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Hi all, Update: Symptom: No display in HP8593A with low supply rail (+5V) after initial power up. I tested the power supply on bench with 2.5A load on +5V, 0.8A each on +/- 15V. The power supply was up and running fine. Short Pin 19 with 17 to bring on PS. There was no fault in any of the electrolytics. So prepared Power supply extension cable (1 mtr length) ?for the 37 pin D-connector as it was not feasible to test the voltages on pins. And voila!! the spectrum was up and running. I switched it off and on several times to confirm the power supply was not in fault. The HPWRUP signal from power supply(Pin 37) to Controller board feeds 74HC14 gate and o/p is again inverted by 2-i/p distinct nand gates to obtain LRST and LHLT signals to the processor. When the CPU is halted the current drawn falls below the PS required threshold and hence the PS stops regulating. 1. It was the Power supply unit connector fault and several attempts were made to onstall the P/S but the result was not consistent sometimes the SA would come ON and some times not. There was loose connection in the mating 37-pin D-connectors. The D-connector on the P/S unit mounting was then bent outwards by about 2mm to ensure proper mating, but then that lost flexibility of adjusting the connectors mating. The Connector on the Power supply can move about 3-4mm sideways to ensure the mating on the main board. That was not a problem as once installed there is no need to move the power supply again till it fails. Line trigger is the signal used by the SA in its trigger function. Thanks for the one who made the circuit schematic available of the board. Thanks Roumen for the schematic of Power supply. Thanks for your inputs. Regards, Kailash Khairnar On Sun, Jan 31, 2016 at 9:48 AM, AMiTHA <amitha.my@...> wrote:
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