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Table of Contents
SGI Indigo2 Impact Power Supply Repair Notes
Introduction
I recently have had the (dis)pleasure of working on a PSU for an Silicon Graphics Indigo2 Impact workstation. The PSU was manufactured by Zytec, with an SGI part number of 060-8002-001, revision A according to the external sticker. It provides the following rails:
| Voltage (V) | Current (A) | Power (W) |
|---|---|---|
| +5.0 | 40.0 | 200 |
| +3.5 | 36.0 | 126 |
| +3.5 | 12.0 | 42 |
| +12.0 | 4.25 | 51 |
| -12.0 | 0.5 | 6 |
| -5.0 | 0.8 | 4 |
| +5V Standby | 0.1 | 0.5 |
(Total power shall not exceed 385 W)
This power supply differs from the regular Indigo2 supply, as it has an extra 3.5 V supply rail to run the Impact graphics. This rail is broken out via a blue high-current ribbon cable. There is also a small black and yellow twisted sense cable, which must be connected near the power cable on the graphics riser board. If the Impact graphics option is not installed, the termination PCB (mounted on the side of the power supply) must be used to allow the PSU to operate correctly. Without voltage feedback for the Impact rail, it will not work as expected (I have not tested what it does. The rail either will not regulate correctly, or the supply will shut down).
Basic Theory of Operation
(Note: This is far from complete. It is based off my limited experience repairing one of these supplies, as well as my own research. I will attempt to cite any sources I used.)