The switch mode preregulator should hold a ~3.5V difference across Q9. To verify this lift the end of R9 that is connected to Q9. Put aload of 500 ohm 10W across C5. Disconnect Q9 collector. Power up.The voltage on C5 should now be about 3.5V. If it is, the preregulator is ok. Tracking can be verified by connecting an external (isolated) supply between the disconnected end of R9 and output negative. The voltage on C5 should track the power supply plus ~3.5V
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