IBM 6400-I15 Maintenance Manual - Page 52

to withstand an AC input overvoltage of 300 VAC for one second with no degradation of DC output voltage or damage to printer circuits. DC Power The power supply board contains two DC power supply systems for the printer. The first is a + 5 V bus for logic. The second consists of + 48 V and + 8.5 V buses for the hammer bank and all motors. The + 5 V supply has an isolated return line that connects to the + 48 V return at the printer load. Both returns are tied together in a single-point ground. The + 5 V power supply has its own inverter, separate from the + 48 V and + 8.5 V outputs. There is an opto-isolated input on the power supply that will shut down and latch off the + 48 V and + 8.5 V supplies unless it is pulled up to 5V with a 1K Ω resistor. This resistor is mounted on the controller board and may be pulled down or disconnected by software or internal cable interlocks. The + 5 V output will remain stable for reporting and latching the fault condition. The return for this signal is the + 5 V return. In addition, this shutdown circuit discharges and latches the + 48 V down to a level lower than 15 V in less than 200 milliseconds and requires recycling of the circuit breaker (On/Off switch) to reset the latch. Loss of + 48 V is seen by the EC and reported as a fault. Printer Interface The printer interface is the point where the data line from the host computer plugs into the printer. The printer interface processes all signals and data to and from the host computer. The printer supports supports a number of standard and optional interfaces to the host: ♦ Centronics parallel (standard) ♦ IEEE 1284 parallel (standard) ♦ EIA-232-E serial (standard) ♦ EIA-422-B serial (standard) ♦ Coaxial/twinaxial "Expansion-CT" (optional) ♦ Ethernet10Base-2 or 10Base-T adapter (optional) 52 Principles of Operation