Sony STR-K740P protect mode

[testas86]

Hi i have a sony STR-K740P that once i turn it on it goes in to protect mode. Ive done some research and sony says it could be caused by speakers being plugged in incorrectly. Ive removed the speakers completely and tried to turn it on with nothing plugged in just power and it still gives me the same message. is there anything i can look for on the logic boards?

[cadiman]

I have had these give me logic trouble not sure about yours. I would check output ics for shorts. If you run 4 ohm speakers on these outputs that is a slow death for them. I don`t know how old yours is, but they don`t make them the way they did years ago. If you are running normal 8 ohm loads and had trouble then also check solder joints and plug connections. Make sure output connections are free of loose/frayed wires (seen that alot).

If it is logic then most likley needs some board re soldering.
Good luck

[Toasty]

Outputs and/or drivers.

Photos of that area?

Service manual: http://elektrotanya.com/sony_str-k74.../download.html

[testas86]

this happens with nothing plugged in to the speakers area and it still does it. i have it taken apart and ill be uploading picks shortly

[testas86]

ok so while i was taking it apart i resoldered all the joints on the back of the logic board and put it all back together just to see if that would help and when i turned it on it worked but i also noticed that i didnt plug in the stk pwb 1-687-113-11 and when i plugged that back in i got the protect mode again. any ideas? also does anyone know what the stk pwb is or does

[Toasty]

Did you get the service manual? It will tell you in there.

Toast

[testas86]

so it turns out that the stk350-030's on the stk pwb are what went bad once they come in and i replace them it should be good as new

[Th3_uN1Qu3]

That's good. The STKs are the power amplifiers, and they generally don't like 4 ohm loads.