Author Topic: Sony J30 PSU repair (Read 1101 times)

john2021 · « **on:** April 21, 2024, 01:01:16 pm »

Hello everyone,

I am trying to repair an old Sony j30 PSU, which I have no information about or schematics.
I am not an expert in electronics, but I would appreciate some help.
I recapped the whole PSU and still no output, though I get about 15-24v on the power transistors on the primary side. The MC33262 controller gets about 15v.
I get no power on the secondary side.
By the shottcky diode, where I think I have a short, as I replaced the component that seemed to be a diode (white like those connected to the power transistors with no marking on it, or the board itself). but it didn't change anything.
Any idea how to proceed?

Thank you in advance for any help
Joe

wasedadoc · « **Reply #1 on:** April 21, 2024, 03:08:02 pm »

That is a switch mode power supply. The "power transistors" on the primary side are working from the rectified 120 Volt AC input stored on that big 150uF capacitor. Not something that I would advise someone "not an expert in electronics" to be be working on.

john2021 · « **Reply #2 on:** April 21, 2024, 04:17:14 pm »

I very much appreciate the response and the safety advice. I know enough, I think, to try and repair this board with some help.
As I said the primary side of the board is working as far as I can tell.
I get AC power on the transformer primary side, but not on the secondary. The transformer I refer to is the one, which connects the primary and secondary side of the board – flyback I think is the correct term. Is there a way to test whether the transformer is bad, or the problem is down the secondary side of the board?
Thank you

Harry_22 · « **Reply #3 on:** April 21, 2024, 05:23:58 pm »

Dear Joe,

No problem that you don't have circuit diagram. MC33262 is PFC controller. Just open datasheet and you will have information about first stage of
PS.
Could you measure votage on the biggest capacitor 150uF@400V. Should be around 380V.

Laval · « **Reply #4 on:** April 21, 2024, 06:28:35 pm »

It would probably be a good idea to test those power transistors as they do drive the transformer.

john2021 · « **Reply #5 on:** April 21, 2024, 06:51:56 pm »

Thank you for the reply.
The voltage was about 320 dcv.

However, when I tested the board again, it shorted the k3234 transistor and blew the fuse. I think of replacing the transistor with a k3568 transistor, is that ok?

Thanks again

Harry_22 · « **Reply #6 on:** April 21, 2024, 07:18:05 pm »

Quote from: john2021 on April 21, 2024, 06:51:56 pm

it shorted the k3234 transistor

Why did you decide that the transistor had shorted?
Is it Q1?
Did it fail on its own?

john2021 · « **Reply #7 on:** April 21, 2024, 07:28:39 pm »

Yes, it is Q1. I must have shorted something while measuring voltage.
Just my luck.

Harry_22 · « **Reply #8 on:** April 21, 2024, 08:51:41 pm »

Could you answer exactly the questions:
1. Is it Short Circuit between D and S of Q1?
2. Is it SC between D and G of Q1?
3. Check the parts marked in red

Harry_22 · « **Reply #9 on:** April 21, 2024, 09:29:09 pm »

Check one more resistor near PFC controller under FB.

Harry_22 · « **Reply #10 on:** April 22, 2024, 08:05:01 am »

Joe,
meanwhile give me a good quality photo of the back of PCB. It's better to use a camera stand. Pack it in Zip file.

john2021 · « **Reply #11 on:** April 22, 2024, 09:05:03 am »

I attach a photo I took of the back of the board with my phone.
If you need better photos let me know, I will try to use a magnifier microscope camera.

Q1 pulled out of the board
1. All shorted
2. All shorted
3. diode B3 - shorted
R6 47.5 K Ω
Resistor next to R6 47 Ω
FB Resistor at IC 0.5-1 Ω
D2 – OK

I need to source the damaged parts.
Do the rest of the readings look to be OK?

Can a ka6 or 5d diode replace the B3 diode?
And can 12n60f cs10n60f k3568 be a good replacement for Q1?

Thank you very much again

john2021 · « **Reply #12 on:** April 22, 2024, 09:06:19 am »

I attach another photo of the back.

Harry_22 · « **Reply #13 on:** April 22, 2024, 12:21:04 pm »

Please see my comments below:

1. All shorted
This is bad. Means MOSFET Q1.

2. All shorted
This is very bad. Means that high voltage passed to controller output stage.

3. diode B3 - shorted
Probably you mean SOT-323 diode marked [B3] (I can't see). Probably it is 1SS184 or Schottky MMBD717LT1G.

R6 47.5 K Ω
Current sense resistor should be ~0.3 Ω

Resistor next to R6 47 Ω
Is is Ok but little bit burned. High voltage passed through this resistor to controller.

FB Resistor at IC 0.5-1 Ω
This is short. Ok.

D2 – OK
This is Boost PFC diode.

Do the rest of the readings look to be OK?
Controller also should be changed. Also R6 and [B3] and Q1.
Please check resistor marked [331].

Can a ka6 or 5d diode replace the B3 diode?
And can 12n60f cs10n60f k3568 be a good replacement for Q1?
I will have a look.

How did you measure [B3] and R6? Did you unsolder them?

john2021 · « **Reply #14 on:** April 22, 2024, 05:04:28 pm »

R6 is a ceramic resistor marked 0.22

I measured R6 and the diode marked as B3 on the board itself.

Diode mode on the diode beeps resistance mode on R6.

I measured again with a different meter and I got good news R6 is about 0.5.

Where is resistor 331 located?

Is there a way to test the controller?

Harry_22 · « **Reply #15 on:** April 22, 2024, 05:42:00 pm »

Please unsolder B3 and check it. Also check R6 at PCB.
331 is near the controller.
You can supply the controller with 15 volt (pin8) and look for signal at pin 7 (Gate).

Harry_22 · « **Reply #16 on:** April 22, 2024, 07:41:45 pm »

Here is PCB views for Paint.net
https://drive.google.com/file/d/1o8F8PD_h3s2HAJLKBaQ9ABi1_6qN4PEE/view?usp=sharing

john2021 · « **Reply #17 on:** April 23, 2024, 08:14:35 am »

I de-soldered B3 and tested it seems OK.

The board traces at B3 seems to be shorted so maybe that is the design, I don’t understand that.

There is a short in diode mode Anode to cathode and the between cathodes.

Then I took out Q1 and measured again.
Resistor 331 measured 331 Ω
R6 measured 0.5 Ω
Resistor next to R6 47 Ω
FB Resistor at IC 0.5-1 Ω

Harry_22 · « **Reply #18 on:** April 23, 2024, 09:17:35 am »

[B3] and R6 are in parallel (pls see the picture).

So you have to change Q1 and may be controller MC33262.
You can use MOSFET K3568 or CS10N60F as analog of K3234. Of course you may to solder Q1 change fuse and switch PS on. But it is bad way.

Check the controller fist then connect external DC power supply as mains. Most PFC work from 60 VDC. This is safe way.

john2021 · « **Reply #19 on:** April 23, 2024, 12:10:05 pm »

Replaced Q1 and now I get 313v on the biggest capacitor.

I get 12v on Vcc of the ic controller.

I took out the rectifier schotcky diode on the secondary side.

What should I check next?

Harry_22 · « **Reply #20 on:** April 23, 2024, 02:14:07 pm »

If your mains 110VAC this is perfect!

Schottky [B3] is required to cut a back spark on R6 parasitic inductance. Put it back. Just measure it in diode mode. It should be 0.25V in forward direction and "OL" back (means overload).

Please provide me the name of the second controller.

john2021 · « **Reply #21 on:** April 23, 2024, 03:50:13 pm »

The second controller markings are hard to read, but I believe it is ST L6574D.

The last measurements were with B3 installed.

I said I had took out the rectifier schotcky diode TRANSISTOR FCH30A04 on the secondary side, so there will be no load there.

Harry_22 · « **Reply #22 on:** April 23, 2024, 04:58:19 pm »

Please check following parts and measure the voltage.
What is the left one?
PS
For what reason did you remove this rectifier diode?

john2021 · « **Reply #23 on:** April 23, 2024, 06:05:50 pm »

Q7 - G TO D 311V G TO S 0V
Q8 – G TO D 1.8V G TO S 1.5V
G TO V_C53 1V
I know this is not good it was higher voltage before.
The initial problem was there was no power at the schotcky diode TRANSISTOR FCH30A04.
In diode mode it was shorted in all direction and to a white diode connected to the left anode that was also shorted.
So I also removed the diode (that looks like the one connected to Q7 Q8 collector).
Now when removed it reads open. I don’t know what kind of diode this is.
The other transistor is a regulator PQ1CG21H – no power

Harry_22 · « **Reply #24 on:** April 23, 2024, 07:57:24 pm »

Dear John, please check Q7 and Q8 by diode tester. Don't switch PS power on.
See to face of MOSFET. Plus (red probe) to right leg minus to central. Should be around 600mV. Then change + and -. Should be OL. And also OL between left leg and any other.

Where was higher voltage before? Please explain.

The "white diode". Do you mean a part that was in green oval (pls see the picture)?

Apparently the problem was in Schottky barrier diode FCH30A04. Is it has zero voltage between any leg? Please check again by tester in diode mode.
Do you have any to replace it (40V @ 30A)?


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Author Topic: Sony J30 PSU repair (Read 1101 times)

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