VStanby (V SB) question ?

[bianchi77]

Re: VStanby (V SB) question ?

so the most possible faulty part is SBL2040 or SG6105, but I'm not sure for this PWM controller ...could be still good only shutting down the PSU because of no voltage from SBL2040..

[bianchi77]

Re: VStanby (V SB) question ?

what I've done with FET CEP603...
I connect DMM on diode test...black lead to S and Red to D....it's OL...
then I touch red probe to G to make it ON and I got 0.247V....is it good enough....
then I touch black probe to G to make it OFF and I got OL again...

I reckon this FET is ok....any opinions ?

[bianchi77]

Re: VStanby (V SB) question ?

is there any quick way testing FET with DMM ? I see the D S diode connection 0.546V looks like this FET is ok...

[bianchi77]

Re: VStanby (V SB) question ?

test with SBL2040...correction from SBL1040...
and some capacitor photos I've replaced...

[bianchi77]

Re: VStanby (V SB) question ?

here's the photo :

[bianchi77]

Re: VStanby (V SB) question ?

correction, I got 0.447V on Vf diode test for brand new FR302...

[budm]

Re: VStanby (V SB) question ?

If you look at how the Common Cathode SBL1040 is connected to produce 5V, it is connected in parallel, so it is still can handle 20A (if both internal diode Vf are matched and has proper heat management), but not at 35A

[bianchi77]

Re: VStanby (V SB) question ?

I'll show you the photo when I test it later on....for information sharing..

[bianchi77]

Re: VStanby (V SB) question ?

is it possible that my DMM battery low ?sometimes it can not start quickly....the voltage on DMM supply is 2 pcs AA batteries, which is 3V...

[bianchi77]

Re: VStanby (V SB) question ?

this power supply is writing a wrong spec...it's written 5V 35A on its lid....but the real ability is 5V 10A.....what a marketing strategy to take a lot of profit from constumer....10A and 35A diode is different...like you said between 3A and 10A just now...

[Khron]

Re: VStanby (V SB) question ?

That sounds really low, even if it was a Schottky.

When's the last time you looked into a diode datasheet?

https://cdn.badcaps-static.com/pdfs/...d12d739f56.pdf

Page 2, bottom left. Depending on the current passing through the diode (vertical axis), the forward voltage drop will vary.

That being said, we can't know how (in)accurate your DMM is, though...

https://cdn.badcaps-static.com/pdfs/...3aa0426335.pdf - A healthy FR302 should be showing at least 0.5-0.6v at the really low test-current a DMM uses.

[bianchi77]

Re: VStanby (V SB) question ?

I'm going to use it for a testing only...
I check from my DMM FR302 brand new, it's 0.17V....is it right ?

[Khron]

Re: VStanby (V SB) question ?

What exactly are you hoping to use this power supply for?

SBL1040 = 10A 40V
FR302 = 3A 100V

2x 3A = 6A, which is considerably lower than 10A, wouldn't you say?

Also, keep in mind that (ultra)fast rectifiers will have about 1-1.1v drop at rated current, as opposed to 0.6v or so, in the case of Schottky rectifiers (hint-SBL1040-hint).

[bianchi77]

Re: VStanby (V SB) question ?

They do it with 12V rectifier, 2 FR302 diodes are joined together to rectify...

[bianchi77]

Re: VStanby (V SB) question ?

Ok, the step I'll change the major caps first then replace SBL1040....the issue is, I need to wait for SBL1040 coming.....will be long 1 month or so....or can it be replaced with a pair of FR302 join together ?

[Khron]

Re: VStanby (V SB) question ?

so it can't be seen bulge if it's failed ....only measuring ESR and capacity off board for testing them ?

hmm....I'll replace them then...thanks there are 4 of them I haven't replaced...

https://www.badcaps.net/forum/showthread.php?t=388

It's easier to explain to you guys, if there's a schematic available, but I can't find it, anyone knows ?

Nope, you won't find (exact) schematics anywhere. On the bright side though, especially these cheapo PSU's all follow the same basic structure.
https://www.badcaps.net/forum/showthread.php?t=1238

another think in my mind, for example SBL1040 for 5V main is faulty....SG6105 will detect it and it will lock down the circuit, do you reckon ?

Yes, most likely the chip senses the under-voltage on the 5V line, and turns itself off (or at least the PWM side).

[bianchi77]

Re: VStanby (V SB) question ?

another think in my mind, for example SBL1040 for 5V main is faulty....SG6105 will detect it and it will lock down the circuit, do you reckon ?

[bianchi77]

Re: VStanby (V SB) question ?

It's easier to explain to you guys, if there's a schematic available, but I can't find it, anyone knows ?

[bianchi77]

Re: VStanby (V SB) question ?

I rest my case

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

so it can't be seen bulge if it's failed ....only measuring ESR and capacity off board for testing them ?

hmm....I'll replace them then...thanks there are 4 of them I haven't replaced...

[bianchi77]

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?

0.1Vf for another diode beside 5VSTBY, I have replaced 5VSTBY....and it's stable on 5.02V now.

There is another one, it's 5V main power supply rectifier SBL1040 (3pins)
on 12V rectifier it's 0.467V Vf.....but on 3.3V I can see it's using FET CET603...
Is there any possibiity that my PWM is faulty already ? it's SG6105

Because it has 3 functions : Power Supply Supervisor + Regulator + PWM
and it's not responding anymore to PSON anymore..
anyway to test this SG6105 ?