Saturday, 19 January 2013

PS-SPS250A back to life

Replaced the NPN transistors but no change....

So went further and looked as discrete resistors about the transistors (R5,R6,R7,R8,R9,R10,R12)... one of the 1/2w resistors was open circuit. (R6) Visually did not look like there was a problem. Value was 2.2ohms 1/2W so not one I have normally but I do have 1/4W versions... so I did the parallel/series dodge and using four 2R2 1/4W made up a 2R2 resistor.... I have at least 1/2W capacity and should be fine.

Rebuiilt and plugged in, switched on and supply jumped back into life... :-)

Those transistors are rated at 15A and 25A surge, the power supply is supposed to be 25amp... hum... so I think I'll be careful.

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