HELP replacement or equivalent of this diode T2D 83

[budm]

Re: HELP replacement or equivalent of this diode T2D 83

Well I was way off. You are right, resistor shows 197k ohms and D106a shows open.
I just assumed when I saw the burn marks.

For U101 looks like pin 7 Drain burned up. Is it possible it's just U101 that's bad?

Yes, it can be just blown SMPS IC.

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

I replaced U101, still no standby power. Any other ideas on what to check next?

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

If this helps?

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

Can someone help me with this one? Still no standby power after replacing U101 and all the main transistors. Can't find anything else obviously wrong, have the voltages shown above but no power on the cold side of the board.

[R_J]

Re: HELP replacement or equivalent of this diode T2D 83

The U1 ic internal startup cell should produce aprox. 8 volts on pin5. I suspect C104 is bad (as in open) or maybe D107 is shorted?

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

I replaced C104 but no difference. On U101, pin 8 has 20V. Pin 5 has 3.3V. D107 not shorted.

Tried replacing U101 again, no change.

BTW C104 in that schematic shows a 47 uF cap where it was 4.7 uF in the board. The schematic may not be exact for this model but should close.

[R_J]

Re: HELP replacement or equivalent of this diode T2D 83

If the schematic is not correct, what is the U1 part number? is it a FSQ510? If you look at the datasheet for the ic you will see that the ic charges C104, Once the ic fires the internal fet, there is a voltage generated in the transformer scondary and the voltage coming from pin2 of the transformer gets rectified by D107, and THIS voltage will be around 20v to sustain the ic.
I would check pin 3 to ground to make sure that c105,D107 and the optocoupler are not shorted

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

Yes it's the same. Pin 7 leg was burned up when I got it.

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

Is it possible some small unidentifiable U or Q SMD transistor is bad on the bottom of the board and I should just give up on it? I hate to but can't find anything and don't know enough to trace the whole circuit.

[R_J]

Re: HELP replacement or equivalent of this diode T2D 83

There are NO transistors or other ic's for the standby circuit. for example, Q101 is only need to provide VCC for other parts of the circuit AFTER the power supply is turned on, but is not required for standby.
The standby circuit is very simple.
Where did you get the FSQ510? they could be bad fakes.

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

One was Digikey, one came in the Shopjimmy repair kit.

Is there a way for me to troubleshoot upstream or downstream of this area to see where the problem may be?

[kevinm34232]

Re: HELP replacement or equivalent of this diode T2D 83

Update: ZD103 was bad in addition to U101 loading down VCC line. Thanks R_J for the help!