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SONY Treble button issue

Rick79

Nov 26, 2014
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I have a SONY STR-K740P
When I push the "Treble +" button, it acts as if I'm pressing the sleep timer button. Would a bad resistor or capacitor cause this?
 

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kellys_eye

Jun 25, 2010
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Would a bad resistor or capacitor cause this?
Anyone's guess.

If it is genuinely creating a 'sleep function' action then you need to follow the button tracks until you get the area where the keyboard (button) matrix is being read by the processor and determine if there is a fault on the control lines.

Check the operation of ALL buttons. If one of the keyboard matrix lines is faulty it will likely create other issues on the other buttons that are part of that matrix line.
 

73's de Edd

Aug 21, 2015
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Sir Rick79 . . . . .

All its mass inter page complexity, is now simplified down to a one page UNITIZED draw out .
Initially take note of the left IC1601 System Control and its pins 38----41 as being its Analog to Digital conversion inputs and each is receiving a voltage reference from the R1627---30 from a common B+ supply buss and a bit of capacitive decoupling to ground..
Then you follow the YELLOW BRICK ROAD path to the right, where it then travels to the keyboard and break out again as AD1-AD2-AD3 and AD4 and serving 4 cluster strings of keyboard switches.

Refer to your AD1 line which relates to your TREBLE + function and you see that pressing that button will cause a voltage shift at the u/p, and that voltage is detected and converted to a digital value of serial 1 & 0's and that then feeds to the dedicated chips that do your digital tuning audio switching and audio control functions.

You can see that the MUTING button shorts that voltage reference voltage resistor to ground for 0V.
The next INPUT MODE button shorts a 470 ohm resistor to ground to make a 10K /470 ohm voltage divider for that produced reference voltage into the AD1 converter internally.
Your TREBLE + then shorts a series 470 and 1K ohm resistor pair to ground.
Then each switch, to the right, progressively going on down the, line causes less of a voltage shift for its produced voltage reference for their distinct functions.
The 22K and 47 K's down on the end have lesser effect on the voltage reference . . . HOWEVER . . . they have all been selected values to produce distinct voltage stair steps.
You need to be concerned on checking the circuitry associated with the AD1 buss, and the first three switches and R112 and R111 associated with them would be most suspect.
That's potentially only 10 interrelated functions.
I could not relate a pushbutton function, as being a snooze function . . .fill me in on its labeling.

RELEVANT UNITIZED SCHEMATIC SNIPPET . . . .

6uJtNLI.jpg


73's de Edd
.....
 

shrtrnd

Jan 15, 2010
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There's not much to add to 73's de Edd's post. But I'll add my two-cents worth.
My experience is it's almost always the switches themselves.
I live in the desert and use an evaporative cooler. When I flip that sucker on, my TV, stereo, and other assorted entertainment devices intermittently go ape, because condensation from the evap makes switch contacts through the water that shouldn't be there. My symptom sounds a lot like your symptoms.
Maybe the switch is dirty from finger oils or something else, allowing malfunction.
If the switch is good, it might need to be cleaned.
... so ends my two-cents worth.
 

Rick79

Nov 26, 2014
283
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Nov 26, 2014
Messages
283
Sir Rick79 . . . . .

All its mass inter page complexity, is now simplified down to a one page UNITIZED draw out .
Initially take note of the left IC1601 System Control and its pins 38----41 as being its Analog to Digital conversion inputs and each is receiving a voltage reference from the R1627---30 from a common B+ supply buss and a bit of capacitive decoupling to ground..
Then you follow the YELLOW BRICK ROAD path to the right, where it then travels to the keyboard and break out again as AD1-AD2-AD3 and AD4 and serving 4 cluster strings of keyboard switches.

Refer to your AD1 line which relates to your TREBLE + function and you see that pressing that button will cause a voltage shift at the u/p, and that voltage is detected and converted to a digital value of serial 1 & 0's and that then feeds to the dedicated chips that do your digital tuning audio switching and audio control functions.

You can see that the MUTING button shorts that voltage reference voltage resistor to ground for 0V.
The next INPUT MODE button shorts a 470 ohm resistor to ground to make a 10K /470 ohm voltage divider for that produced reference voltage into the AD1 converter internally.
Your TREBLE + then shorts a series 470 and 1K ohm resistor pair to ground.
Then each switch, to the right, progressively going on down the, line causes less of a voltage shift for its produced voltage reference for their distinct functions.
The 22K and 47 K's down on the end have lesser effect on the voltage reference . . . HOWEVER . . . they have all been selected values to produce distinct voltage stair steps.
You need to be concerned on checking the circuitry associated with the AD1 buss, and the first three switches and R112 and R111 associated with them would be most suspect.
That's potentially only 10 interrelated functions.
I could not relate a pushbutton function, as being a snooze function . . .fill me in on its labeling.

RELEVANT UNITIZED SCHEMATIC SNIPPET . . . .

6uJtNLI.jpg


73's de Edd
.....

Thanks for the schematic. Its weird that the S113 says "multi channel in" on the schematic and on the circuit board, but on the face plate of the receiver, it says "sleep" and functions as a sleep timer. Im gonna check out S112 and see if its dirty.
 

Rick79

Nov 26, 2014
283
Joined
Nov 26, 2014
Messages
283
There's not much to add to 73's de Edd's post. But I'll add my two-cents worth.
My experience is it's almost always the switches themselves.
I live in the desert and use an evaporative cooler. When I flip that sucker on, my TV, stereo, and other assorted entertainment devices intermittently go ape, because condensation from the evap makes switch contacts through the water that shouldn't be there. My symptom sounds a lot like your symptoms.
Maybe the switch is dirty from finger oils or something else, allowing malfunction.
If the switch is good, it might need to be cleaned.
... so ends my two-cents worth.
Thank you! I didn't think about them being dirty. Plus It makes more sense to me now knowing how they function and seeing the schematic above.
 

shrtrnd

Jan 15, 2010
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Computer stores and electronic parts stores sell spray-can contact cleaner.
I'd give that a shot.
Hope you get lucky and it's only a switch problem, and not an actual circuit fault.
 

Rick79

Nov 26, 2014
283
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Nov 26, 2014
Messages
283
Computer stores and electronic parts stores sell spray-can contact cleaner.
I'd give that a shot.
Hope you get lucky and it's only a switch problem, and not an actual circuit fault.
Yeah you were right, it was just a bad switch. I tried cleaning it, but it didn't help. I just swapped it with the mute switch and it worked.
 
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