Sony HCD-DZ880W Receiver Dosen't Power ON

[Agent24]

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

No, they have just formed (bent) the legs differently to your one. You'd just need to take some pliers and form them to however you need them for your board.

Also before replacing it, you should probably check the snubber components (looks like C921 and D921 at least) as a failure in those could cause the IC to fail again.

[ortiko]

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

They are significantly shorter than the one is burned.
Will go tomorrow and buy it and add wires to some of the IC legs.
I hope there is no difference of the IC's specs

[Agent24]

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

Ah, yes that could be a problem. Soldering wires will probably work, but on something switching high currents at high frequency... it could be a bit.. ehh.

As long as they are straight, soldered well, it'll hopefully work. Would be best if you can source one with longer leads.

[ortiko]

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.

I am back with new IC MR4020 installed after long and hard soldering of the pins but it is ok and think it is working fine

Took some measurements of voltage at CN906 and CN908 (PS not in case and only cable to mains is connected)
At below photos i have the report of all Voltages

[Agent24]

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

So the 31.5v rail is low, but IC921 was blown, but it does not handle that rail. So maybe whatever is wrong with the other circuit blew IC921 as well?

[ortiko]

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

Maybe the IC was blown off because when i removed the ps from case to check it accidently touched the metal bottom of case and a "spark" occured

Like budm said

"So right now we need to get the IC921 circuit working again" I think this part is working now and
"Voltage on CN906 Pin 4, 5, 6 are the always on and should be present when the unit is plugged into the outlet"

So now i am starting from the beginning...
Help please

[budm]

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

"Maybe the IC was blown off because when i removed the ps from case to check it accidently touched the metal bottom of case and a "spark" occured" OK, that was the missing info I did not have as to why the always on power supply stops working when we working on the 30V power supply for the power amp section.
So yes, back to the original problem.
So what DC Voltage do you have at E, C, B of the Q901 which is switched ON (EN pins goes HI) to pass the 20VDC to supply the VCC to run IC901?
That EN pin control signal is from the main board should be ON steady. What you can do is to disconnect that wire feeding the EN pin first and then use 100~500 Ohms between the EN pin and the EN 4V to force on the 30V power supply.

[ortiko]

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

In picture one i have the DC Voltage E, C, B of the Q901
Must i connect 100~500 Ohms resistor as picture two ?

Will not do anything until you reply just to be sure

[budm]

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

OK, something does not make sense here, Q901 is not biased on due to the fact that the E-B junction voltage is the same, it should be ~0.6V difference between E and B.
Since Q901 is not biased on then I do not expect any out put Voltage on the Collector pin (transistor is used as a electronics switch to supply VCC to the SMPS IC when EN signal is present). So if you power up the board by itself without other board connected, there should be no voltage on the C of Q901 until force on is applied.
I would check the Q901 off the board, it may have leakage resistance between E and C.
The input Voltage to the E of Q901 is also low per SCH which should be 20V.
The force on resistor connection is correct.
BTW, do you have about 20V at the E of Q922?

[ortiko]

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

Voltage at E of Q922 is 11V (With only the cable to mains power pluged)

[ortiko]

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

I would check the Q901 off the board, it may have leakage resistance between E and C.

Have also replaced Q901 with new one and voltage at E, C, B is exact like before replacing it...

[ortiko]

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

Is it normal to have on pin7 of IC921 and GND 322V ?

In circuit diagram it says 152 on pin 7 and though maybe i must report this ?

[budm]

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

Correction, the IC 921 is working because you are getting the always output Voltages, There will be high frequency pulse at the Drain pin 7 of that IC which your meter cannot measure, I do not know how they come up WITH 152V when the feeding Voltage to the transformer is >300vdc.
BTW, did you find the spec sheet of the IC 901 STRF6138?

[Agent24]

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

Maybe they mean to measure with a RMS meter, if the 300VDC was being switched with 50% duty cycle wouldn't that show 150V RMS?

[budm]

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

The pulse on that Drain pin 8 will be in 70~100KHz range which is higher than most AC meter can read, and the kick back spike even with snubber R-C circuit (the snubber cap C921 is rated at 2KV for the D to ground through R922) cannot keep it below the supply voltage.
PIN 7 is the Vin (it is shown on the SCH as 152) which goes back to the output of the bridge D901 with the red label of 15.2! I think there are many typo on the SCH.
BTW, my post 33 should have said pin 8 for the Drain, pin 7 is the Vin from the main bridge rectifier.

[ortiko]

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

Could not find anything about the IC 901 STRF6138 yet.

[budm]

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

I see the pin out in the service manual but not the Voltage requirement to run, there is minimum voltage that the IC requires to run.

[budm]

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

Can you please take the resistance reading between the two legs of C908, no power applied to the unit.
https://www.badcaps.net/forum/attach...1&d=1415902213

[vinceroger69]

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

theres a post here but its in spanish showing that chip in use and some voltages maybe worth a read
http://www.dtforum.info/index.php?to...prev_next=prev

[ortiko]

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

Tthe resistance reading between the two legs of C908 starts with 39 Mohms and slowly it decreases...