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Hitachi SR-903 receiver protection light remains on

I have a Hitachi SR 903 which was working well , with all the provisions given in the Function selector. But lately for the past few months I was using only to connect the TV audio which was working well .
I last used it in working condition about a month ago. I had not used it afterwards for some time.
Today on switching on the Radio, the protection light comes on but does not go away.
I removed all input jacks , speaker out leads etc , yet the protection light remains on
The lights on the front panel , vu meters . signal , FM signal come on when I switch on the radio. All the indicator lights come on when turning the Function switch EXCEPT for
the Auxilary.  The indicator light for Aux does not come on when I select Aux in the Function knob,  Lately I have been using this set only for the TV audio fed into the Aux socket at the back of the set . 

Can you please guide me to get around this problem. 

Thank you. 


torokj picture

Hello Giri,
Schematics is here
The protection circuit switches on when DC level is at the output (with load)
I would check the voltage level at the base of the transistors Q502 /503.
Try to replace the C 502/C 503 capacitors.
Good luck to repair.