Antec High current Gamer 750w - restored from death ! But !

[datoska]

Introduction :


hey guys ! I'm new here,for long time I was just reading threads and absorbing information ...
but its time to do something...

my bio:
I live in Georgia(its not so wealthy country, so people here try to just survive and feed themselves)
I have small buisness, basically I'm buying computer parts in USA, then ship them to georgia, and sell them here... with that, I make about 140-150$ a month (i'm 19 years old at this moment, and studying energetics in Georgian technical university... probably need to study english a bit more...)
well.... umm, ah yeah ! sometimes "bad" sellers sand me non working components, in most cases thay are power supplies, I cant ship them back to usa because it costs twice as much as psu itself, so I'm just trying to fix them... make modular cables from non modular power supplies and etc...

more to the point ----------------

Several days ago I got just dead "Antec High current Gamer 750w (HCG-750)"
disassembled it, and first what I found out, was blown fuse, as we all know fuse doesnt die by itself, so i just changed fuse to new one, and powered psu from "UPS surge",turned psu switch on, BEEEEP!....UPS light indicator says "OVERLOAD",well we have short circuit here....
long story short:except bad fuse, I found dead Diode(no outter damage, like burned spots, etc...) and one bad MOSFET(again no outter damage).
I had several scrap psus (all from 600w to 1200w (thermaltake,PC P&C silencer, rocketfish,Tagan etc..)) so I took exact same diode from Rocketfish 750w soldered it onto antec, then found similar mosfet on rocketfish, desoldered it and appears it's 20n60c3, but we need 24n60c3 ... well, so i just took 20n60c3 and soldered onto antek psu, assembled everything, turned on, whoa ! it works , tested only 12v and 5v rails, they were 12.4v and 5.2v.... BUT ! here is a problem , first everything worked well , then pc suddenly shutted down, turned pc on again, and i hear that HDD sometimes loses power and computer reboots by itself...
several days ago ran Everest Stability test, it was passing ok for about 4-5 hours, then I just opened chrome, and pc shuts down...

Question : any idea whats going on? is that mosfets fault ?
any kind of answer/suggestion is highly appreciated !

[ReeceyBurger123]

Re: Antec High current Gamer 750w - restored from death ! But !

Is the Pfc bus voltage working ? The mosfet changed and the diode are for the Pfc.

[datoska]

Re: Antec High current Gamer 750w - restored from death ! But !

Is the Pfc bus voltage working ? The mosfet changed and the diode are for the Pfc.

have no idea what that means.... how much must it be ? 5V ?

[Per Hansson]

Re: Antec High current Gamer 750w - restored from death ! But !

When the PSU is soft off the PFC circuit will not be running so on the primary capacitor you will have: √2 x 220VAC = 311VDC (With 115VAC it would be 163VDC)
When you start the PSU the PFC circuit will boost the voltage to whatever it is designed for, usually right up around 400VDC.
So that is what ReeceyBurger123 asked you to check, of course it applies here to say:
Be EXTREMELY careful, 400VDC on a cheap meter might cause it to blow up, and if you get in contact with 400VDC yourself you can imagine what will happen (human beings are not compatible with high voltage!)

[datoska]

Re: Antec High current Gamer 750w - restored from death ! But !

When the PSU is soft off the PFC circuit will not be running so on the primary capacitor you will have: √2 x 220VAC = 311VDC (With 115VAC it would be 163VDC)
When you start the PSU the PFC circuit will boost the voltage to whatever it is designed for, usually right up around 400VDC.
So that is what ReeceyBurger123 asked you to check, of course it applies here to say:
Be EXTREMELY careful, 400VDC on a cheap meter might cause it to blow up, and if you get in contact with 400VDC yourself you can imagine what will happen (human beings are not compatible with high voltage!)

Well yeah 400v is deadly for human beings. I carefully tested voltage on idle it was 290 not 311... And when i turned psu on it geve 392v. Is that normal?

[Behemot]

Re: Antec High current Gamer 750w - restored from death ! But !

Yeah that is within tolerance (the line is usually +-20 V). You may have lower line voltage a bit, also there are some losses on the rectifiers etc.

Any strange noises from the unit? That would indicate persistent PFC problem. Also check the orange film cap in the corner and the others, they sometimes go bad and as it is used in the PFC circuit…

Also a problem may be in the PFC coil. This is unit from Delta, they started using these coils with two sepparate windings, I have been told for security reasons or whatever. I am not exactly sure how it works, but if both windings are supposed to have same inductance and one may have shorted a few turns or something…that it may be broken.

[Per Hansson]

Re: Antec High current Gamer 750w - restored from death ! But !

Well yeah 400v is deadly for human beings. I carefully tested voltage on idle it was 290 not 311... And when i turned psu on it geve 392v. Is that normal?

Yes it's fine, I showed you the calculation for that.
Just measure your line voltage at the same time as you take the reading on the PSU.
Then the square root of two times what line voltage you had should equal what you read on the primary capacitor.
(But It's mostly academic now, the voltages you reported are fine so problem is likely elsewhere).

[datoska]

Re: Antec High current Gamer 750w - restored from death ! But !

Behemot
Thanks again for the answer ! community looks just awesome here !
well ok, I will check capacitors there (my multimeter can measure no more than 200uf(mkf)... and that really annoys me, i'm going to order http://www.ebay.com/itm/LCR-T3-graph...EAAOSwpDdVZIPW
it measures up to 100 000uf(mkf), and also has cool features...)
no weird noises too(like coul whine, I just stopped cooler, and no noise at all, may be because load is too low ? about 100w...) , I havent had this psu in the past, but cooler spins really loud compared to other brands I have at this moment ( rosewill,antec,Raidmax...
you can see them here under red writing spoiler...
https://forum.ge/?act=ST&f=54&t=34845309)

Per Hansson
thanks for calculations ! it's really handy!
will consider this in future repair works !



-----------------------------------------------------------------------------
I also have dead thermaltake 750M power supply, there were 2 dead mosfets, also 1 dead power diode, one big cap, one 15ohm resistor, and whole external pfc chip burned with smd 550kohm resistor.... but thats whole other story... I changed mosfets with power diode,big capacitor 15ohm resistor, AND whoa ! it now shows 5vsb ! but again... this will be posted here in future...

[datoska]

Re: Antec High current Gamer 750w - restored from death ! But !

after writing my last comment I searched for clues on russian forums, one guy was talking about SilverStone 1200W, he had the same problem as me, he discovered that all 2200х16 caps were inflated, he changed them and psu started working normally... so my question has born there, I have various scrap capacitors from dead power supplies, some labels say 16v 22uf, but when I measure it says 15uf.... is that normal ? whats average % difference between label and reality?
and good to know which capacitor brand names are good ?

[Behemot]

Re: Antec High current Gamer 750w - restored from death ! But !

I personaly don't like these generic AVR meters (they are all garage-made version of that german open-source meter). Just got a new version from Radiodevices ATM for testing, it seems more interesting than the previous one, but still I will only have that as additional device. For caps I only use ESR Micro as these meters are useless to measure in-circuit.

But meter won't tell you much in this case anyway as these caps have very low capacity and sometimes they fail (cracks have been spotted) without meter recognizing it - at least with their small voltage they use to measure (couple volts at most). Than they behave differently on line voltage, which is sometimes enough to create dielectric breakdown.

As for caps, if they go bad, they often loose capacity. Rated value is usually +-20 %. But ESR is equally important to capacity.

[datoska]

Re: Antec High current Gamer 750w - restored from death ! But !

Behemot

checked that red film capacitor in left upper side, it shows 1.3uf it's rated at 1.5uf. so I guess problem is elsewhere... also checked all capacitors, neither of them look bulked or cracked...
cant measure more than 200uf, so basically my multimeter is useless at this moment...

"Also a problem may be in the PFC coil. This is unit from Delta, they started using these coils with two sepparate windings, I have been told for security reasons or whatever. I am not exactly sure how it works, but if both windings are supposed to have same inductance and one may have shorted a few turns or something…that it may be broken."

also about pfc coil, i'm not sure how can I measure inductance(i have oscilloscope,laboratory power supply,multimeter).
I have put my multimeter on diode test and checked coil, everything looks ok, no shortage between two saperate windings...?

[charis]

Re: Antec High current Gamer 750w - restored from death ! But !

To rare to be the coil failure.
If you have continuity its ok you need a LCR Meter to measure them.
I think that the switching ic on psu is faulty.Check the pulse in the output pin.(use isolation transformer)to probe.
Find the code and see the datasheet .
Also check that the ic have no cold joints.

[Behemot]

Re: Antec High current Gamer 750w - restored from death ! But !

This one has two windings, and I have no idea how they are exactly wired. That AVR meter can measure this, out of circuit…

[datoska]

Re: Antec High current Gamer 750w - restored from death ! But !

Charis

Thanks for reply, I will check ic for cold joints.. But i dont think that there are those... Antec is pretty good at soldering. But still good thing to check it..

Also im not sure how to test IC output pin with isolated transformer.. Could I use osciloscope?


Behemot

Yeah AVR meter would be cool, but i will have it after 20-25 days or might more...
And yeah i dont think that coil could be damaged, it has so large awg wires that fuse would blow two times to burn that coil... Well... AT THIS POINT, I DONT THINK THAT ITS POSSIBLE..

[charis]

Re: Antec High current Gamer 750w - restored from death ! But !

I dont have the schematic the manual show only the monitor of the rail ic which is after the regulation circuit.
This ic watch all the 4 rail voltages(+12 +3.3 +5 -12) a very nice feature.
I talk about the switching controller ic on on primary side of the circuit.
You can use a oscilloscope to check for output pulses an isolation transformer is a must have item as it isolates the psu from the mains so you can connect your scope to the psu...without it as soon as you connect the ground from your scope and switch on there will be a bang and you will create more work for yourself .
hot ground refers to the primary side of your smps(switch mode powersupply),cold ground refers to the secondary side of the supply-connecting the scope ground to the smps hot ground and expecting to check waveforms for the line stage is a waste of time(an example),you need to know how to connect things for taking SAFE measurements on any eqipment .
You can see this at many pcb you have a black fat line to show you were the cold and where the hot side.
If not you can see the optocoupler that bridge the two sides for monitor purposes.

[Per Hansson]

Re: Antec High current Gamer 750w - restored from death ! But !

you need to know how to connect things for taking SAFE measurements on any eqipment .

Connecting a scope to an isolation transformer is the opposite of "SAFE measurements"
When you do it that way the scopes chassis, the BNC connectors etc etc will be at the potential of the circuit you are probing.
Touch the wrong thing and boom you're dead.
Use a differential probe if you need to probe circuits like this.