Case 346532. 02/12/24 Pioneer SX-780. Makes loud pop sound after turn on and relay clicks 2-3 times. Sound is ok.
Bad capacitor 33ufx16v next to protection relay.
After closer look found oxidation on protection relay contacts. Cleaning doesn’t help for long run. Relay replacement solved the problem permanently.
Used this relay
After troubleshooting using ” freeze spray ” for transistors method found 2 transistors 2SA726 in right channel driver board acting bad after cold application . All unit transistors 2SA726 changed to 2SA992 . They have same look but different pinout. Pay attention ! 2SA992 / KSA992 is better in parameters and performance.