power good 0v

[placidocd]

Hello I'm newbie here and sorry for my bad English.
I have a problem with some ATX PSU. All voltage are normal, only grey wire (power_good) detect 0v. From where do I start for repair it?

[kc8adu]

Re: repair and troubleshoot atx power supply 435 W

moved to a new thread.
as usual we need brand,model,and good pics.

[Escort Eagle]

Re: power good 0v

How many ICs in controller Section ? And what is the number of that IC's ?

[placidocd]

Re: power good 0v

Thx, sorry for my retard post.
There are 3 PSU which same trouble with 0v 'Power Good'

1. FSP SAGA II 400



5v normal voltage


12v normal voltage


Power Good (grey) abnormal voltage


Inside


Weltrend WT7527


Test by shorten green and black wire, 0v Power Good also happen when plugged in to mainboard.

[domas]

Re: power good 0v

what about +3,3V, did you forget to test it?

also please check voltage on weltend pins 1 and 16
and 9th pin on weltrened, should be less than 1.2

take some time to analyze the internal circuit of the chip to see what can cause PGO (pin 16) to be low

[Escort Eagle]

Re: power good 0v

Change This 320μF/400V Primary Capacitor (Shown in the Image) with a new one . Your Power supply will be OK .

[cheapie]

Re: power good 0v

Change This 320μF/400V Primary Capacitor (Shown in the Image) with a new one . Your Power supply will be OK .

What makes you think that's the problem? It's running, so most likely that cap is good (or good enough, at least). I think the problem is on the secondary side.

[Escort Eagle]

Re: power good 0v

What makes you think that's the problem? It's running, so most likely that cap is good (or good enough, at least). I think the problem is on the secondary side.

Boss, I do not know - why have I told that . He wanted a solution . Just I have tried to give him a solution of his problem .

[senz_90]

Re: power good 0v

what about +3,3V, did you forget to test it?

also please check voltage on weltend pins 1 and 16
and 9th pin on weltrened, should be less than 1.2

take some time to analyze the internal circuit of the chip to see what can cause PGO (pin 16) to be low

how to check voltage on ic pins, is this means we check when connecting to the mains? is that possible with analog VOM at off conditions, i guess it is possible with DMM? i have same symptom with my PSU, it has a 2005Z IC
i didn't get a "power good" signal on gray colour rail. sorry for hijacking this thread just because have a same symptom.

[placidocd]

Re: power good 0v

Change This 320μF/400V Primary Capacitor (Shown in the Image) with a new one . Your Power supply will be OK .

I've read that in "Jestine Yong's handbook" and I replaced the cap with other, same capasity and bigger capasity I tried, but the problem not fixed.

What makes you think that's the problem? It's running, so most likely that cap is good (or good enough, at least). I think the problem is on the secondary side.

Sometimes a little error on primary side can effect some voltage on the secondary side. CMIIW.

how to check voltage on ic pins, is this means we check when connecting to the mains? is that possible with analog VOM at off conditions, i guess it is possible with DMM? i have same symptom with my PSU, it has a 2005Z IC
i didn't get a "power good" signal on gray colour rail. sorry for hijacking this thread just because have a same symptom.

Hi bro, nice to share here . I have another PSU with ATX2005Z PWM Controller which no voltage on Power Good.

what about +3,3V, did you forget to test it?

also please check voltage on weltend pins 1 and 16
and 9th pin on weltrened, should be less than 1.2

take some time to analyze the internal circuit of the chip to see what can cause PGO (pin 16) to be low

All voltage except Power Good are absolutely normal. Ok I try to analyzed the Weltrend IC. Thx for the link.

[Escort Eagle]

Re: power good 0v

I've read that in "Jestine Yong's handbook" and I replaced the cap with other, same capasity and bigger capasity I tried, but the problem not fixed.

If Primary Power signal is good then IC must drain the Power good signal . Primary power signal is good and still IC is not delivering power good signal, then IC must have problem . Normally PG problem occurs due to primary side's malfunction, not for secondary side . I have repaired several PSU with PG problem by replacing Primary Caps . Just for one case - I found defect on controller section in secondary side . Just a Resistor was visibly burnt there and the controller section was built with two ICs "TL494" and "LM339" . Otherwise every PG problem was solved by replacing caps .

I think - it may be a common problem of "WT7527" like as common problem of "TL494" is PWM problem .

[senz_90]

Re: power good 0v

hmm.. IMO i just think the IC has a problem. but the experienced one's can give you a better solution. btw please tell me how to check the ic voltage? i didn't get a datasheet for 2005Z ic around googling..where is Vcc and Vdd? and where is the pins that i should checking around...?

this is a good forum bro. you can improve your skill just searching the thread.. i am make a fast progress to understand SMPS design and how are they working after read many troubleshooting thread.

[everell]

Re: power good 0v

hmm.. IMO i just think the IC has a problem. but the experienced one's can give you a better solution. btw please tell me how to check the ic voltage? i didn't get a datasheet for 2005Z ic around googling..where is Vcc and Vdd? and where is the pins that i should checking around...?

Here is a drawing of the 2003/2005 chip

[Escort Eagle]

Re: power good 0v

Here is the Datasheet of ATX2005 .....

[senz_90]

Re: power good 0v

Thank you. btw AT 2005B didn't same with my ic configuration. the same one is by everell uploaded. My GND at pin 12, PG OUT pin 9, REF TL431 pin 10 11. btw what voltage that i have to expect? i have to search the datasheet internally configuration..

[eccerr0r]

Re: power good 0v

I had a deer PSU end up like that - produced volts but powergood was always 0V or around there.

In my case, a small ceramic filter capacitor (0.01uF) shorted near the powergood op amp. Replacing it restored operation.

I don't know how typical this is but it turned out to be the problem.

[senz_90]

Re: power good 0v

okay... i get this voltage each rails at pin:

1 = 7V
2 = 250mV
3 = 3.3V
4 = 4.8
6 = 350mV
9 = 130mV

is that normal?? i think pin 3 and 4 normal by the IC pict given by everell. but pin 2,6 and 9 has very low voltage.. any advise?

[domas]

Re: power good 0v

9 should be low, it's okay.
pin 2 is GND, it is supposed to have no voltage. There should not be any voltage between GND and that pin. Maybe there is a leak somewhere, i am not sure if 250mV is not normal, while it is only 0,25V.

I am not such an expert in open drain outputs, but pin 3 FPOB "Fault protection output pin, open drain output" should not have voltage if there is no fault, but i am an amateur in this.

check for dead diodes, resistors and caps around the chip

[senz_90]

Re: power good 0v

9 should be low, it's okay.
pin 2 is GND, it is supposed to have no voltage. There should not be any voltage between GND and that pin. Maybe there is a leak somewhere, i am not sure if 250mV is not normal, while it is only 0,25V.

I am not such an expert in open drain outputs, but pin 3 FPOB "Fault protection output pin, open drain output" should not have voltage if there is no fault, but i am an amateur in this.

check for dead diodes, resistors and caps around the chip

hm. i have check diode, resistor nearly, but it didn't show any leakage. maybe the caps or ceramic caps nearly.. i know the ceramic caps very seldom to broken but i have to check it i guess.. btw pin 6 should be 12V I think refer to IC pict?

[cheapie]

Re: power good 0v

(Looks like senz beat me to this...)

Isn't pin 6 supposed to be connected to +12V, according to the drawing?