Unknown component in 19V power supply

[rddube]

Re: Unknown component in 19V power supply

Ok, so got the LD7537RGL in yesterday, changed it and still no go. Nothing on the output and the input pin has 12-15v oscillating.

Not sure what to check next.

[rddube]

Re: Unknown component in 19V power supply

Was able to identify a substitute for the LD5533 with a LD7537RGL - not exactly the same but close, so on their way. Will keep you posted. Tks!

[rddube]

Re: Unknown component in 19V power supply

Got a reply from China that the LD5533 is out of stock. Searched the web, Ebay, Aliexpress, Yoycart, etc. and can't find it for sale! Anyone have any idead what I could use as a substitute or do you have any other sources where I can maybe find it?

[rddube]

Re: Unknown component in 19V power supply

No it's giving absolutely nothing, completely dead on the output. I ordered the chip, coming from China so probably a month or 6 weeks should be here. I'll keep you posted. Thks!

[R_J]

Re: Unknown component in 19V power supply

There is no way to tell by checking with a meter, they are a very complex ic. Without being able to see the output, it is likely best just to replace it. If there is no voltage at all on the secondary side, I suspect there is no output from the ic to switch the mosfet, even if it was detecting a fault, there should be some voltage on the secondary side, even a few volts.

[rddube]

Re: Unknown component in 19V power supply

After removing LD5533, I get 44V on pin 5 VCC, and when I reinstall LD5533, VCC drops to 12V and is not stable jumps from 14V to 12V. I checked for shorts on the chip itself, non, checked the path of every other pin to see if anything might be shorted, nothing. So I think the LD5533 chip is bad. What do you think?

[rddube]

Re: Unknown component in 19V power supply

Ah ok, I looked at the datasheet but mostly for the pinout of the LD5533. Had not looked at the schematics further down. Will try and trace that and make it correspond to my device. Will report further. Tks!

[R_J]

Re: Unknown component in 19V power supply

Hello R_J,

Not sure what you mean by I have a schematic too? Do you mean the datasheet of the LD5533?

Yes, Have you looked at the datasheet ?

[rddube]

Re: Unknown component in 19V power supply

Hello R_J,

Not sure what you mean by I have a schematic too? Do you mean the datasheet of the LD5533?

[R_J]

Re: Unknown component in 19V power supply

Hi R_J,

VCC goes to 18V when powered on, and then falls to 12V. Resistors all seem fine at their given values. Do you have a schematic for this? Tks!

Yes I have a schematic, and so do you. Its not exact but looks very close

[rddube]

Re: Unknown component in 19V power supply

Hi R_J,

VCC goes to 18V when powered on, and then falls to 12V. Resistors all seem fine at their given values. Do you have a schematic for this? Tks!

[R_J]

Re: Unknown component in 19V power supply

So since I am getting 12v on the VCC pin 5 of the LD5533 and no output on the out pin 6 (0V), do you think that LD5533 could be the culprit?

I did check the output pin path of the LD5533, it goes to a 30 ohms resistor and then to a 100 ohm resistor to finally go the the Gate pin of a 2SK3569 mosfet, who's source goes to the power winding of that transformer.

What do you think?

You need a scope to see the output of the ic to see if the 130kHz signal is there to drive the mosfet gate.
The VCC needs to be above 16v as per the datasheet to turn ON then can not fall below 7.5v. Does the VCC pin get above 16v when power is supplied? if not the ic will not start, this could be due to a bad ic. There is an internal 31v zener built into the ic so it might be damaged, or check the resistor RX1 (1.8M) between the main bridge rectifier and the vcc pin, maybe it has gone high in value. (same as R5,R6 in schematic)

[rddube]

Re: Unknown component in 19V power supply

So since I am getting 12v on the VCC pin 5 of the LD5533 and no output on the out pin 6 (0V), do you think that LD5533 could be the culprit?

I did check the output pin path of the LD5533, it goes to a 30 ohms resistor and then to a 100 ohm resistor to finally go the the Gate pin of a 2SK3569 mosfet, who's source goes to the power winding of that transformer.

What do you think?

The 30 ohm resistor and 100 ohm resistor measure exactly what they should. Any thoughts anyone?

[rddube]

Re: Unknown component in 19V power supply

So since I am getting 12v on the VCC pin 5 of the LD5533 and no output on the out pin 6 (0V), do you think that LD5533 could be the culprit?

I did check the output pin path of the LD5533, it goes to a 30 ohms resistor and then to a 100 ohm resistor to finally go the the Gate pin of a 2SK3569 mosfet, who's source goes to the power winding of that transformer.

What do you think?

[lotas]

Re: Unknown component in 19V power supply

This tester only checks the power winding for an interturn short circuit!, on others, the winding will always show that the transformer is not working.
If the tester has green LEDs on the power winding, this means that the transformer is working, but if you close the secondary windings, the green LEDs will go out.

[rddube]

Re: Unknown component in 19V power supply

If you have the ESR meter from the same company then check it with that if you get “0” then you might be on something but it still might not be bad but maybe questionable

Hi Sam,

No I don't have an ESR meter from the same company. I do have an ESR meter however from another company - what should I check the power winding or the output?

[rddube]

Re: Unknown component in 19V power supply

Ok, so I checked the power winding with my blue ring tester and that measures good. I checked resistance of the power winding which is +- 1 ohm and the output winding is +- 1 ohm. The other winding which is I guess the feedback winding measures also +- 1 ohm, but shows short on the blue ring tester.

[sam_sam_sam]

Re: Unknown component in 19V power supply

If you have the ESR meter from the same company then check it with that if you get “0” then you might be on something but it still might not be bad but maybe questionable

[R_J]

Re: Unknown component in 19V power supply

I doubt the transformer is bad, Check the resistance of the windings, if they are not open I suspect the transformer is ok. Did you check the primary and feedback windings with your ringer?

[lotas]

Re: Unknown component in 19V power supply

You are not diagnosing correctly, you need to check not the output winding, but the power winding, where the output is from the mosfet.