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

[kotel studios]

Okay it was another 230v cable connecting to the board doing all this wonky stuff. With it replaced the PSU runs stabely enough. No funky smells or anything.
Secondary heatsinks get around 54C warm after running with 5 3.5" HDD's and an mainboard without CPU connector in place and an 12v 35W bulb on 5v/12v rails for around 10-20 minutes.

I guess this is another repair finalized without the optional compaq PSU which shocked me wit an bright white arc from it.

Many thanks to momaka for helping me out here and прямо for sending me an generic 2002/2003 PWM IC PSU schematic.


But still, how did the PSU repair itself? It will be another unsolved retro mysteries again....

[kotel studios]

Okay and more weird stuff.
Now after putting the sec aux rail diode back in the PSU can start with the original rail? Although there's an weird high pitch sound coming from somewhere primary to transformator side. And it's not the fan (I have unplugged it for funky smell testing).
[s]Maybe the BJT's burning? I don't have any more left of them so I don't wanna risk burning my last working pair out....[/s]
Turns out it was the 3.3v buck converter coil. Redone the solder on it and the smaller coil near it on the 3.3v rail and the noise is gone and the PSU never died so far from my testing.
Can this be that the 3.3v rail had lose solder and was keeping the PSU from starting all along? But I did get 3.3v on the correct pin on the PWM IC before... This doesn't make any sense. sec aux rail is still 16.41v.

[kotel studios]

Huh, this is weird....
So I redone the same test again and no wonky stuff. I have upped the voltage to 3v and I only heard the relay sound. And since I didn't have anything left to lose I upped it to 4v and spam-shorted the PS_ON (with the relay sounds). And guess what?
It works. 5V rail is generating proper (5.04v). Weird how when I turned off the power to the sec aux rail (my bench PSU) the excellent was still running (4v reading from my MM)...
Anybody that could tell me what the hell is happening here?

EDIT: I was dumb and I was shorting the PS_ON like it was an PC button
It now turns on fine when injecting 4 and even 5v. I guess next step is to figure out why the sec aux rail is doing wonky voltage generation.

[kotel studios]

So I found something weird out. When I desoldered the anode of the sec aux rail coming from the transformator I now see 1.7V on the rail. I also hear some weird sizzling noise which sometimes appears and a funny smell follows. There wasn't anything shorted.

Now I am more keen on transferring over the parts from this to the LC PSU board. In fact I might actually start the transfer today.
As for the destructive test I think it's better to leave as a last resort if the frankenstein excellent power/LC PSU won't work.

[kotel studios]

I have done measurement error. I have accidentally put the probe at 5VSB anode, not sec aux rail cathode....
I get 16.41V in the correct spot I think that is way too high.... Might be wrong since the all the lythic craps were changed. But nontheless other components might be screwed, but still, above 16V to drive the primary BJT's is too much IMO. I'll try to cut the power to sec aux rail and inject voltages starting from 7V to 9V (emmiter-base max voltage) and if that doesn't help up to 12 or 14v.

[kotel studios]

Okay so I have risked seeing the diodes go sparky spark and applied power to the PSU (with the bulb protection). And it's back to the half-dead state....
I guess we could only drive the primary side with one from another PSU

Or we could go the screwery way with success chances bellow 50% and put the excellent power parts into the LC board and hope nothing else was screwed, which now it seems there is something badly screwed.....

On further inspection I see there's only 1.7V on the sec aux rail (at least that's what I think it is cause the other two pins connect to GND and an big diode on the 5VSB).... From the knowledge of the FSP repair I know that two transistor 5VSB PSU's run on 10-14V. Although, the primary BJT's are E13007's and I think they're driving voltage should be 9V or around that....
Weird how I get nothing when I use the 20V range (2V range shows proper reading, 20V range reads nothing).
And the "relay" noise I get while shorting PS_ON isn't from the fan, but somewhere from primary/transformator arena.

[kotel studios]

The probable cause for no life here was an broken neutral cable going from the switch to the board.
Although before I go and power it on I must know what specs are the D24 and D16 zener's cause they had no markings and I have replaced them with 4148 signal diodes, which probably could work?

[kotel studios]

Check the fuse and NTC thermistor on the input. If these are good, you have a wiring error somewhere... or user error (multimeter not connected properly or on the wrong setting)... or?? At this point, only you can find out, unless one of us has a chance to teleport and look over your shoulder to see what's happening.
.

Fuse is good and NTC thermistor is also good (6.8ohms out of circuit). The Y and X safety caps also measure their capacitance, although I don't ready any resistance on them.
As for the diode rectifier it wasn't ever shorted. I just confused two pins with the ones from the filter transformator (or whatever it is).

[momaka]

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.

Check the fuse and NTC thermistor on the input. If these are good, you have a wiring error somewhere... or user error (multimeter not connected properly or on the wrong setting)... or?? At this point, only you can find out, unless one of us has a chance to teleport and look over your shoulder to see what's happening.
.

[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.

[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.

[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]

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?

[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]

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.....

[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]

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.

[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]

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.

[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.