K4005b and K4006

I just assemble the kit K4005b with power supply K4006; to turn ON a very low volume delivery …
(amplifying starts well but to take a few seconds down …)

IC2 leg 5 is 30 volts. I’m not using (TS) thermal protection.
They set up stereo, 950mV input sensitivity.
Transformer + - 24 V AC. Delivery K4006 + -36 V DC.
Any ideas that can help me to find the error?

thanks in advance !!!