Sony STR-KM7 Not Powering On

[mojos911]

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.

[budm]

Re: Sony STR-KM7 Not Powering On

Can you please upload the service manual/schematic?

[R_J]

Re: Sony STR-KM7 Not Powering On

You should have standby voltage on CN271 pin 5, or across C904, Is it there?

[mojos911]

Re: Sony STR-KM7 Not Powering On

Here is the full schematic Budm.

[mojos911]

Re: Sony STR-KM7 Not Powering On

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

[Purge98]

Re: Sony STR-KM7 Not Powering On

Did you ever solve the problem?
I have exactly the same issue and would welcome any advice.
(I know this thread is old).

[Purge98]

Re: Sony STR-KM7 Not Powering On

You should have standby voltage on CN271 pin 5, or across C904, Is it there?

I have 13.2 v across C904
and 12.7 v at CL214 (pin 5 on CN271).

Any ideas?

[Purge98]

Re: Sony STR-KM7 Not Powering On

I have 13.2 v across C904
and 12.7 v at CL214 (pin 5 on CN271).

Any ideas?

UPDATE.................................

I shorted out the relay RY901 output terminals and it works.
There must be a problem with the signal to the base of transistor Q901 which drives the relay coil. I couldn't be bothered to find out what it was.

This solution may help mojos911