Generic PSU 400W

[Behemot]

Re: Generic PSU 400W

After a couple of minutes, the 5V and 12V wire cables became hot all their lengths outside of the PSU casing.

Thats it. If it was conducting heat, there would be temperature gradient. The resistor simply does not have enough power dissipation to heat several long wires to almost same temperature all along. Have you ever tried to heat 1 meter long copper pipe with open flame? It will barelly get warm on the other end when one end is shining red.

You know what, desolder the resistors and try again. Than share the results.

[kc8adu]

Re: Generic PSU 400W

better cover that thing up before the flies blow it.
i tossed one like it last week.when our shop help kid held it up and said this is a really well built unit laughing i told him to throw it out.its not worth the battery discharge on the screwdriver to open it and laugh again!

[UserXP]

Re: Generic PSU 400W

Not that much. I don't believe it being able to conduct heat over tiny wires at some 20+ cm lenght.

Usually +5 and +12 V are most used voltages, +3,3 V is barely used these days so there is no power output thus no reason for wires to heat up.

Hi again, guys. I do not wish to sound like I'm contradicting or anything like that, but it's the truth. Only 5V and the 12V wires are getting hot. Because of the resistor which becomes burning hot. If at some point it got hot enough to desolder itself and the wire next to it, then the temperatures it reached were surely at least 200 degrees or more. Some of that heat ought to have passed through the wires and then towards the socket.
In order to rule out that the motherboard itself is causing this, I started the PSU with nothing connected to it, only by using a single piece of wire between the green pin and the ground pin. After a couple of minutes, the 5V and 12V wire cables became hot all their lengths outside of the PSU casing.

I saw several pictures of some scorched pins on 20-pin sockets on the motherboards. I am guessing that malfunctioning PSUs like this one, if connected to the board for a sufficient period of time, may actually do that kind of damage.
Everything I described above is exactly as is. Look at the picture: the resistor gets burning hot, and first it desoldered itself (1), during that process it desoldered one 5V wire (2), and 12V wire(3). Then the heat probably gets transfered to other red and yellow wires soldered to the same place on the PCB. Those wires then become hot all their lengths outside the PSU's casing.
Somebody here suggested me to throw this PSU into a fire before it lays eggs, I guess I'll have to do just that. It looks like this PSU is on a good way to throw itslef into a fire of its own.

[c_hegge]

Re: Generic PSU 400W

Agreed. Wires don't conduct heat that well.

[Behemot]

Re: Generic PSU 400W

Yes, guys, I am sure. I am telling you, that is exactly what happens. The red wires, which transfer 5V, are connected at one solder point with the problematic resistor. As you know, PCB leads and wires are made of copper, which is an excellent heat conductor.

Not that much. I don't believe it being able to conduct heat over tiny wires at some 20+ cm lenght.

Usually +5 and +12 V are most used voltages, +3,3 V is barely used these days so there is no power output thus no reason for wires to heat up.

[everell]

Re: Generic PSU 400W

You need to trade that thing for a good ole Bestec ATX-250 12E!

[UserXP]

Re: Generic PSU 400W

Yes, guys, I am sure. I am telling you, that is exactly what happens. The red wires, which transfer 5V, are connected at one solder point with the problematic resistor. As you know, PCB leads and wires are made of copper, which is an excellent heat conductor. Only the red and yellow (12V) wires get very hot (because of the contact with the overheating resistor - anyway, you can see on the above pictures that the insulation on some of those wires got burnt), but since they go all the way to the motherboard 20-pin connector, when this PSU is connected with a good working board for no more than 5 minutes - you can actually fill the hot wire(s) by gripping the cable bundle that goes to the 20-pin connector, pluged in its socket on the MB. Then the area around that socket on the MB starts to get pretty hot. Since 5V and 12V wires are hot, their respective pins on connector and MB become hot as well (because heat gets transfered on them through the wires). The MB is fully functional, and when tested with other PSU it does not heat up there. I guess this PSU transfers both power and a bit more heat through the wires... and that's scary.

[mariushm]

Re: Generic PSU 400W

Heat wouldn't go up the wire.

I'd bet on the metal in the connector being too loose, making an imperfect connection to the motherboard.

[Behemot]

Re: Generic PSU 400W

You sure? Stranded wire usually does not conduct heat so well.

I would more bet on several things, connected with each other

- too thin wires, making huge losses
- conencted with ^, lower voltage making board suck more current, even worse losses on wires
- el' cheapo pins on connector, making transitional losses

Low voltage on +5 V only confirms it. This PSU seems to be utter crap…the resistor maybe even baked itself to lower resistance, it may be sucking much more current than supposed to.

[UserXP]

Re: Generic PSU 400W

Yes, this one will definitively be stripped off of usable parts and then trashed. The overheating resistor problem becomes more than that. After testing for awhile, I found that the heat it produces actually gets conducted through the solder and lead points, and then through the wires connected to it - and some of those go to the MB connector, which makes the MB socket very hot. I suppose if left longer on, its plastic will eventually get melted, exposing the contacts and maybe burn itself or the motherboard PCB. Which is out of the question, we'll all agree.
Also, the problematic 5V output (having connections with these overheating resistors) is only 4.3V. Not good enough.

[goodpsusearch]

Re: Generic PSU 400W

Already done that. The fan was spining very easily already, but I took it apart, cleaned it nicely and lubricated the axle a bit - now it spins even more easily and quiter. I'm sure it will come handy in some part of the PC casing.
I guess I'll have to part from the idea of fixing this PSU, though I really wanted to try. But if it will not work safely, then there's no point I guess.
Anyway, I'd like to everyone of you who took the time to read my posts and give all these nice advices.

You can easily find better power supplies that actually worth a recap/mod.

[UserXP]

Re: Generic PSU 400W

Already done that. The fan was spining very easily already, but I took it apart, cleaned it nicely and lubricated the axle a bit - now it spins even more easily and quiter. I'm sure it will come handy in some part of the PC casing.
I guess I'll have to part from the idea of fixing this PSU, though I really wanted to try. But if it will not work safely, then there's no point I guess.
Anyway, I'd like to everyone of you who took the time to read my posts and give all these nice advices.

[Pentium4]

Re: Generic PSU 400W

Better safe than sorry - disassemble it anyway and lubricate if needed. It's never nice when it seizes

Yes. That's what killed the one I had, the fan seized up stiff as a board, and it wasn't quiet when it was working

Thanks, everyone. After all the above said, I am surprised it lasted these 6 years or so.
I can not measure the outputs because I do not have the appropriate equipement to do that, but even if it tops 250W, I will not use it. That would be just too weak and hazardous for motherboard and GPUs...

I doubt the ripple is in spec even at 75W!

[UserXP]

Re: Generic PSU 400W

Thanks, everyone. After all the above said, I am surprised it lasted these 6 years or so.
I can not measure the outputs because I do not have the appropriate equipement to do that, but even if it tops 250W, I will not use it. That would be just too weak and hazardous for motherboard and GPUs...

[Behemot]

Re: Generic PSU 400W

Better safe than sorry - disassemble it anyway and lubricate if needed. It's never nice when it seizes

[UserXP]

Re: Generic PSU 400W

Well, if the repairs bring more risks and investments than the actual gain, then usable parts will come in hand. The fan is surpisingly quiet and is still working well, even with its age. :-/

[mariushm]

Re: Generic PSU 400W

I know the model, it's like one of my old power supplies, only that one was LC-B450..

Yes, insufficient solder on the bottom where the cables are.
The amount of solder should be like on the orange and black cables, maybe even a bit more.

Transformer is actually ERL-33 , not ERL-35. If you desolder it completely, you'll probably find a label saying ERL-33 on its bottom. There's also the pcb holes for ERL-35 right near the heatsink.

It's good for about 150-200w like I said, could do a bit better with inductors and capacitors in the missing locations.

That resistor on the 4th picture.. almost looks like a bad solder join, but with lead free solder you never know...

[Behemot]

Re: Generic PSU 400W

No, this one is doomed from the very moment they even drawed it's schematics.

I suggest taking usable components from it and getting something more of a power supply than reduction from 230 V AC to low DC voltage to play with.

[Pentium4]

Re: Generic PSU 400W

I had the same exact L&C PSU except rebranded under "Nift"....The worst part of the thing is the amount of secondary filtering...where are all the caps?!?! Pretty sure it has a 30A schottky for 5V though, that part is worth keeping

[UserXP]

Re: Generic PSU 400W

OK, guys, here are some additional photos of this PSU. You can see its full label now. Also, you can see the whole PCB (I cleared the dust so it can be viewed better), and the problematic resistor also. I don't see any burn marks on the solder side, just on the other side. Today I also noticed that one +12V yellow wire which is closest to the burning resistor also got unsoldered, so I soldered it back again (it is the first pin down and right of the resistor, on the close-up picture).
I am a bit scared now to continue fixing this PSU because it obviously gets so hot in there that there's no way to know what else is going to overheat and unsolder. Unless there is a certain fix...