Dead Dell power supply

[everell]

Its a Dell...Dude

Its a DEAD Dell power supply with a blinking green LED on the back of the case. She is a Dell 265 watt, DP/N 0053N4, OEM is LightOn. Pushing the small "reset" switch next to the green LED on the back of the case did not help any.

Time for surgery. The LED on the back indicates status of the 5VSB circuit. The "reset" switch next to the LED is not a reset switch, but acts like a PS_on switch, or like shorting the green wire to ground to turn on the power supply. The blinking LED on the back of the power supply indicated that the 5VSB was pulsing.

The 5VSB circuit uses an Infineon ICE 3AR2280JZ-1 chip. I traced the circuit to determine what was there. See attached drawing. Then began preliminary checks for shorts using digital voltmeter. I quickly found that diode D600 coming off the feedback winding of the 5VSB transformer was shorted. This diode is a UG1D 200 volt 1 amp switching diode. Since I didn't have one handy, I substituted a 1N4935 switching diode with similar specs. Applied power and now she works just fine.

So here are some pictures of the power supply. And remember, it's a Dell...Dude

[goodpsusearch]

Re: Dead Dell power supply

Thank you for the pictures and the schematic. Nice you got it fixed!

[PeteS in CA]

Re: Dead Dell power supply

I recommend replacing the 1N4935 fairly soon with a more similar part. The 1N4935 in a 200nS fast recovery rectifier. The UG1D is a 15nS ultrafast. The 1N4935 will run hot and could fail relatively soon. Get a replacement with a reverse recovery time of 25nS or less.

[momaka]

Re: Dead Dell power supply

Nice save, everell!

I also can't praise you enough for the quality of the pictures you upload - top notch, really.

I recommend replacing the 1N4935 fairly soon with a more similar part. The 1N4935 in a 200nS fast recovery rectifier. The UG1D is a 15nS ultrafast. The 1N4935 will run hot and could fail relatively soon. Get a replacement with a reverse recovery time of 25nS or less.

Nah, if that diode was for the primary side aux. winding (aka "feedback" winding), then it shouldn't be a problem at all.

I had a 250 HiPro PSU with a problem like that - shorted diode from the primary side aux. winding that was feeding voltage back to the PWM/FET combo IC. I don't know if the 5VSB was ticking in mine, as the HiPro didn't have an LED indicator for the 5VSB, but the 5VSB was showing less than a volt or so on my multimeter.

So what I did is I replaced that diode like everell and got my PSU running again. If I remember correctly, the original diode was a UF200G (200V reverse voltage, 2 Amps current, 50 ns reverse recovery), but the best I had on hand at the time that I could easily fit in there was an FR153 diode (same 200V reverse voltage, but diode only rated for 1.5 Amps and 150 ns recovery time). Despite knowing that my replacement diode wasn't as good as the equivalent, I read the switching 5VSB IC's datasheet, and it made no mention of what the rating for that diode should have been. Give the amount of current the IC needed from the aux. winding, a 2 Amp diode definitely seemed overkill. So I applied power to the PSU (with a series bulb) and the 5VSB came back working fine. After 30 minutes, I decided to do a real test and plugged the PSU in the wall directly. Then I added a 1 Amp load on the 5VSB (with a 12V halogen lamp), and it worked fine again for a good amount of time without anything overheating. After this, I tested the PSU in a computer and it worked fine too. This was back in 2010-2011 or thereabouts. Ever since then, I've used that PSU in various temporary and permanent PC builds, and it has never skipped a beat. I still have that PSU and still use it for testing unknown hardware all the time. Soon (as in within the next year or so), I may find a computer to put it in again for permanent use. If it hasn't failed until now, I doubt it will fail soon.

... well, maybe not if the output Teapo and Asiacon caps fail (but I may actually recap it).

On that note... those blue Ltec caps in everell's PSU should be recapped on sight. I recently got a big batch of mostly 5-8 year old Dells and HPs, and a lot of them had bad Delta, HiPro, and LiteON PSUs - mostly bad caps looking through the vents, and quite a few of them were these blue Ltecs. So when I see them now, they are "recap on sight".

[Wester547]

Re: Dead Dell power supply

On that note... those blue Ltec caps in everell's PSU should be recapped on sight. I recently got a big batch of mostly 5-8 year old Dells and HPs, and a lot of them had bad Delta, HiPro, and LiteON PSUs - mostly bad caps looking through the vents, and quite a few of them were these blue Ltecs. So when I see them now, they are "recap on sight".

The low impedance, blue and white LTECs are either the LZP, LYZ, or LZG series. I’ve seen tons of LYZ go bad in Acbels, and lots of LZP, LXY (green and white), LZG, and LTG (brown and white) go bad in Lite-on, Hipro/Chicony, and Delta PSUs too.

What’s mystifying about the LZGs is that the ones I see go bad on a regular basis come from PSUs made from 2005-2013, but the ones from PSUs made before (often found in Lite-on or Delta/Newton PSUs made between 2000-2004) almost never fail in my experience (they not only look good but test within spec on the meter). I guess you could chalk that up to inconsistency but at some point, I think LTEC went from bad to worse.

BTW, Hermei/Asiacon and Teapo caps of that age are notorious for going bad without any signs of failure.

That Elite on the primary side may also be par for the course as far as recapping goes (non-Japanese brands do not do well at all as APFC input filtering capacitors).

[momaka]

Re: Dead Dell power supply

The low impedance, blue and white LTECs are either the LZP, LYZ, or LZG series.

LZG, that's the series I was looking for.

But you are right. Looking back at my notes, I also see quite a few of the brown-n-white LTG series were bad. The ones that appeared visually okay were starting to read high capacitance.

And indeed I don't recall seeing that many bad Delta and LiteOn PSUs from the early and mid 2000's as I do from 2007-2008 and afterwards. This last batch completely changed my mind on Ltec. I used to think they were somewhat decent - at least in Delta and LiteON PSUs. But I guess that only applies for the older ones.

In any case, I will take Taicon any day over all other cheap cap brands, with Teapo and OST (RLS and RLG series) perhaps as a close second. Anything below that.... shouldn't be trusted.

That Elite on the primary side may also be par for the course as far as recapping goes (non-Japanese brands do not do well at all as APFC input filtering capacitors).

Good point. I was going to mention that yesterday as well and forgot.

Though I've seen even good Japanese caps fail a lot more often in APFC circuits, so I wonder if APFC just puts too much stress on the caps (in which case, I wonder if adding polypropylene caps in parallel with the main cap will help it any.)

BTW, Hermei/Asiacon and Teapo caps of that age are notorious for going bad without any signs of failure.

Hermei I know are terrible. But Asiacon don't seem to do as bad. Teapo, I rarely see go bad without visual signs, especially SC and SM series.

[Wester547]

Re: Dead Dell power supply

In any case, I will take Taicon any day over all other cheap cap brands, with Teapo and OST (RLS and RLG series) perhaps as a close second. Anything below that.... shouldn't be trusted.

IMHO Teapo is right down there with LTEC or worse. I’ve seen too many Teapo (6.3mm diameter and larger) either bulge in storage (similar to KZG and KZJ) or conveniently outgas the second you apply bias to them to trust any of them.

Taicon had a large rash of bad capacitors too, particularly the 8x11 1000uF 6.3V Taicon HDs found on ASRock motherboards made between 2003-2005 (like this). Those were actually worse than KZG and would very often have a 100% failure rate after 2-3 years. Seen many motherboards with every one blown, even on some NIB boards which were never taken out of their original packaging. OTOH, Nichicon owns 37% of Taicon, so that may say something.

Of course, Nichicon had a bad batch of HM/HN (possibly HD/HZ too... hard to say) in the day as well, so I guess no brand is exempt from failure.

Though I've seen even good Japanese caps fail a lot more often in APFC circuits, so I wonder if APFC just puts too much stress on the caps (in which case, I wonder if adding polypropylene caps in parallel with the main cap will help it any.)

That’s not good. Which Japanese brands and series have you seen fail there? I guess I wouldn’t be surprised to hear that it was NCC - I’ve actually seen an alarming number of 105ºC NCC primaries to go bad, in both APFC and non-APFC PSUs. I haven’t yet figured out if they failed due to overbias or if they’re just from a bad batch.

Hermei I know are terrible. But Asiacon don't seem to do as bad. Teapo, I rarely see go bad without visual signs, especially SC and SM series.

Well, we’ve discussed this before, but Asiacon was just another trademark for Hermei. They are the same caps. Teapo from the early 2000s are actually known to go open without any signs. The ones after, bulge and leak more often.

[momaka]

Re: Dead Dell power supply

Taicon had a large rash of bad capacitors too, particularly the 8x11 1000uF 6.3V Taicon HDs found on ASRock motherboards made between 2003-2005

Taicon on motherboard and Taicon in PSUs is two different things, though. I'm not sure how/why AsRock was the only one to use them. Maybe they got counterfeits? In PSUs, Taicon usually does a bit better than all the rest. *USUALLY*

That’s not good. Which Japanese brands and series have you seen fail there? I guess I wouldn’t be surprised to hear that it was NCC - I’ve actually seen an alarming number of 105ºC NCC primaries to go bad, in both APFC and non-APFC PSUs. I haven’t yet figured out if they failed due to overbias or if they’re just from a bad batch.

Panasonic. Twice now. Two different PSU manufacturers. One was in my ThermalTake M850W PSU I posted about (CWT, PUQ platform). The other was in another PSU back at work. I forgot what manufacturer/platform it was. Might have been an Enermax.

APFC is just crap, though. Get rid of the APFC circuit, and I bet all those problems would be gone. I never even think about recapping the primary caps of regular non-APFC or PPFC PSUs (unless of course, the primary caps were too small... but that's only when you get a cheapo crap PSU on your hands).

Well, we’ve discussed this before, but Asiacon was just another trademark for Hermei. They are the same caps.

Same trademark or not, Asiacon just seem to do better - especially in HiPro PSUs. Perhaps they were "cream of the crop" or better QCed compared to Hermei. But who knows?! That's not to say I trust them, of course.

[Wester547]

Re: Dead Dell power supply

Taicon on motherboard and Taicon in PSUs is two different things, though. I'm not sure how/why AsRock was the only one to use them. Maybe they got counterfeits? In PSUs, Taicon usually does a bit better than all the rest. *USUALLY*

They were found on QDI Pentium 4 motherboards too, and on some old BFG graphics cards. And on some Pentium 4 and Socket A ASUS boards. Certain Netgear network switches, too, such as the FSP7326P POE. I don't think they were counterfeit. What I have noticed is that Taicon's water base series (HD, HF, HI, HH) don't seem to do very well, but their other series (PW, PZ, HW, HG, VT, etc) that use more conventional electrolyte seem to hold up better. I have seen failed Taicon primaries (the AQ series) in LCD monitors and power bricks, though, some of which employed the widerange flyback topology.

Panasonic. Twice now. Two different PSU manufacturers. One was in my ThermalTake M850W PSU I posted about (CWT, PUQ platform). The other was in another PSU back at work. I forgot what manufacturer/platform it was. Might have been an Enermax.

That doesn't seem so bad. When you produce hundreds of millions of capacitors per month, some batches are bound to end up wrong or may go bad altogether.

APFC is just crap, though. Get rid of the APFC circuit, and I bet all those problems would be gone. I never even think about recapping the primary caps of regular non-APFC or PPFC PSUs (unless of course, the primary caps were too small... but that's only when you get a cheapo crap PSU on your hands).

Or if they used a valley-fill PFC circuit. Or if they don't use any bleeder resistors to balance the voltage between the two primary capacitors.

Same trademark or not, Asiacon just seem to do better - especially in HiPro PSUs. Perhaps they were "cream of the crop" or better QCed compared to Hermei. But who knows?! That's not to say I trust them, of course.

Not sure about that. The Asiacon 3300uF 16V and and 3300uF 10V LE capacitors that I pulled from my old Dell Hipro 250W looked pristine but each measured over 10 ohms a piece. Many of the Teapo SC and G-Luxon HM were open too. None were bulging or leaking.

But I hate to hijack this thread any further so we'll just agree that APFC PSUs are asking for trouble regardless of the primary cap brand. For the sake of the PSU Everell posted, I hope nothing else fails.

[drhicom]

Re: Dead Dell power supply

I also have a defective DEll 790 PS DP/N 0GVY79 with a blown C52 cap no value, not enough cap left to read value.