Sansui Au 777 has suddenly gone into protector mode. Have disconnected everything and retried connections. Speakers are humming when powered back on.

Help and a repair video in the link

https://www.google.com/search?q=Sansui+AU-G77X+Amplifier.+Protection+light+blinking

..

Hello, please check/replace the relais. If you need more info please advice. Arpi

Hello Bernard, for your description of the fault, the Sansui AU-33 team, has problems in the output stage of speakers or in the power supply stage, you should go to a specialized technical service

Hola Bernard, por tu descripcion de la falla, el equipo Sansui AU-33, tiene problemas en la etapa de salida de parlantes o en la etapa de fuente de alimentacion, deberias concurrir a un servicio tecnico especializado

If the speaker protection is activated then this would indicate that either a dc voltage is appearing across the speakers or a short circuit on one or more speaker cables. Since you are able to get normal sound through the headphone function the former is less likely and you should check for a possible shorting speaker cable. Another possible cause for the symptoms can be dry joints on the speaker protection relays.
regards from Vintie

see this instruction and fix it. God bless you

1. • 1
     Disconnect the coaxial cable at the back of the satellite receiver or cable box by unscrewing the coupler on the cable end.
     
     
   • 2
     Attach the cable to the RF IN jack on a surge protector and tighten the coupler clockwise.
     
     
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   • 3
     Connect a second coaxial cable from the RF OUT jack on the surge protector to the input on the cable box or satellite receiver. If this stops the hum, congratulations: You're done.
     
     
   • 4
     Unplug the subwoofer's electrical cord from the power strip or wall outlet if it is connected to the same circuit as the AV receiver. The amp in the AV receiver and the amp in the subwoofer are in conflict over the grounding of the electrical circuit.
     
     
   • 5
     Plug the subwoofer into its own surge protector and connect the surge protector to a different wall outlet than the AV receiver uses.
     
     
   • 6
     Disconnect the subwoofer cable from the back of the sub and the AV receiver if all other measures fail to stop the humming. Reverse the plug connections so the plug that had been connected to the receiver is now connected to the subwoofer. Turning the cable around may solve a problem known as ground-loop hum by reversing the shielding wire inside the cable.
     
     

Read more: http://www.ehow.com/how_6979184_eliminate-sound-home-theater-subwoofer.html#ixzz2ZdzrgBSa

do they hum when you unplug the audio jack from the PC?
If they stop humming when disconnected the problem will be down to a bad earth connection on the motherboard, or a failing power supply (rectifier circuit)
Humming is normally a result of voltage potential and the 50hz frequency in the mains.

Hope this helps

the transformer that converts that converts AC to 12v DC might have gone bad... check for the connectivity...

Disconnect all speakers at the receiver and power it back on. If it stays on, check all speaker wires and speakers for shorts. If it cuts out, it needs service. If you need detailed troubleshooting help on this after testing receiver without speakers connected and it passes, post a comment and I can walk you thru it. Hope this helps.

Protet mode is a special diagnostic mode that starts when a fault is detected.

When in protection mode the unit is prevented from starting by protection circuit, so to prevent further damage.

Check the speakers and speakers wiring, a contact in speaker wires, or faulty speakers can send the unit in protection.

Try unplugging power cable for one hour or so. then connect cable back and see if you get rid of protect state. Sometimes accumulation of electrostatic charges inside circuit capacitors can kick in protect mode. In that case unplugging the unit from main for some times can get rid of electrostatic charges, and reset circuits by draining power completely.
If that was the problem, you will not get Protect when plugging back power cable.

If you do all the above and still get Protect, then there is a real fault.

In that case the unit may be disassembled and tested to find the fault.

If that is the case I suggest contacting the manufacturer at the number listed on the owners manual, or asking a quote on repair to a local technician.

The input filter capacitor of ur sub may be damaged,the possibility is upto 99%.u can identify the capacitor easily as it will be the the larger capacitor in that board and is located near the power supply entrance.the component costs within a dollar