LC Power LC380M fan seized. Needs repair

[goodpsusearch]

This is a micro ATX LC Power power supply, not L&C. The label is missing info such as 3.3V & 5V combined power, 12V total output power and total output power. How convenient!

Overall, the psu is not so bad.

There is just 1 common mode coil and no spot on PCB for a thermistor. There are spots for MOV but they are missing.

Input caps are 2x HEC 470uF 200V, their real capacitance is 452uF. The main transformer is ERL-33 and the switching transistors are 2x13009 but in TO-220 package. I would say it is a 250W unit.

5vsb is generated from BH0F70A, this is good.

SG6105D combo PWM and supervisor is used for this half bridge unit.

Toroid coils look good for 250W, 3.3V and 5V use S20C45C schottky rectifier and 12V uses U20C20C ultra-fast rectifier.

I found A928, PNP transistor that failed open. I will attach some pictures of the unit later

[goodpsusearch]

Re: LC Power LC380M fan seized. Needs repair

Pictures after I have removed many caps and heatsinks

[momaka]

Re: LC Power LC380M fan seized. Needs repair

I think your primary transistors are BAD.

PCB area the heatsinks appears a bit toasty. Did the fan seize? Aside from that and the caps, this PSU looks good otherwise. I like how it uses TO-92L transistors rather than regular TO-92. Still, makes you wonder why that one A928 transistor burned. Was it for the fan controller, perhaps?

As for the PSU not having an NTC thermistor: well, it does have a passive PFC choke, so that is usually enough to reduce large current transients from the PSU.

I'm guessing you're going to recap it and use it?

[eccerr0r]

Re: LC Power LC380M fan seized. Needs repair

Yep they're BAD!

Yeah that fried pnp transistor may have been due to the seized fan. It looks pretty close to the fan output and without doing reverse engineering of the tracks it's likely to be what it's for. Hopefully nothing else failed from elevated temperatures (good PSUs should also do a thermal shutdown from cooling failure?)

When I had a PSU that had a seized fan and failed, the output filter toroid overheated and insulation melted down, forcing its replacement. Hopefully nothing this bad happened.

[goodpsusearch]

Re: LC Power LC380M fan seized. Needs repair

Did the fan seize?

Exactly! I added some oil and it came back to life.

Still, makes you wonder why that one A928 transistor burned. Was it for the fan controller, perhaps?

Nope, it has something to do with 3.3V regulation, 1 of its legs is connected to the mag-amp coil, but I can't say for sure.

I'm guessing you're going to recap it and use it?

I repaired it and recapped it. I am giving it back to owner. He wants to build a media player computer for his living room with a micro ATX case he got. Sadly, those micro ATX psus are rare to find and extremely expensive. That's the reason he decided to get it fixed instead of buying a new one.

When I had a PSU that had a seized fan and failed, the output filter toroid overheated and insulation melted down, forcing its replacement. Hopefully nothing this bad happened.

I am actually surprised that the output toroid coil survived.

Well, this is a summary of what I did:

I replaced failed A928 PNP transistor with A1020.

Installed 2 movs. Before soldering them, I covered them with heat-shrink.

Minimum load resistors

Original --> New

3.3V: 47ohm (~0.23W) --> no change

5vsb: something like 1Megaohm --> no change

5V: 47ohm (~0.57W) --> 94ohm, 2x47ohm resistors in series (~0.28W)

12V: 240ohm (~0.62W) --> no change

-12V: 220ohm (~0.67W) --> 240ohm (~0.62W)

-5V: 220ohm (~0.12W) --> no change


Replaced U20C20C ultrafast power rectifier for 12V rectification with STPS20H100CT schottky rectifier

Recap:

2x4.7uF 50V Ltec for the main switching transistors

5vsb: 2x 1000uF 16V Nichicon HD 10mm from Intel motherboard

12V: 1x3300uF 16V Junfu WG 10mm

5v: 2x3300uF 10V Junfu WG 10mm

3.3V: 2x3300uF 10V Junfu WG 10mm

I had trouble fitting 12.5mm Nichicon/Chemicon capacitors in this micro ATX psu. There was just no space available. I have some Panasonic FK 10mm capacitors but I just decided this psu was not worth it, so I used Junfu WG. From my observations, if they are kept cool, they last.

I didn't tweak the fan controller to make the fan more aggressive, because it is already configured to run the fan fast enough (it has to be that way, these micro ATX cases have terrible ventilation). I just made sure that the thermistor is touching the secondary heatsink.

[Behemot]

Re: LC Power LC380M fan seized. Needs repair

There is plenty SFX units on the market, wouldn't that be better option? You can select ones up to Platinum efficiency, that would be about 15 % better.

[goodpsusearch]

Re: LC Power LC380M fan seized. Needs repair

Nope

[momaka]

Re: LC Power LC380M fan seized. Needs repair

Nope

I like that answer, lol .

Forget about efficiency. Just fix the old unit right and be done. I don't want to sound pompous, but I often don't trust manufacturers' work as much as my own work.

Nope, it has something to do with 3.3V regulation, 1 of its legs is connected to the mag-amp coil, but I can't say for sure.

Ah okay. Yes, the 3.3V rail mag-amp circuit does indeed use a transistor (usually PNP-type from what I've seen).

Sadly, those micro ATX psus are rare to find and extremely expensive. That's the reason he decided to get it fixed instead of buying a new one.

Not to mention there is way too much "new" crap out there. Where I used to work, the store sold some micro ATX and a few other non-standard PSUs like that by the brand of Solid Gear. The PSUs didn't look bad internally, but I wouldn't exactly call them "Solid Gear".

I have some Panasonic FK 10mm capacitors but I just decided this psu was not worth it, so I used Junfu WG. From my observations, if they are kept cool, they last.

Maybe their current caps have improved, but I have a PowMax PSU from the early 2000's, and most of its JunFu WG caps either bulged or went out of spec. Funny, because the Fuhjyyu TNR/TMR caps on the 12V rail were just fine right next to them.

So maybe keep an eye on them still. Or at least if the customer comes back and complains, you know what to do.
In cases like this, I usually just "mix-n-match" good cap brands with crappy ones. Typically, I install at least one good Japanese cap on the first spot of each rail, as that is the most stressed spot usually. After that, anything goes.

I didn't tweak the fan controller to make the fan more aggressive, because it is already configured to run the fan fast enough (it has to be that way, these micro ATX cases have terrible ventilation).

Yes, I've noticed that as well. Probably the reason why the PSU fan failed in the first place (was running at higher RPM and got worn out faster). For fans like that, I find that they eventually seize again pretty quickly if not taken fully apart and cleaned very thoroughly (particularly the sleeve bearing - I use a small drill bit for that... but don't rotate it! - push it in-and-out).

[Behemot]

Re: LC Power LC380M fan seized. Needs repair

You can't fix something what's wrong from the beginning. Plus curing it with JunFu(ck)s is not fix anyway.

Modern SFX units are universe better. It almost does not bear comparison - it's like comparing a Trabant to a Rolls limousine.

[momaka]

Re: LC Power LC380M fan seized. Needs repair

Modern SFX units are universe better. It almost does not bear comparison - it's like comparing a Trabant to a Rolls limousine.

That really depends on what's available on your local market, though.

Remember, you live in a different country from goodpsusearch, so you may have different options available. Sure the internet has made it easier to purchase parts nowadays. But again, that also is highly dependent on where you live. If Greece is anything like Romania, Bulgaria, Macedonia, and Serbia, (at least in regards to shopping online), then getting anything shipped from abroad can be a big hassle and make things not worthwhile in the end.

[Behemot]

Re: LC Power LC380M fan seized. Needs repair

Greece is no 3rd world and there is free goods movement in the EUSR. He can easily shop in Germany where they have EVERYTHING.

[momaka]

Re: LC Power LC380M fan seized. Needs repair

Romania and Bulgaria are in EU as well. But shipping from outside the countries is... not so easy/convenient/cheap.

[goodpsusearch]

Re: LC Power LC380M fan seized. Needs repair

And if you need to RMA the item things may get tricky.

[Behemot]

Re: LC Power LC380M fan seized. Needs repair

Not really. After-reseller warranty (that's usually after 2 years here) is usually handled by off-country service centers anyway (well, if you do not live in the country where they have the european service centers anyway lol) so it's pretty much the same. Kinda like with extended warranty for hard-drives or pretty much everything else. Most of these centers are in Germany.

[RJARRRPCGP]

Re: LC Power LC380M fan seized. Needs repair

I think your primary transistors are BAD.

I saw that too, LOL.