Silverstone ST1500 (+5Vsb shorted)

[selldoor]

Re: Silverstone ST1500 (+5Vsb shorted)

Here are the data sheets for the two chips on the riser board and the one you recently mentioned.

This supply will have PFC and so the voltage on the BIG caps should be
higher than what you have. If that is not working then nothing will work.
So perhaps you can read about these chips and do some tests.

[selldoor]

Re: Silverstone ST1500 (+5Vsb shorted)

This might be useful as well

http://www.jonnyguru.com/modules.php...tory4&reid=175

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

That chip is an NCP1200, which looks like your 5vSB controller. Pin 6 is its Vcc pin which is derived from an internal regulator that gets power from the main filter capacitors, and decouples with a small capacitor. (See example circuit page 2 in attached datasheet)

Pin 6 showing low ohms to ground does seem suspect. There are two capacitors (ceramic and electrolytic) on pin 6 to ground? The electrolytic is the one you changed?

Did you try testing the ceramic one for being shorted?
Pin 6 should have around 10volts on it when running, do you have this?

Pin 8 should have 300v or so from the primary capacitors.


Yes the primary filter capacitors are those 4 big ones rated 420 volts

Thanks mate , il remove that chip and check for short . I checked the ceramic cap and didnt any short .
No it doesnt get 10v when connected to power .

but pin 8 gets 300v.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

Here are the data sheets for the two chips on the riser board and the one you recently mentioned.

This supply will have PFC and so the voltage on the BIG caps should be
higher than what you have. If that is not working then nothing will work.
So perhaps you can read about these chips and do some tests.

Thanks mate , I went though them now , some parts is not clear for me.
I guess the short is made by a PC123 IC or the 200D6 chip .

The power supply part out was real helpful I searched all over internet and didnt find it .

THanks mate

[Agent24]

Re: Silverstone ST1500 (+5Vsb shorted)

If those capacitors aren't shorted then I reckon the NCP1200 is bad, even if the feedback opto was putting it into shutdown it should still have voltage on the Vcc pin.

Unless perhaps the transistor it drives is bad, that might do something

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

Thats what I'm thinking too . Il pull out the chip and see if the short is gone , you do you think its better to remove that too (transistor) ?

But im confused how a chip like this can short . I thought of buying this : here

THis is the correct one right .

What do you think about the pc123 IC ? can it be shorted ? does it have a chance to get shorted ?

[Agent24]

Re: Silverstone ST1500 (+5Vsb shorted)

Optoisolators can go bad but it's not common. You can test them pretty easily. http://www.antimath.info/electro/how...n-optocoupler/

The transistor is probably OK. If it was shorted I still don't think you'd lose Vcc unless it shorted Drain-Gate which would put high voltage back into the drive pin and could do anything. But since we don't know for sure, it's maybe a possibility. It wouldn't be hard to check in-circuit for shorts.

The one on eBay looks correct to me. I'd buy more than one though in case you need spares. Maybe this: http://www.ebay.com/itm/5PCS-200D6-N...-/390347621566 although if you can get them from a more reputable place than somewhere in China I would advise that, there are sometimes fakes\substandard parts from China

The IC may have seen some voltage spike on the HV input that blew the regulator, or maybe it just broke by itself. Some ICs just go bad. It happens.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

Optoisolators can go bad but it's not common. You can test them pretty easily. http://www.antimath.info/electro/how...n-optocoupler/

The transistor is probably OK. If it was shorted I still don't think you'd lose Vcc unless it shorted Drain-Gate which would put high voltage back into the drive pin and could do anything. But since we don't know for sure, it's maybe a possibility. It wouldn't be hard to check in-circuit for shorts.

The one on eBay looks correct to me. I'd buy more than one though in case you need spares. Maybe this: http://www.ebay.com/itm/5PCS-200D6-N...-/390347621566 although if you can get them from a more reputable place than somewhere in China I would advise that, there are sometimes fakes\substandard parts from China

The IC may have seen some voltage spike on the HV input that blew the regulator, or maybe it just broke by itself. Some ICs just go bad. It happens.

Hi mate , the PC123 seem to work . Its not hard to check for short but removing from the circuit is the problem because it mounted to a heatsink , infront of it I see big caps that wont let me unscrew the screw so I have to remove many components in that part to get the transistor out.

Il buy the one you suggested , because there may be broken ones too lol .
I cant find a place better than these chinese ebay guys because most of them ask a very high amount for shipping even though its a small part lol.


I removed the chip and now the short is gone. Now il have to wait till they send in the chip , il check for this locally to save some time . Or does old psu have this chip ?

[Agent24]

Re: Silverstone ST1500 (+5Vsb shorted)

Unfortunately I don't think it's a part that would be commonly found in old PSUs, just about everyone uses a different design for the 5vSB circuit. You can look but I wouldn't expect to find one.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

@Agent24
THanks mate , I can save time without looking because the psu's that I have are antique lol.
il try to find one locally.
il post back when I get my hands on one.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

Hey: that guy said he cannot ship to SriLanka so I found this: here
will this do the job ?
Also im ordering this: here
because the seller has both items and its just only 2$ also he can combine ship so I thought of buying it . Its the correct one right ?
THanks alot

[Agent24]

Re: Silverstone ST1500 (+5Vsb shorted)

It looks like the right part to me. (Correct number at least)

You may be able to get the opto-isolators locally though, or from an old PSU.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

It looks like the right part to me. (Correct number at least)

You may be able to get the opto-isolators locally though, or from an old PSU.

Thanks mate , I had a big doubt about it .
Yea , il check in some old psu , but il order this too in case I dont find it .

Il post back when items arrive , you guys are the best .

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

I was work less today so I though about connecting the chip to dc source to get a out put from vcc , I just connected this across the primary filter caps (300v dc) for few mins there was no output from the vcc but after a min like the vcc now puts out a voltage about 6v .
( the chip was connected to 8th ( + ) pin and 4th ( - ) pin ) . But I took it off the circuit and checked for resistance and it showed short circuit ?

[Agent24]

Re: Silverstone ST1500 (+5Vsb shorted)

Interesting, although I don't know how valid the test is since I assume you did not have feedback and current sense pins or anything else connected.

The datasheet explains the inbuilt power supply operation, but I am not sure how you could verify this without basically building one of the example circuits.

I guess in the mean time you could test other parts of the standby supply, check the MOSFET is OK, the rectifier, the feedback loop etc.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

Yea , I reinstalled it to psu , it makes a big short so I took it off now , I guess its somewhat broken lol .
Building a circuit will be a pain for me , because im out of parts .

I'm ordering a new mosfet (8N80) : here

I dont know even if its broken but im just replacing it just to avoid any shorts .
What terminals does it go short ? how can I find it (mosfet) ?

Also the rectifier seems to work ok from what I saw for now , because it gives a large reading and a small reading so I can assume its ok right ?

what do you mean by feedback loop ?
thanks mate

[stj]

Re: Silverstone ST1500 (+5Vsb shorted)

is the chip vcc conected to the main cap through some resistors?
if it is, check them with a meter.

back in the past i worked on psu's that ran that way - the resistors often went up in value and had to be replaced.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

is the chip vcc conected to the main cap through some resistors?
if it is, check them with a meter.

back in the past i worked on psu's that ran that way - the resistors often went up in value and had to be replaced.

No its not connected to main cap , but from the main cap line the vcc is made by the chip itself .

yea , but I see large resistors have very low resistance like 2ohms , why is it ?

[stj]

Re: Silverstone ST1500 (+5Vsb shorted)

probably so it can detect the current flowing through it.

[new2019]

Re: Silverstone ST1500 (+5Vsb shorted)

Yea , but the pin 6 cannot be shorted to ground right ? that shows a fault in the chip right ?