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
    16
    0
    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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