Sony HCD-DZ880W Receiver Dosen't Power ON

[ortiko]

I have this sony receiver and it doesn't power on at all...

Power Supply model: 09DAV-POWER-MR-MP-13
I started looking the power supply and fuse on it are ok.
At rectifier output i measure 32V dc

The red circle the output is 8V and on pcb it reads 32-0 32-0
So i suppose this is the problem but don't know how to find the defective part
Every part on pcb looks ok...

Any suggestions will be appreciated

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

I have the PS circuit below.

Will take some measurements later today and come back

If someone can help will be appreciated

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

Have changed the capacitors with new ones and problem remains
Strange thing is that volts at emitter of q901 is 1,6V
Before i replace the caps it was 15,8 V

Is the transistor defective? (Q901)
Any idea what to check ?

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

Can you give me the link to this service manual so I can look at them in details? or upload it.
I would recheck your works and the polarity of the new cap you installed.
BTW, you should probably remove this thread to audio section.

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

I uploaded the Service Manual

I have double checked the capacitors polarity and value that have been replaced. They are ok.

Don't know how to remove the thread...If possible a moderator can help.

Thanks for helping

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

So which caps did you replace?
I will download the SCH and see what is going on.

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

OK:
"At rectifier output i measure 32V dc" which rectifier are you looking at?
Have everything hooked back up and report the reading on each pins (except GND pins) of the connectors CN904, CN906, CN908 when the power switch is activated and when the power switch is activated. Use chassis GND (we are working in the secondary side) as the GND ref. point for your meter.

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

OK:
"At rectifier output i measure 32V dc" which rectifier are you looking at?
Have everything hooked back up and report the reading on each pins (except GND pins) of the connectors CN904, CN906, CN908 when the power switch is activated and when the power switch is activated. Use chassis GND (we are working in the secondary side) as the GND ref. point for your meter.

"At rectifier output i measure 32V dc" which rectifier are you looking at?
Sorry. I meant 320 Volts

I hooked back everything and ther is no voltage at all pins !!! CN904, CN906, CN908 with switch on and off no voltage at any pin

After that i replaced the three capacitors c912,c926,c908 AGAIN with new ones to be 100% sure and no voltage at any pin again...

The only difference i have detected is at emitter of Q901 with switch on it is 1,6V and with switch off it is 0v
It seems like a part for protection has failed

Any idea where to start for finding the problem ?

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

OK, let me look at the power supply SCH in details and I will give you the test points to check.

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

I really appreciate your help.
Thank you !

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

OK, Do not activate the power switch yet, please report the DC Voltage reading on the CN906 PIN 4, 5, 6, the Emitter Voltage of Q922, the resistance reading of 10 Ohms resistor R905.

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

With not activated the prower switch at CN 906 pins 4,5,6 dv volt is 0.
The emitter Voltage of Q922 is 80 mV
Resistance reading of R905 is 17 Ohms (it is on pcb and value changes constantly to 30,25,40...most of the time it is 17 Ohms)

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

Those Voltage on CN906 Pin 4, 5, 6 are the always on and should be present when the unit is plugged into the outlet.
Right now the IC921 for the always on power supply is not functioning so there is no DC voltage from Q922 to feed Q901 to run the 31.5V switched power supply (IC901) for supplying the Voltage for the power amplifier sections, this power supply is turned on by the command signal from main board that fed into pin 2 (EN) of CN906.\
So right now we need to get the IC921 circuit working again.
You need to check the fusible resistor FR929 which supplies the Voltage to run IC921. There are two start up caps C912, C926 that you need to check the dc Voltage RIGHT AT THE TWO LEGS OF THE CAPS, BE REAL CAREFUL SINCE YOU ARE WORKING IN THE PRIMARY SIDE OF THE CIRCUIT, you can work on the board by itself without having any other boards connected to it, just the power supply cord., We need to get the voltage on pin 4, 5, and 6 back first.
BTW, I cannot find the spec sheet for the IC921 MR4020-7103 yet.

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

Have some news to report!

I cheaked the fusible resistor FR929 Volts at one side 320V and other side is 0V.
So i removed the FR929 and checked it with ohm meter and it reads no continuity..(open circuit)

Question is can i replace this with 1 ohm 1 watt resistor that i can find easy or must use the exact part that is removed (see photo of FR929)?

There are two start up caps C912, C926 that you need to check the dc Voltage RIGHT AT THE TWO LEGS OF THE CAPS, BE REAL CAREFUL SINCE YOU ARE WORKING IN THE PRIMARY SIDE OF THE CIRCUIT

Before taking apart the FR929:

C912---> 0 Volts
C926---> 3,9V

I hope that i will find the IC921 MR4020-7103 datasheet today

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

Found the Datasheet of IC921 MR4020-7103 !

https://cdn.badcaps-static.com/pdfs/...2e49b3d1b6.pdf

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

OK, you need to check the resistance on that end of the resistor which does not show the voltage and the negative legs of the main filter cap to find out if the Power IC is shorted out or not, it may have been the reason the fusible resistor blown open.

[Agent24]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

Question is can i replace this with 1 ohm 1 watt resistor that i can find easy or must use the exact part that is removed (see photo of FR929)?

You can use a normal resistor for testing purposes, but after repair you must use the correct fusible resistor for safety, to prevent fire.

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

OK, you need to check the resistance on that end of the resistor which does not show the voltage and the negative legs of the main filter cap to find out if the Power IC is shorted out or not, it may have been the reason the fusible resistor blown open.

Just to be 100% sure i have in below photo my resistance readings:
(The measurement was taken with power supply not plugged to mains power)

[budm]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

OK, that is fine, I was looking for <10 Ohms if it is bad.
At this point the static resistance is good but it does not mean that the active resistance (devices are turned on) is good. You can use 1~1.5A fuse in place of the resistor for testing.

[ortiko]

Re: Sony HCD-DZ880W Receiver Dosen't Power ON

Well i am back with not so good news
I powerd on the PS with 1,2 A fuse in place of FR929 as budm told and fuse blown and burned smell came from IC921 MR4020-7103

After that i replaced fuse (FR929) and without mains power connected i tested the resistance of IC921 and it is 28 ohms...

So this IC is dead i suppose and hard to find for replacment ?

In a store i looked i found only the one in first picture below(the burned out is second pic with long legs)

Will this work for replacement if i use wires to connect all legs as the old one ?