Needs help on understanding the operation of this schematic.

Discussion in 'General Electronics Chat' started by opa627bm, Apr 2, 2015.

  1. opa627bm

    Thread Starter New Member

    Nov 26, 2011
    Hi all,
    I have bought this power supply from a local auction and found out the reference was bad. After inspection, I realized that the thermostat in the oven assembly was bad and over cooked everything inside. I have attached the schematic. I am going to replace the +ref and -ref with LM399 and LT1001. But I am having trouble understanding the operation of the diff pair. Why they are biased differently. Why Q5B collector is connected to virtual ground but Q5A is connected to VG+Vref.
    Any inputs will be highly appreciated !
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