Computer Power Supply

[gdurante]

Hello
I have a computer power supply which is dead.
The power supply is manufactured by OCZ model OCZ700MXSP.

After some troubleshooting I found a burned IC501. I cannot identify this IC because it is completely burned.
I was wondering if anybody can help me identify this IC, make any suggestions, and the possibility of getting my hands on a schematic of this supply.

Thank you

GD

[sam_sam_sam]

Re: Computer Power Supply

You need to post some photos of this power supply so we might be able to help you

[gdurante]

Re: Computer Power Supply

I shall do that ASAP.

Thank you for your help.

GD

[fzabkar]

Re: Computer Power Supply

It's not the same model PSU, but U501 appears to be a TNY278PN. I would trace your own circuit just to be sure, though.

TEARDOWN & REPAIR (we hope) of an OCZ MODXSTREAM-PRO 600W ATX PS:
http://www.eevblog.com/forum/repair/...o-600w-atx-ps/

IC501 --- TNY278PN, TNY274-280 Tiny-Switch III Family
https://cdn.badcaps-static.com/pdfs/...b56d9fb7b3.pdf

Schematic of standby supply (there is an error - the optocoupler is reversed):

http://www.eevblog.com/forum/repair/...;attach=130780


Google translation of OCZ repair thread:

http://webcache.googleusercontent.co...pic240740.html

It does not turn on, after the storm. Visually - "spaced" PWM duty room (IC501), the marking remains TN, very similar to TNY27x, I put TNY279 - silence, no output voltage, exploded analysis of defective components not identified. Consistently replaced optocoupler (U501), TL431 (U502). corrector power FAN4800IN (U201), in the absence of the original set CM6800G (it was the mention of such a change), - no effect. Question - how correct installation and TNY279 CM6800G.

Replacement 4800 6800 absolutely correct. It is identical crystals from different manufacturers.
4800 is not the corrector power - a PFC + PWM. It begins only after the duty room is OK. Even minor glitches in the duty room lead to malfunction 4800/6800.
To deal with the duty room. TN - is not only TNY 279, and 268, 278, etc. which is often used in the duty room of PD.
There was mention of the scheme at the PSU, but had disappeared, and all the links lead to "muzzle our site" on trippernye resources.

P.S. By the way - this PSU full analogue more common Hvirmy binders, namely FSP700-80GLC.
There used FSQ0270RNA duty room or FSDM0265R. And since PWM duty room data may have several functional analogs, including a pin and the pin, the fact that I was not surprised in this case applied any of TNY series.

In this case, the duty room, you can put a lot different.

[gdurante]

Re: Computer Power Supply

Thank you MAN DOWN UNDER for the superb repair info.
I know that with this info I can now repair my PSU.
Thank you. Any further suggestions would be deeply appreciated.
I have included some PICS of my PSU

THE CANADIAN

GD

[stj]

Re: Computer Power Supply

r506 is probably toast.

[gdurante]

Re: Computer Power Supply

R506 is OK it measures 2.2 ohms.

Diode D501 and ZD501 are also OK.

Any other ideas are welcome.

Question: is IC501 output power dependant? Example: for a 600W PSU IC501 is a TNY278PN. For a 700W PSU (Mine), is IC501 also TNY278PN?


Thanks

GD

[stj]

Re: Computer Power Supply

that chip afaik is for the 5v standby which is only 1-3a

[gdurante]

Re: Computer Power Supply

I replaced IC501 but as soon as I power up the PSU IC501 blows again. I started to troubleshoot further and found shorted D504 Schottky rectifier. I replaced the rectifier and IC501. Powered up the PSU (turned on the main switch in the back) everything is fine, as soon as I soft start the supply (power on computer) IC501 blows again but D504 is OK. At this point I am looking at T501.


I am stumped. Any suggestions?

Thank you

[stj]

Re: Computer Power Supply

so the 5v standby works,
but gets a BIG overload when you start the main supply.

maybe the main controller or pfc controller are shorted.

[gdurante]

Re: Computer Power Supply

Thank you for your quick response STJ. One thing I don't understand is why does IC501 blow when I turn on the main PSU if it is only used for the standby 5VDC?
I verified all the output diodes and caps..all OK no short. The main transformer is hard to check with a ohm meter. The only other thing I can possibly conclude is that the main PSU does not switch..possibly the main switching controller like you pointed out?
I will be looking closely at the input section.

[stj]

Re: Computer Power Supply

One thing I don't understand is why does IC501 blow when I turn on the main PSU if it is only used for the standby 5VDC?

it's often also used to power parts of the main supply to get it going

[gdurante]

Re: Computer Power Supply

Another update on my dead PSU

After further troubleshooting I discovered that all of the optocouplers (817BX) on the main board are defective. The input photodiode is open. There are 3 of them two for the main supply and one for the SB supply? How could this have happened? Overvoltage spike after a power failure maybe?

[gdurante]

Re: Computer Power Supply

update correction.
My DVM battery voltage was low therefore I could not forward bias the input photodiode. After replacing the DVM battery they all tested OK. I had my daughts?? at the same time I was optomistic. Back to the drawing board.

[everell]

Re: Computer Power Supply

You might be having a problem with the snubber circuit which is a diode, resistor, and capacitor across the primary of the 5vsb transformer. Sometimes the manufacturer uses a 1N4007 diode in this location, which works for a while. 1N4007 is a general purpose low frequency diode. What is needed is a HIGH FREQUENCY high voltage switching diode such as MUR2100EG rated for 1KV 2 Amps. From the photo, it looks like the diode in question is located next to R506.

If the snubber resistor is R506, 2 ohms is TOO LOW, should be about 33K to 47K. Read the color bands on that resistor to determine what the proper value should be. If it is NOT a snubber resistor, it could be a current limiting resistor in which case the 2 ohms value would be correct.

My suggestion is to trace your circuit board and determine which components are used for the snubber. Check them carefully and tell us what you find.

[gdurante]

Re: Computer Power Supply

I finally found my problem. The main filter cap 470Uf 400 volt read .66Uf on my fluke 76 DVM. Therefore I was getting unfiltered AC volts going to IC501 which was blowing the Sh.....t out of it. I replaced this cap with a 470Uf 450V and now the PSU is working just like new.
Thank you guys for all your valuable input.
Old proverb say....if at first you don't succeed, try, try, try again ( William Edward Hickson, 1840)

[dejan_bin_laden]

Re: Computer Power Supply

Hello, i have similiar psu with the almost same components inside, it burned the TNY278PN which i replaced, then i measured the R506 resistor it was giving 37kohms instead of 2 ohms soi replaced him also.
Finally i replaced the big cap 390uf 400V and still no power, everything else seems ok, anything else should i check before garbage ?

thank you

[G3n1us]

Re: Computer Power Supply

I had a Chieftek branded PSU with the exact same PCB. In this case, in addition to TNY278 and everything between it and the 5vsb transformer had exploded. Also the large Teapo filter cap was a dead short and because of it, diodes D101 and D102 failed shorted.

As a final cherry on top, the primary winding on the 5vsb transformer overheated and ruined the isolation between the winding layers.

(If anybody knows where that transformer can be sourced, please PM me!)