittent contact at the connectors.
* '''GCP system diskettes''' are rare in 2024; image them immediately if you have a working installation.