Excellent power model IT ATX 300w - shuts down after a split second

[kotel studios]

Hmmm.. that's not right.
Are you sure you measured pin 11 (maybe you're getting it confusing with another one when you flip the PCB)? If you are sure you measured pin 11, let's simplify this test a little bit and re-do it. I already did it on my PSU just to verify, and the results were as I expected them to be. So here's how to proceed:

1) Instead of having PSU plugged in the AC, just feed 5V into the 5VSB rail (probably best to use another ATX PSU, because you will be injecting another voltage concurrently, soon.)
2) Verify that pin #1 of the PWM IC is getting 5V - the same voltage that you read on your 5VSB line (please specify in your response what it is too, as this might skew the results a little.)
3) Inject 3.3V into the 3.3V rail and verify that you can read 3.3V on any of the orange wires when doing so.
4) Check the voltage of pin #11 (VREF) of the PWM IC and report back what it is. It shouldn't be in the mV range. It should be in the Volts range.


Maybe.
At the very least, the primary BJTs out of that one might come in handy for testing the Tagan PSU... but that's another story.


Just FYI: 520 Ohms and 41 Ohms are not standard values.
On my PSU, R58 is [blue, red, brown, gold].... 620 Ohms (a standard resistor value according to E24 standard codes).
And R31 I have as [yellow, purple, black, gold]... or 47 Ohms... which your reading of 47 Ohms confirms it's probably fine.

Another testing tip: resistor usually almost always show lower resistance in circuit... or at most, the same value that is specified by its color code (and maybe plus the added tolerance... e.g. a 100 Ohm resistor can read as high as 105 Ohms if it's 5% tolerance type.) Now, if a resistor does test higher resistance in circuit than what is specified by its color code (and tolerance spec), then it probably is bad or marginal. But again, if you read lower resistance, that's usually OK.


Well, no, this won't work, because once you insert "good" voltages into the PWM IC, it won't bother telling the primary side to run (much... if at all). So this won't test neither the primary side power components, nor the secondary side power components.

On the other hand, that "destructive" test I suggested is different. By using the PWM driving signals of another PSU (and injecting them directly at the two totem-pole pins of the middle transformer), the Excellent PSU's primary side BJTs will be instructed to run according to the other PSU's signals. This means that even if there is a fault on the secondary side of the Excellent ATX PSU's, it will not see it and not care, because there's essentially no feedback. The usefulness of this approach is that you will see whether the primary side is capable of switching and staying running... and if the secondary side power rectifiers will produce any voltages. The voltage rails might not be at their proper values (i.e. 5V might be 4V or even 3V or 7V... and likewise with the 12V)... but they should all at least be proportional to each other - e.g. if 5V is 20% higher (6V), then you can expect the 12V rail to also be 20% higher (14.4V). Only the 3.3V may regulate properly, due to being an independent regulation (mag-amp) circuit... unless its supply line (5V rail unrectified) drops too low - then it may not be able to regulate at 3.3V. But either way, all of these rails should output something / some voltage and be stable at it.

But let's leave the "destructive" test for now. Even with the dim bulb device, there's a lot that can be misconfigured to go wrong.

From my knowledge pin 11 is on the side with the 2003 written on it, not on the full model markings (and where the PS_ON is). So yes, fairly certain I did measure pin 11 correctly.
I'll report the findings of the tests once I get back to my workshop.
Finding the primary BJT's is gonna be hard due to me having put them in two different parts bin.... Although the PWM chip looks to be the ATX 2005, gonna make sure its not the "b" variant.
Okay I made a mistake while reading R58 (don't know why but I forgot about green band before blue ). But R31? I think its yellow brown black gold, or maybe it overheatead too much and the purple turned brown? (there are visible signs of overheating).
Yeah, let's leave the destructive test as a last resort...

[kotel studios]

Actually, looking at what's written on the post about those PWM's it's not possible to change the 2003 with 2005 PWM IC due to functions of pins 1 and 6.

[kotel studios]

I get 4.9v on pin 1 while injecting 5vsb. I also noticed I get 1.04v while injecting 5v on pin 11. Although when I inject 3.3v its still 49mV....

[momaka]

Actually, looking at what's written on the post about those PWM's it's not possible to change the 2003 with 2005 PWM IC due to functions of pins 1 and 6.

Correct.

I also noticed I get 1.04v while injecting 5v on pin 11. Although when I inject 3.3v its still 49mV....

No, don't inject 5V into pin 11. Only inject 5V into 5VSB and 3.3V into 3.3V rail (simultaneously). When you do that, you should see/measure 2.5V at pin 11 of the 2003 PWM IC with your multimeter (relative to ground). This tests that the PWM IC's shunt regulator is working. It doesn't make sense that you're getting a higher voltage (1.04V) when you're not injecting anything in the 3.3V rail than when you are. Double-check your measurements and setup. FWIW, pin 11 is the one right next to the orange 3.3V Sense wire.

[kotel studios]

No, don't inject 5V into pin 11. Only inject 5V into 5VSB and 3.3V into 3.3V rail (simultaneously). When you do that, you should see/measure 2.5V at pin 11 of the 2003 PWM IC with your multimeter (relative to ground). This tests that the PWM IC's shunt regulator is working. It doesn't make sense that you're getting a higher voltage (1.04V) when you're not injecting anything in the 3.3V rail than when you are. Double-check your measurements and setup. FWIW, pin 11 is the one right next to the orange 3.3V Sense wire.

I'm injecting 5v into 5vsb and 3.3v into 3.3v. Not to the pin 11 of PWM IC. Sorry for the confusion.
I'll recheck if I'm measuring the pin 11, but both of the surrounding pins show 0v. Or I am remembering something wrong.

[kotel studios]

While injecting 3.3v I noticed 3.3v rail only pulls 3v instead of 3.3v set. 3.3v sense seems to get its voltage (2.89v). While the pin next to it facing the fan gets 2.35v, so I did measure the wrong pin.
Any ideas?

[momaka]

While injecting 3.3v I noticed 3.3v rail only pulls 3v instead of 3.3v set. 3.3v sense seems to get its voltage (2.89v). While the pin next to it facing the fan gets 2.35v, so I did measure the wrong pin.

That sounds a lot more reasonable.
You're only getting 3V on the cable probably because of voltage drop over the cable. You can increase the 3.3V supply from your bench PSU slightly to make up for that, so you get as close as possible to 3.33V when measured directly at the orange wires of the Excellent ATX PSU. With that, you'll probably get very close to 2.5V on pin 11. If you like, you can redo that test... but for all practical purposes, it looks like the feedback for the 3.3V rail shunt regulator is working here.

Next test, back feed all of the voltages from another ATX PSU into the Excellent ATX PSU: that is, 5VSB, 3.3V, 5V, 12V, -12V, and -5V. After this, measure voltage on the PWM IC of the Excellent ATX PSU for the following pin (with respect to ground) and post the results here:
PIN 1
PIN 2
PIN 3
PIN 4
PIN 5
PIN 6
PIN 7
PIN 8
PIN 9

After this, with everything still powered up and the other PSU back-feeding into the Excellent ATX PSU, short PS_ON (green wire) to ground on the Excellent ATX PSU and retake the above measurements (for pins 1 through 9). Report those too.
This should give us a fuller picture of what the PWM IC is doing.

[kotel studios]

One more thing, pin 1 is on the side closer to the APFC transformator, right? And then the one next to it is 2, and 3 and so on...
or does it go pin 1 and pin 2 on the opposite side?

[kotel studios]

From top to bottom, not shorting ps_on
PIN 1 - 4.95v
PIN 2 - 2.35v
PIN 3- 3.35v
PIN 4 - 4.92v
PIN 5 - 24.8mV
PIN 6 - -0.67v
PIN 7 - 650mV
PIN 8 - 640mV
PIN 9 - 150mV

With ps_on shorted
PIN 1 - 4.95v
PIN 2 - 0.27V
PIN 3 - 3.32v
PIN 4 - 4.92V
PIN 5 - 24mV
PIN 6 - 0.67V
PIN 7 - 650mV
PIN 8 - 640mV
PIN 9 - 0.15mV

All of this was done without mains connected.

[momaka]

One more thing, pin 1 is on the side closer to the APFC transformator, right? And then the one next to it is 2, and 3 and so on...
or does it go pin 1 and pin 2 on the opposite side?

Well, you got pin 1 right, looks like, as you got 5V there.

But just so I can validate the values of these voltage, here's how the pins go below (and please tell me if this is how you counted them or not):
When you look at the PWM chip on the top side, rotate the board so that the notch on the chip is oriented to the left.When you do that, the "2003" on top will be exactly like you see it / can read it.
With this orientation, pin 1 is at the lower left corner. Going to the right one pin is pin # 2, then # 3, and etc. until you reach pin # 8, which will be at the lower-right corner of the chip. Then you jump across, to the upper-right corner of the chip - this is pin # 9. Going left to the pin next to it is pin # 10, then 11, and etc. until you get to the upper-left corner, which is the last pin - pin # 16.

Please let me know if this is how you counted the pins.

From the voltages you posted, your PS_ON signal at pin # 2 looks a little low to me (when not shorted to ground). On my PSU, it's only about 0.2-0.3V less than the voltage at pin # 1, Vcc.
The voltage on pins 7 and 8 are also low compared to my chip, both in the "Off" state and in the "On" state of the PS_ON signal. On mine, I was getting close to 1.2V (about twice as high as yours.) Check diode D19 (right behind Q6) once more... or better yet, just replace it. Also, with the PSU unpowered (AC power removed), what resistance do you get to ground on pin 7 and pin 8?

Most importantly, what really isn't right from the above voltages is the one at pin # 6. This is the 12V rail sense input. It's tied to the 12V rail through a 47-Ohm resistor, R31 (which is close to R47, which itself is close to Q6 and fan connectors CN3 and CN4.) Please re-check this resistor again. It's hard to believe how you may be injecting 12V into the 12V rail and not getting almost close to 12V at pin # 6 of the PWM IC. To me, this suggests either R31 is open or there is a cut in the trace somewhere going from the 12V line to R31.

[kotel studios]

Well, you got pin 1 right, looks like, as you got 5V there.

But just so I can validate the values of these voltage, here's how the pins go below (and please tell me if this is how you counted them or not):
When you look at the PWM chip on the top side, rotate the board so that the notch on the chip is oriented to the left.When you do that, the "2003" on top will be exactly like you see it / can read it.
With this orientation, pin 1 is at the lower left corner. Going to the right one pin is pin # 2, then # 3, and etc. until you reach pin # 8, which will be at the lower-right corner of the chip. Then you jump across, to the upper-right corner of the chip - this is pin # 9. Going left to the pin next to it is pin # 10, then 11, and etc. until you get to the upper-left corner, which is the last pin - pin # 16.

Please let me know if this is how you counted the pins.

From the voltages you posted, your PS_ON signal at pin # 2 looks a little low to me (when not shorted to ground). On my PSU, it's only about 0.2-0.3V less than the voltage at pin # 1, Vcc.
The voltage on pins 7 and 8 are also low compared to my chip, both in the "Off" state and in the "On" state of the PS_ON signal. On mine, I was getting close to 1.2V (about twice as high as yours.) Check diode D19 (right behind Q6) once more... or better yet, just replace it. Also, with the PSU unpowered (AC power removed), what resistance do you get to ground on pin 7 and pin 8?

Most importantly, what really isn't right from the above voltages is the one at pin # 6. This is the 12V rail sense input. It's tied to the 12V rail through a 47-Ohm resistor, R31 (which is close to R47, which itself is close to Q6 and fan connectors CN3 and CN4.) Please re-check this resistor again. It's hard to believe how you may be injecting 12V into the 12V rail and not getting almost close to 12V at pin # 6 of the PWM IC. To me, this suggests either R31 is open or there is a cut in the trace somewhere going from the 12V line to R31.

About the 12v sense the trace was indeed cut. I have only soldered the fan connector to 12v rail, not past it. Now I get 11.84v on pin 6.
Yes, I measured the pwm ic like you said.
Both pin 8 and 7 measure 503ohms to gnd. D19 has 700mV and 2pF in capacitance according to my lcr t7. Besides it only has the band marking the anode on it, nothing more so I don't know what to replace it with.

[kotel studios]

About the 12v sense the trace was indeed cut. I have only soldered the fan connector to 12v rail, not past it. Now I get 11.84v on pin 6.
Yes, I measured the pwm ic like you said.
Both pin 8 and 7 measure 503ohms to gnd. D19 has 700mV and 2pF in capacitance according to my lcr t7. Besides it only has the band marking the anode on it, nothing more so I don't know what to replace it with.

I have forgot to mention the PSU still doesn't power on with AC connected, even the fan doesn't twitch slightly anymore (it still spins fine with 12v injected).

[kotel studios]

Since I dug out my (working) excellent power 400w PSU from an old PC I was doing maintenance on I decided to see what type of diode was D19. I think it is a normal 1n4148 zener, so I replaced it with an new one on the patient. I also redid the measurements on pin 7 and 8 and both have around 1.6v on both of the PSU's now when AC is connected. Although the patient 300w PSU still doesn't wanna start up. So I backfeed the patient without mains connected once more and.... inside is an cheap chineese crap burning smell..... I don't recall encountering this issue before, but it is an distinct smell (like an blender burning out). I am unsure what to do now. I could give my hopes up now and dunk it, or do as you've said to bypass the whole primary side and watch the secondary side burn.

[momaka]

So I backfeed the patient without mains connected once more and.... inside is an cheap chineese crap burning smell..... I don't recall encountering this issue before, but it is an distinct smell (like an blender burning out). I am unsure what to do now. I could give my hopes up now and dunk it, or do as you've said to bypass the whole primary side and watch the secondary side burn.

Not yet!
I think we are just starting to hit the problem right now.

First, check that resistor R31 (47 Ohm) again. Maybe that's burned out, or starting to, with the 12V being backfed.

... I decided to see what type of diode was D19. I think it is a normal 1n4148 zener,

Correct, it's a regular 1n4148 indeed.

Have a look (again) at this simplified schematic from the KDMpower thread again (it's of a Raidmax RX-380k PSU):
https://www.badcaps.net/filedata/fetch?id=2058927

In your case above, D19 corresponds to D25 on that Raidmax schematic, and there is no 2nd diode above it on your PSU like there is in the diagram. Instead, D19 anode connects to the Emitters of Q5 and Q6 in your PSU.

so I replaced it with an new one on the patient. I also redid the measurements on pin 7 and 8 and both have around 1.6v on both of the PSU's now when AC is connected. Although the patient 300w PSU still doesn't wanna start up.

OK, but that's a good start.
1.x Volts is a lot more inline with what I expect to see here. The reason why is because you have the Base-Emitter junction voltage drops (about 0.6V) on Q5 and Q6 plus the voltage drop from D19 (also around 0.6V)... so at minimum, that's 1.2V, which is what I have on my PSU. 1.6V on yours actually seems a bit high, so not sure why that is, so check again. In any case, this is much better than the 0.7-0.8V you had before.

In terms of resistance, around 500 Ohms is correct - I just double-checked with mine.

That said, perhaps it's also possible that the middle driver transformer could have burned out or gone bad. One way to know is to try replacing this transformer with the one from the Logic Concept LC-B300ATX PSU you have. They are both Deer/Allied/L&C units, so parts should be interchangeable more or less. Just doubt-check the pinout of the transformers matches, and if not run with short wires like I did here for the KDMpower PSU:
https://www.badcaps.net/filedata/fetch?id=2058932
.

[kotel studios]

Not yet!
I think we are just starting to hit the problem right now.

First, check that resistor R31 (47 Ohm) again. Maybe that's burned out, or starting to, with the 12V being backfed.


Correct, it's a regular 1n4148 indeed.

Have a look (again) at this simplified schematic from the KDMpower thread again (it's of a Raidmax RX-380k PSU):
https://www.badcaps.net/filedata/fetch?id=2058927

In your case above, D19 corresponds to D25 on that Raidmax schematic, and there is no 2nd diode above it on your PSU like there is in the diagram. Instead, D19 anode connects to the Emitters of Q5 and Q6 in your PSU.


OK, but that's a good start.
1.x Volts is a lot more inline with what I expect to see here. The reason why is because you have the Base-Emitter junction voltage drops (about 0.6V) on Q5 and Q6 plus the voltage drop from D19 (also around 0.6V)... so at minimum, that's 1.2V, which is what I have on my PSU. 1.6V on yours actually seems a bit high, so not sure why that is, so check again. In any case, this is much better than the 0.7-0.8V you had before.

In terms of resistance, around 500 Ohms is correct - I just double-checked with mine.

That said, perhaps it's also possible that the middle driver transformer could have burned out or gone bad. One way to know is to try replacing this transformer with the one from the Logic Concept LC-B300ATX PSU you have. They are both Deer/Allied/L&C units, so parts should be interchangeable more or less. Just doubt-check the pinout of the transformers matches, and if not run with short wires like I did here for the KDMpower PSU:
https://www.badcaps.net/filedata/fetch?id=2058932
.

I'll try to check R31 and maybe replace the transformator since it the pcb layout seems to be almost an 1:1 replica of the LC one. Although not sure when cause I fell for the oldest trick in the book (phishing link that did god knows what to my browser) and I'm trying to find the virus with mbam.....

[kotel studios]

R31 still measures 680ohms in circuit. Transformator doesn't seem to have pass through from primary to secondary side. All pins on both sides show 0.3ohms each to the neighbouring one on both transformators. And ofc the lc one (eel-19-2005) doesn't match secondary side pins with lt419top00....
I also replaced the cloudy diodes (D24 and 16) due to my experience with the tagan but now there's no 5vsb output at all.....

[kotel studios]

Yep, the 5vsb is gone. I have accidentally shorted one of the caps near the middle transformer.... The caps is not shorted (after removing the short) and the dim bulb tester doesn't light up at all (I have checked it with another PSU and it still functions correctly.
Any ideas if this ones just a dud now?

[momaka]

R31 still measures 680ohms in circuit.

That's not right then.
It's OK for a resistor to read lower resistance while in-circuit than it's actual printed value.
Its NOT OK for a resistor to read higher resistance while in-circuit that it's actual printed value.
So that one needs re-checking out of circuit and/or replacing.

Transformator doesn't seem to have pass through from primary to secondary side. All pins on both sides show 0.3ohms each to the neighbouring one on both transformators.

It's not supposed to anyways, so that's normal.
In fact, that's the whole idea of most PSUs: to isolate the primary side from the secondary side so that you don't get shocked.

And ofc the lc one (eel-19-2005) doesn't match secondary side pins with lt419top00....

Make it match... with wires, like I showed in the picture at the end of post # 54.
Just follow where each pin goes on both the eel-19-2005 and the lt419top00 transformers in their respective PSUs / PCBs. For example, on the secondary side there will be 3 pins: one connected to a 1 to 1.5 kOhm resistor and a small diode, and the other two pins each connecting to the Collector terminals of the small TO-92 driver transistors. On the primary, it's typically 5 pins (IIRC): one connecting to the big transformer pin, one connecting to the Collector and Emitter legs of the primary switchers (the 13007's), one connected to primary-side ground (negative on one of the big primary caps) and the other two pins to the bases (through some diodes and a resistor) of the primary switchers. Just trace what goes where and wire the transformer accordingly.

I also replaced the cloudy diodes (D24 and 16) due to my experience with the tagan but now there's no 5vsb output at all.....

None of these are related to the operation of the 5VSB circuit, so you've made a mistake elsewhere. Check you work for solder bridges, bent leads shorting something, and etc. This one is a user mistake, not PSU fault, so check what you're missing.
As a general troubleshooting guide, always check these:
1) Voltage across the primary caps. Both at around 160-165V DC (or 320-340V DC together)?? If yes, go-to 2)
2) Switching device (2N60 MOSFET in this case) and it's Source/Emitter resistor OK? If yes, go-to step 3)
3) Output rectifier OK and nothing shorting the rail (5VSB) to ground?

Yep, the 5vsb is gone. I have accidentally shorted one of the caps near the middle transformer.... The caps is not shorted (after removing the short) and the dim bulb tester doesn't light up at all (I have checked it with another PSU and it still functions correctly.

Which cap(s)?
Looking at the PSU, I can't see the designators on mine, as that's written under the caps, so please provide picture if possible which cap(s) were shorted and how (solder bridge?)

As someone said in another thread, hasten down
i.e. take time to double-check your work, because every time you make a mistake due to doing things too quickly, that introduces a new problem on top of whatever other problem was existing, and that really makes things go much slower in the end.

[kotel studios]

Okay before I go to doing more troubleshooting I soldered on some leads to the primary caps and measured the voltages across them. Turns out there's none at all..... I think I might've killed the diode rectifier but then the light bulb would light up, right?
It also could very well be the switch or me soldering to the wrong spot. I'll go test those theories after the PSU discharges.

[kotel studios]

I have found that the diode rectifier was shorted. What's weird is that I desoldered it and the short on PCB and on itself is... gone?
And since it's an 4 diodes-in-one type rectifier I soldered it back in, checked for shorts in the same spot and powered it on. Was greeted with same results as before... No voltage across primary caps and the bulb stays off.