VStanby (V SB) question ?

[Khron]

Re: VStanby (V SB) question ?

I rest my case

Although, aren't Fuhjyyu's known for also failing without visible signs?

[bianchi77]

Re: VStanby (V SB) question ?

PS: In the first post i see that the 5VSB rectifier diode MIGHT be shorted...

I have replaced 5VSB diode, now I got 5.02V on VSB..

[stj]

Re: VStanby (V SB) question ?

i think if it was shorted the caps would explode.

[budm]

Re: VStanby (V SB) question ?

Yes, that 0.1Vf reading is not right, I do not believe the Vf can be that low.
It is in BOTH directions so it is bad. Same readings off the board? But it is for sure the rectifier diode for the 5VSTBY?
So the bottom line right now is that the 5VSTBY is steady at 5V with and without the load?

[Khron]

Re: VStanby (V SB) question ?

PS: In the first post i see that the 5VSB rectifier diode MIGHT be shorted...

[budm]

Re: VStanby (V SB) question ?

ok, so do you reckon there's no problem with SG6105 PWM chip ?
This PSU is completely off, was on before, but suddenly off...
and I got only V Sb 5V on.....

Was on before what? Before you are working on it?
You indicated the 5VSTBY is less than 5V and the power supply cannot be turned ON, so how did you get it to turn on then?
Also now you indicate "This PSU is completely off," So now you have nothing period, no STBY, none?
Very confusing.

[bianchi77]

Re: VStanby (V SB) question ?

ok, so do you reckon there's no problem with SG6105 PWM chip ?
This PSU is completely off, was on before, but suddenly off...
and I got only V Sb 5V on.....

[budm]

Re: VStanby (V SB) question ?

does it mean that I should desolder all the electrolityc caps and check, or just replace 'em ?

You already have bad brands of caps being used so just replace them with the good and correct type of caps, it wastes a lots time unless you want to buy the test equipment and analyze each caps OFF the board.

[budm]

Re: VStanby (V SB) question ?

Will a bad caps make the PSU completely shut off ? from I can see there's no problem with the diodes, I have check one by one....

Bad cap will cause the power supply not to run properly: I.E. will not run, low Voltage, cycling on and off, etc.

[bianchi77]

Re: VStanby (V SB) question ?

Will a bad caps make the PSU completely shut off ? from I can see there's no problem with the diodes, I have check one by one....

[bianchi77]

Re: VStanby (V SB) question ?

does it mean that I should desolder all the electrolityc caps and check, or just replace 'em ?

[budm]

Re: VStanby (V SB) question ?

You have already found two bad caps with bulging top, you might as well replace the whole set of the caps since bad caps may not show any sign of bulging on top, otherwise you need to check the Capacitance and the ESR of the caps.

[bianchi77]

Re: VStanby (V SB) question ?

Capacitor photos

[bianchi77]

Re: VStanby (V SB) question ?

Let me take close up picture so you can see what exactly it is...

[bianchi77]

Re: VStanby (V SB) question ?

are you talking about these caps ?

[Khron]

Re: VStanby (V SB) question ?

Those two black caps near the top of the board, near the small transformer - are they Fuhjyyu? Either way, if the 5VSB is low, those would be my first suspects.

[bianchi77]

Re: VStanby (V SB) question ?

The case :
Ritmo LPF2SS

[bianchi77]

Re: VStanby (V SB) question ?

Photo of the PCB, I 've taken out the secondary rectifier...
PCB serial code :
LEC-011
REV:1.2

Any ideas for the schematic ?

[bianchi77]

Re: VStanby (V SB) question ?

I've replaced them, no avail, can it be the rectifying diodes ? it's SBL1040 and when I measured it on diode test I got 0.1V...and there's one FET on 3.3V rail...
any ideas or schematic for it ? or it's faulty SG6105 PWM buck controller ?
I've tested the opto as well, all good...25 ohm when LED is on..

[bianchi77]

Re: VStanby (V SB) question ?

I've found 2 bulge capacitors 2200uF/16V on the secondary side...could be this one is the major problem ?
I haven't checked which one is connected to 12V / 5V...
I'll replace it and see...