Measurement/Searching techniques/Experiment Introduction Damage was first identified in a couple of surface mounted diodes, see Figure 2.10-2 below, which are near the switch mode power supply connector. Miti(08)_F2.10-2 Figure 2.10-2 – Picture of damaged diode Circuits, schematics and printed circuit board (PCB) layouts were obtained for this part of the system. This information, in combination with installation documentation, enabled a scenario for damage to be determined. It also identified components likely to be damaged. These components were: – a thyristor protection circuit, which is a switching type protector and the first component on the printed circuit board where the line terminates; – a diode which clamps the incoming line to the –70 V supply rail (line); – a diode which clamps the incoming line to the –35 V rail (line); – two diodes which connect from the –35 V and –70 V supply lines to the SLIC circuit. One of these diodes is shown damaged in Figure 2.10-2 above; – the SLIC circuit. Case study 2.10 – 2 –