Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

[rodd]

Dear all,
I am trying to repair the ATX power supply.
First I fixed the +5V stby, which was zero due to a shorted TNY279 and an open 2R2 resistor.

Just in case I replaced the PWM control IC (PS223) and the PFC control IC (CM6800).

Now the supply turns on, the +3.3V is fine, but the +5V measures only 2.5V and there is no +12V.

I have checked every diode I could find with a DMM (in circuit) and all the capacitors (in circuit) no shorts, low ESR.
In despair I removed the low voltage diodes which were all mounted on the same heatsink to test the out of circuit; all teste GOOD.
I used a bench power supply adjusted to the value of each voltage rail and connected it to the PS outputs- the current "drain" was low in every case, so no shorts.

I ran out of ideas. Any suggestion?
Thanks

[CapLeaker]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Kinda hard to believe that the supervisor will actually allow this to happen. It just should shut down the primary. Does the PFC work?

[R_J]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Re check your work around the other parts you replaced,

Just in case I replaced the PWM control IC (PS223) and the PFC control IC (CM6800).

maybe the replacement parts are bad?
See if this thread helps https://www.badcaps.net/forum/showthread.php?t=51160

[stj]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

on the 5v rail it's obviously an issue in the feedback section.
12v - not so simple

[labello]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Dear all,
I am trying to repair the ATX power supply.
First I fixed the +5V stby, which was zero due to a shorted TNY279 and an open 2R2 resistor.

Just in case I replaced the PWM control IC (PS223) and the PFC control IC (CM6800).

Now the supply turns on, the +3.3V is fine, but the +5V measures only 2.5V and there is no +12V.


I have checked every diode I could find with a DMM (in circuit) and all the capacitors (in circuit) no shorts, low ESR.
In despair I removed the low voltage diodes which were all mounted on the same heatsink to test the out of circuit; all teste GOOD.
I used a bench power supply adjusted to the value of each voltage rail and connected it to the PS outputs- the current "drain" was low in every case, so no shorts.

I ran out of ideas. Any suggestion?
Thanks

Hello well it's hard work to resolve your problem, but if I was you I'll start to check the size with high voltage, of course "another person here tell you already " But you must check everything better out of circuit , you know capacitor, bridge rectifier Mosfett ,diode rectifier and others, then keep going on the safe place( low voltage). I hope to give you right line. If you need something else I'm here..

[labello]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Hello well it's hard work to resolve your problem, but if I was you I'll start to check the size with high voltage, of course "another person here tell you already " But you must check everything better out of circuit , you know capacitor, bridge rectifier Mosfett ,diode rectifier and others, then keep going on the safe place( low voltage). I hope to give you right line. If you need something else I'm here..

I'm here again I almost forgot to tell you that (be sure your PFC work properly because if it doesn't your power supply will not work !

[rodd]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

After fixing the +5V Stby and replacing the CM6008 the voltage across the main cap raised from 175V to 385V, so I guess that the PFC section is working fine.
Is there any other thing I should check?

[CapLeaker]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

What supervisor does it have? I guess the PFC is working fine.

[labello]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

After fixing the +5V Stby and replacing the CM6008 the voltage across the main cap raised from 175V to 385V, so I guess that the PFC section is working fine.
Is there any other thing I should check?

Well if you " guess " the PFC is working well there's not be any problem .So why we continue to talk about if you don't pay attention of indication to solve your problem..?

[rodd]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Hi,
I did not mean to offend anybody, I have just described what I have done and my observations.

After I fixed the +5V Stby, the PS could start but the PS monitor I used was beeping.
Checking its display I could see that the +12v and +5V was showing LL, but 3.3V rail was ok.
So my line of thought is that the main oscillator is working.
However if the 5V and 12v rails voltages are low the PS223 should have turned the main oscillator off.
This IC is mounted on a small pcb on the "side" of the power supply, on a socked.
I replaced the supervisor (PS223) and the PFC (CM6800), but the readings did not changed.
Maybe the replacement IC is broken, as suggested before on this thread.

Does anybody has the schematics of this power supply or any similar that I could use as a reference for continuing the troubleshooting?
That would help a lot!!

My next step would be installing the diodes back in the main PCB and use a scope to measure the waveforms at the PS223 out, Primary and secondary main transformer.
Thank you all for the replies given so far.

[CapLeaker]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Maybe post some clear, straight shot, high resolution pictures front and back of the PSU.

[rodd]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

These are photos from top and bottom.
The heatsink with the rectifier diodes of the secondary has been removed so I could check them out of the circuit.

[CapLeaker]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

The supervisor should have disabled the primary which it didn’t. Why I don’t know. If the FPO pin is high, a fault is detected. To disable the supervisor, all you have to do is to ground out that FPO pin. If it still doesn’t work the problem is either still that cm6800 which I doubt but not rule it out, or there is a short on one of these voltage rails in the secondary. Weird thing is why the supervisor isn’t able to shut the psu down, as it should get VCC from that 5V stby rail. All the other voltages are just monitored by it. Well, time will tell after you measure that FPO pin.

[labello]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Neither I . My question was about you (guessing) . Generally to repair electronic you must test everything find the problem and be sure that will be fixed properly, therefore it must be reason why blown up the smd that you changed. Generally power supply works about generating voltage in different ways. So be sure to check everything is fine and change what is wrong with it then it will work again!

[labello]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Yes I think the same way about (Some Short) but if he continued to (guessing) he never find the real problem so it will remain unfixed...

[rodd]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Hi,
More news from the "front".
I inslalled the PS223 backwards again and the PS starts and all the voltages are ok.
This means that the CM6800 and all "power semiconductors" are ok.
So I guess that the problem is located on the small pcb where the PS223 is installed.
As I asked in my previous post, I do not understand very well how the PS223 works but it seems that installing it bacwards causes the ok signal to be present.
I have already checked every resistor (on board) and the readings seem ok.
The there are two to92 devices and one diode on the component side.
unfortunately the markings of one of the devices is covered by glue, so I can't tell if it is a transistor or a 3 pin reference.
There is also a smd zener diode which I don't know what is its zener voltage but it tested good as a diode.
Is there a schematics available for this board?
Any idea of what might be triggering on the FAULT status if it seems that there is no short at the outputs?
Note: I have measured the resistance of every rail to ground and I am sure there is no short in the voltage rails.
Thanks.

[rodd]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

[QUOTE= Weird thing is why the supervisor isn't able to shut the psu down, as it should get VCC from that 5V stby rail.[/QUOTE]
I installed the IC backwards, that's why.
After I replaced another dried capacitor, al volatges are ok, but the PSU does not start if I install a new IC in the correct position

[CapLeaker]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

if you ground out the FPO pin from the PS223 supervisor, all it does is disable all the supervisory functions. Basically if something is wrong in the secondary like over voltage or over current or a blown diode / missing voltage rail, the PSU cannot turn off.

So either there is something wrong with the little supervisor board, a cold solder joint, a solder bridge, a bad PS223 supervisor IC (even so it is new) or something else on the monitoring circuitry on the secondary. I always order at least 2 IC's just in case.

When you had that supervisor installed backwards, all the voltage rails were up and running?

[rodd]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v FIXED

Thank you all for the replies.
I could fix it!
There were two problems after I fixed the 5V stby rail.
1 - I damaged the PS223 by installing it backawards
2 - I broke my thermaltake power supply tester during the tests, so the start button in it won't start the PS.
This one was very difficult to pinpoint since I thought that the fault was in the power supply, not in the tester

[CapLeaker]

Re: Thermaltake TR2 750W -fixed 5v stby now +5v reads low and no 12v

Glad you were able to get to the bottom of this and fix it!