IBM PCjr Capacitor Replacement Guide: Difference between revisions
Add the PCjr internal teardown photograph alongside the power supply description |
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== How the PCjr is powered == | == How the PCjr is powered == | ||
The PCjr uses what IBM calls a '''two-stage''' supply, and what it does is split in an unusual way:<ref name="tr">IBM, ''IBM PCjr Technical Reference'', "System Power Supply" and its Operating Characteristics, Over-Voltage/Over-Current Protection and Connector Specifications subsections. Source for the two-stage 33 W description, the transformer's short-circuit-protected extra-low ac output, the internal Power Board that converts that ac to three dc levels, the three dc rails and their regulation tolerances and load currents, the +5 V minimum load required for −6 V to be present, the input requirements, the transformer connector pinout, and the input and output protection tables. Hosted on this wiki as [[:File:IBM PCjr Technical Reference.pdf]].</ref> | The PCjr uses what IBM calls a '''two-stage''' supply, and what it does is split in an unusual way:<ref name="tr">IBM, ''IBM PCjr Technical Reference'', "System Power Supply" and its Operating Characteristics, Over-Voltage/Over-Current Protection and Connector Specifications subsections. Source for the two-stage 33 W description, the transformer's short-circuit-protected extra-low ac output, the internal Power Board that converts that ac to three dc levels, the three dc rails and their regulation tolerances and load currents, the +5 V minimum load required for −6 V to be present, the input requirements, the transformer connector pinout, and the input and output protection tables. Hosted on this wiki as [[IBM PCjr Technical Reference]] ([[:File:IBM PCjr Technical Reference.pdf|PDF]]).</ref> | ||
* '''Stage one is the external "brick" — and it is a transformer, nothing more.''' It steps mains down to a short-circuit-protected, extra-low '''ac''' voltage. IBM's connector specification for its output reads "Pin 1 – 17 Vac, Pin 2 – GND, Pin 3 – 17 Vac". There is no rectifier, no switching regulator and no high-voltage bulk capacitor inside it. Its mains cord is 3.08 m (10.16 ft) long.<ref name="tr" /> | * '''Stage one is the external "brick" — and it is a transformer, nothing more.''' It steps mains down to a short-circuit-protected, extra-low '''ac''' voltage. IBM's connector specification for its output reads "Pin 1 – 17 Vac, Pin 2 – GND, Pin 3 – 17 Vac". There is no rectifier, no switching regulator and no high-voltage bulk capacitor inside it. Its mains cord is 3.08 m (10.16 ft) long.<ref name="tr" /> | ||