Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

[Quaddro]

Hello everyone.

i have psu with dead 5vsb voltage. Xigmatek tauro 400w, 5vsb use STR-A6069H.

First guess, dead IC. So i order new one and replace it.

But no success. Still no 5vsb output.

I've checked all diode, replace the small capacitor, test the resistor around the ic, but not found any error component.

Further inspection, i found vcc input of A6069H is bouncing between 8v to 13v. which is based on datasheet need typical 15.3v to start.

-

I guess, maybe unstable voltage of A6069H VCC, paralysed 5vsb.

What can cause the unstable vcc voltage ?

Because i already checked all components in primary side, can some faulty component in secondary make this problem?

Thanks alot.

[Per Hansson]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

A good start would be washing the board, the PCB looks awful on the component side and it could be simply a short circuit somewhere.

[Quaddro]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

A good start would be washing the board, the PCB looks awful on the component side and it could be simply a short circuit somewhere.

i was torture the board with solder and desolder trying to put off the component, measure it, and put it back. That's why it's looks like messy, due to flux that i use.


but yes, i've already wash with small brush and gasoline (on the component side) every time i try to turn it on.

[sam_sam_sam]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

Did you check the optic sensors to see if might your problem
Did you check for shorts on the fire volt supply rails

I circle an IC chip that looks like there might be a burn mark on it or is just the way the light is hitting it

One note cleaning a board with gasoline is very BAD idea use some type of flux remover it work very well and very easy to use or contact cleaner would be a second choice

[Quaddro]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

Did you check the optic sensors to see if might your problem
Did you check for shorts on the fire volt supply rails

I circle an IC chip that looks like there might be a burn mark on it or is just the way the light is hitting it

One note cleaning a board with gasoline is very BAD idea use some type of flux remover it work very well and very easy to use or contact cleaner would be a second choice

Measuring with dmm diode measurement, i've found that all the optocoupler is not faulty.
but, i'll change all the optocoupler with the working ones.

Gasoline is just quick solution, my flux remover is depleted.

The ic that you've circled is 5vsb pwm controller stra6069h. and that's not a burn mark. just like your guess, the way the light is hitting it .
i've change it with new one, and still no 5vsb.

i'll try to draw simple schematic, maybe it helps to enlighten me.

this is the new high resolution picture. idk, but i cant edit the main post.

[sam_sam_sam]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

What is the part number of the IC chip that is circulated

[Quaddro]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

what is the part number of the ic chip that is circulated

wt7525

[Stefan Payne]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

So the question is:
does the +5VSB Chip get input voltage or is there a short on the secondary side??
What's the +5VSB Transformer doing?

[momaka]

Re: Xigmatek Tauro 400w, no 5vsb, Unstable Vcc input

First check resistance of R2. When the original STR-A6069H blew, it is possible to have taken out that resistor. R2 should have a very low resistance (it's a current sense resistor after all).

Next, check the 5VSB output rectifying diode on the secondary side. Also replace the 5VSB output caps if you cannot check/measure their capacitance and ESR. Just because they look good doesn't mean anything. I'm learning more and more lately the hard way what happens when you ignore crap cap brands - seems like some of them start going bad without any visual signs.

If these items check out...
From the 5VSB transformer's primary side auxiliary winding, you have two rectified rails done by diodes D2 and D1. One of these should supply power to the STR-A6069H 5VSB PWM-FET chip. The other is probably for the primary-side PWM/PFC controller for the *main* power supply. Find out which diode (D1 or D2) supplies power to the main PS PWM/PFC chip and remove it from the board. Now try powering the 5VSB back up. Anything changed?

If not, replace TL431/KA431 shunt regulator on secondary side associated with the 5VSB feedback circuitry.