Dell HP-P2507FWP3

[pdavid]

An Hipro built unit. It went out with lots of smoke. One of the surge protection diode thing blown up, right between the line and neutral of the pfc coil. Really, lots of smoke, like a chimney
I could replace the diode, but will it work? Primary caps are Panasonic 560uF measures 497uf and 504uf. The rest are Ost and Teapo. None of them bulges, but I removed the ones for the to +5vsb.
Any advice what diode should I put there if any?

[PeteS in CA]

Re: Dell HP-P2507FWP3

OK, first off, I don't think that P/S has active PFC. The I/P lytics look like a standard switchable doubler configuration, the labels rates the P/S for dual range AC rather than wide range AC, and the 250W rating suggests late 90s or early 00s vintage (when PFC was still a higher-end feature). If the P/S has a user settable voltage range switch (usually near the inlet) then it is what I think it is.

Your fried part looks like a Metal Oxide Varistor (MOV), and looks like it is on the AC side of the bridge rectifier. Its purpose is to protect the P/S from power voltage spikes. MOVs have three good characteristics and one not so good characteristic. MOVs (1) can absorb a lot of energy, (2) very fast, and (3) are cheap. The not so good characteristic is that MOVs are damaged slightly every time they absorb a voltage spike, which over several years gradually lowers the voltage at which the MOVs begin to conduct. After a time, the MOVs conduct continuously at normal line voltages and self-destruct. If this P/S is of the vintage I suspect, and if it came from an environment with lots of A/C and/or industrial machinery, and/or lots of thunderstorms, that may be what happened to this MOV. OTOH, every electronic component has its limitations, so one massive surge (e.g. a lightning strike in the immediate neighborhood) could have been what fried the MOV.

I think this is what your part is, a V14K300-5 (~3/4 of the way down the page). It's rated for 300VAC/405VDC withstand voltage (guaranteed won't conduct), 470VDC varistor voltage (guaranteed will conduct), 4500A single pulse, 117 joules (energy) single pulse. The voltage rating is the critical parameter; you could use a larger, higher energy, part if it fits.

[pdavid]

Re: Dell HP-P2507FWP3

Thanks for the info about the mov! I'll just try to get the right one from my parts box.
Yeah, there is a voltage range selector, but the wires were too short so I desoldered it when I removed the pcb... the two caps gave it right away huh...
The PSU was manufactured in 2005 july, working til last week. Plenty of connectors, 20/24 mobo, 2 sata, 5 periphelial and one ATX12V. All wires are 18awg.
The place where the psu came from doesn't even have proper grounding. Only that... The electric line is 80 years old in that building, cables are paper insulated in main the breaker box!

More about the psu. It has a sinlge primary switcher, but I can't read the device's name because the pwm module is soldered next to it. I've seen this desing in lot of supplies. I had a 430W Cooler Master psu, it was a Hipro built unit just like this. Pfc coil mounting was the same too. Despite the labeled ratings the secondary side is very generous. 45A and 30A schottkys for 5V and 12V... too bad I can't keep it.

[PeteS in CA]

Re: Dell HP-P2507FWP3

Ah, I missed the big inductor in the third picture. So it has passive PFC. At 250W, a single switch device means it's a forward converter, possibly with a 3842 family current-mode PWM controller. Sounds like a less than pristine AC power environment. The building I work in is about 70 years old and it looks scary - 70 years of building code changes and electricians' hasty habits.

[pdavid]

Re: Dell HP-P2507FWP3

The building I work in is about 70 years old and it looks scary - 70 years of building code changes and electricians' hasty habits.

It doesn't bother me until a touch there a pc case or a radiator... then it zaps me.
So, I got a few orange PVR14D471 varistors. These are 300AC 385DC 4500A rated.
There are 2 more next to the primary caps, they are smaller and look good.

[PeteS in CA]

Re: Dell HP-P2507FWP3

... the two caps gave it right away huh ...

Yeah, I've worked with power supplies and in power electronics since 1980. Three of those years were in tech support with Delta Products.

There are 2 more next to the primary caps, they are smaller and look good.

Those are connected across the big lytics to prevent them from venting during really long surges or if the P/S is set for 115VAC but gets plugged into 230VAC. The MOVs will fry, but after blowing the input fuse. Safety agencies don't want the big lytics venting.

It doesn't bother me until a touch there a pc case or a radiator... then it zaps me.

Sounds like crappy grounding at your building or you have power entries from multiple power grids. Our building mainly looks like @#$%, though a ceiling truss partially gave way a year and a half ago, requiring shutting down an area in the building until it was re-braced. It was eventually figured out that the roof was bearing three times as much weight as it was designed to bear.