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Old 10-01-2019, 10:36 PM   #1
mojos911
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Default Sony STR-KM7 Not Powering On

So I have a Sony STR-KM7 with mains power - confirmed 240v - has no standby.
The relay RY901 - standby relay for allowing 240v to main transformer is not switching. No clicking sounds at all when mains power is supplied. No display and no illumination of any LED lights - nothing completely dead.
I have tested mains power circuit at mains connector on power avideo board - which is where the mains power comes into this unit and this tests good.

Tested Secondary side of T902 Power Transformer (sub) across terminals - 10.5v

Tested each secondary winding to ground is 5.25v.
Tested D904 on diode mode with DMM - .566v
Tested out of circuit - Q902 - B to E .725v - B to C .725v
Tested out of circuit - Q901 - B to E .725v - B to C .725v
Tested RY901 DC coil - 5v - with external power supply - working.

Now I am completely out of my depth as I cant seem to move forward from here as I believe all these tests are ok. Does anyone know of the operating startup proceedure that can help or even where I should check next.

I have attached a photo of the power avideo board and the schematic I am usng for reference.
Attached Images
File Type: jpg IMG20191002131921.jpg (1.38 MB, 7 views)
File Type: jpg IMG20191002131900.jpg (722.2 KB, 6 views)
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Old 10-02-2019, 02:17 PM   #2
budm
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Default Re: Sony STR-KM7 Not Powering On

Can you please upload the service manual/schematic?
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Old 10-02-2019, 02:34 PM   #3
R_J
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Default Re: Sony STR-KM7 Not Powering On

You should have standby voltage on CN271 pin 5, or across C904, Is it there?
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Old 10-06-2019, 06:13 AM   #4
mojos911
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Default Re: Sony STR-KM7 Not Powering On

Here is the full schematic Budm.
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File Type: pdf sony_str-km5_str-km7.pdf (5.91 MB, 1 views)
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Old 10-06-2019, 06:14 AM   #5
mojos911
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Default Re: Sony STR-KM7 Not Powering On

I will check those R J and get back to you.
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