Turn on after 3 seconds turn off

[donskister]

I went to my friend he ask for my help if i can repair his kenwood model  RX-39 audio system. I turn on the power then it seems the unit have no problem but after 3 seconds the unit turn off and the message appear on the display ( Protect )..I noticed after repeatedly turn on i hear a clicking sound inside the unit before the unit turn off..I plan to open it by next week so that i can first gather informations before i try to repair it.

By the way... My friend told  me that sometimes he can used the unit for a couple of months when he will not used the unit for a weeks then after the unit will fail again then he will  not used the unit  for a weeks.....  it seems that the unit is working if  had taken a rest

 

[AN920]

Protection is activated when the sense circuitry determine a dangerous DC offset that may damage the speaker. The sense circuitry itself could be faulty and activate the protection relay. If you have a diagram you can make measurements to see what is going on.

 

[donskister]

AN920

im

 

[AN920]

The protection can activate with or without speakers connected. I this case my money will be on the protection circuit doing strange things.

 

[ante1]

Also check the output stages power transistors or power module whichever used in this unit and the large rear end caps.
If the fault is intermittent try freeze spray to locate the problem.

 

[donskister]

Hi Guys…

I just came to my friend place yesterday to repair his audio system with full of knowledge thru the