Sony Dav-dz350 no power on secondary

[sarry86]

Hi guys, I have this power supply which has a problem providing power on the secondary portion, seems like there's no power past the transformers, I checked the PFF4N80 which had shorted and replaced it with a new one, I then checked the optocoupler part and found that the TL341 IC too had shorted out so I replaced it with a new one as well, I measured everything on the secondary side of my power supply and I found a 1N5819 diode shorted, I replaced it with a new one, nothing else seem to have a problem, I am out of ideas, please anyone help me out what should I look after

[R_J]

Re: Sony Dav-dz350 no power on secondary

If the PFF4N80 was shorted, check the 1Ω resistors and replace the ssc6200, check the 1N4148, 10Ω and 47Ω. also replace the 47µf/50v

[sarry86]

Re: Sony Dav-dz350 no power on secondary

If the PFF4N80 was shorted, check the 1Ω resistors and replace the ssc6200, check the 1N4148, 10Ω and 47Ω. also replace the 47µf/50v

Thank R_J for the reply, I have already changed PFF4N80, ssc6200 amd and all the 1 ohms resistors, I am going to check the rest you mentioned once I get back home then I will get back to you

[sarry86]

Re: Sony Dav-dz350 no power on secondary

I checked those and I found 1N4148, 10Ω and 47Ω not functioning at all so I replaced them, Also I had already replaced the ssc6200 because when PFF4N80 shorted, it blew up together with all the 1Ω resistors and the ssc6200, Now that all the components above have been replaced, still there is no output power, but sometimes I get some 12> voltages if I put my -ve multimeter probe on the -ve of the bridge rectifier and measure my output, is there anything else I can check?

[R_J]

Re: Sony Dav-dz350 no power on secondary

You can NOT use the (-) of the bridge rectifier to check the voltage on the secondary side. The primary and the secondary are isolated from each other.
Can you list the board reference numbers you replaced, If ic904 was bad, I suspect IC901 is also bad as well as zd902and maybe R938 is open.
What is the vcc voltage you get on the ssc6200? R937 may be open

[sarry86]

Re: Sony Dav-dz350 no power on secondary

I replaced all R930 and R931 resistors (1R0), D903, R919, R933, IC903, IC938 and IC901. I get 2.15 volts on IC903 VCC

[sarry86]

Re: Sony Dav-dz350 no power on secondary

Actually it's -2.15 volts on its vcc

[sarry86]

Re: Sony Dav-dz350 no power on secondary

I replaced all R930 and R931 resistors (1R0), D903, R919, R933, IC903, IC938 and IC901. I get 2.15 volts on IC903 VCC

You can NOT use the (-) of the bridge rectifier to check the voltage on the secondary side. The primary and the secondary are isolated from each other.
Can you list the board reference numbers you replaced, If ic904 was bad, I suspect IC901 is also bad as well as zd902and maybe R938 is open.
What is the vcc voltage you get on the ssc6200? R937 may be open

Can you help me get through this?

[R_J]

Re: Sony Dav-dz350 no power on secondary

What point are you using for your meter ground when checking the voltages in the primary?

What part did you use for Q901? Was the case the same as the original? or did it have an isolated case. I checked other pictures and Q901 is an isolated case. (like Q902)

[sarry86]

Re: Sony Dav-dz350 no power on secondary

Negative tip on IC903 leg 8 and positive one on leg 2. I replaced Q901 with the one on the uploaded image but i only have thermal paste applied between the Q901 and heatsink so that they won't touch each other

[R_J]

Re: Sony Dav-dz350 no power on secondary

Thermal paste is not an insulator! You need the correct case mosfet. besides the screw is shorting out the mosfet as well. An insulator kit might work but it is best to use the correct part. PFF4N80 not SSP4N80
You must have something in backwards to be getting negative voltage on the vcc pin. Are you sure you installed ic903 the correct way?

[sarry86]

Re: Sony Dav-dz350 no power on secondary

You must have something in backwards to be getting negative voltage on the vcc pin. Are you sure you installed ic903 the correct way?

Oh no! I had an IC903 installed all wrong, I was in the middle of soldering a new one the correct way but we have a problem with electricity atm, I will be right back later on

[sarry86]

Re: Sony Dav-dz350 no power on secondary

Sorry for the late feedback, i re soldered the IC903 now it doesn't read negative voltage, vcc and ground i get 2.12 volts, but if i measure those two filter caps (CE901 and CE902) I get 112 volts, that isn't okay is it? ��

[R_J]

Re: Sony Dav-dz350 no power on secondary

How are you measuring the capacitors? You don't seem to understand the schematic. CE901 and CE902 are in series. You need to check the voltage between CE901 negative terminal and CE902 positive terminal, but that will only give you the raw dc voltage which should be close to 330vdc.
Check the voltage on ic903 pin 4 being careful not to short any pins and blow it up.
Check R935, it should be 100K, you may need to remove one end to get a proper reading

[sarry86]

Re: Sony Dav-dz350 no power on secondary

I get 250vdc measuring them filter caps in series, I suspect these caps are not filtering at all, IC903 pin 4 now has 2.4 volts, I removed R935 and it indeed has 100kΩ

[R_J]

Re: Sony Dav-dz350 no power on secondary

I doubt the main filters are that bad. The voltage on ic903 pin 4 is way too low, it should be around 15~20 vdc, Something must be loading it down, likely something on the vcc line

Also check the A/C voltage at the ac input (CN901) Then check the A/C voltage across 2 & 3 of the bridge rectifier.

[sarry86]

Re: Sony Dav-dz350 no power on secondary

I compared the IC903 I replaced with the new one, they are the same but I am not totally sure, are the SSC6200 and SSC620S really the same? I am a noob at comparing these

[R_J]

Re: Sony Dav-dz350 no power on secondary

I believe they are the same. The SSC620s could be a newer version. The complete datasheets are hard to find.

[sarry86]

Re: Sony Dav-dz350 no power on secondary

I get 210VAC on both CN901 and across 2 & 3 bridge rectifier, the R937 3R3 resistor measures 4.0ohms

[R_J]

Re: Sony Dav-dz350 no power on secondary

Your A/C voltage is a bit low so the DC voltage across the main filters will also be low, This should not effect the standby circuit from working. The circuit is very simple with only a few components, it should not be that hard to locate what is causing the start voltage to be reduced to 2.4v