28-05-2013, 07:40 AM
(This post was last modified: 28-05-2013, 07:43 AM by Old Sparky.)
A summary of the results of my tests so far follows.
With no mains transformer connected and the two 4A(T)secondary fuses removed, I applied power from my single rail PSU(I can actually wind it up to 27v!) across the +ve & -ve lines. With respect to '0'v I measured +12 and -17v. Disconnecting the collectors of the SAP15Ns made no difference ( I assumed something was loading the +ve rail), but disconnecting the collectors of the SAP15Ps restored the equilibrium. I now measure +13.5 & -13.5v WRT 0v. Quiescent Current consumption at these voltages is <20mA regardless of whether the o/p transistor collectors are connected or not. Would I be right in suspecting the SAP15N &/or SAP15P devices from the above tests, admittedly being carried out at 30% of the supply voltage normally used? I am still puzzled by the fact that none of the 4Amp fuses had failed, and that no component I tested(o/p devices and smoothing capacitors mainly) checked faulty.
With no mains transformer connected and the two 4A(T)secondary fuses removed, I applied power from my single rail PSU(I can actually wind it up to 27v!) across the +ve & -ve lines. With respect to '0'v I measured +12 and -17v. Disconnecting the collectors of the SAP15Ns made no difference ( I assumed something was loading the +ve rail), but disconnecting the collectors of the SAP15Ps restored the equilibrium. I now measure +13.5 & -13.5v WRT 0v. Quiescent Current consumption at these voltages is <20mA regardless of whether the o/p transistor collectors are connected or not. Would I be right in suspecting the SAP15N &/or SAP15P devices from the above tests, admittedly being carried out at 30% of the supply voltage normally used? I am still puzzled by the fact that none of the 4Amp fuses had failed, and that no component I tested(o/p devices and smoothing capacitors mainly) checked faulty.
