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

[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.
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[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).

[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]

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]

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]

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]

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]

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]

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....