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Old 05-09-2021, 10:28 AM   #1
zunasthegreat
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Default Chieftec GPS-550AB-A (Delta OEM)

Hello again and I really hope somebody can give a heads up so I can find the issue.
This PSU has busted Ltec caps, the 12V and 5VSB ones are sooo bulged and the reading is 28pF... The 5V + 3.3V ones show way above rated capacity and I guess they are approaching their death.

Stock CAPS
12V -> Ltec LTG 2200uf 16V X2 -> Nichicon HV 1500 16V + HD 2200 16V
5V -> Ltec LZG 3300uf 10V -> Nichicon HD 3300uf 10V
3.3V -> Ltec LZG 3300uf 6.3V X2 -> NCC KY 2200uf 10V X2
5VSB -> Ltec LTG 1000uf 10V + 1500uf 10V -> NCC KY 1000uf 16V X2

This patient is from a friend of mine and the system could hung on sleep mode and very rarely would BSOD. After the re-cap I see this strange behavior : doing cold boot the system will 100% of times boot fine run great and all voltages will be fine. The moment I shut down the PC and for about 1-2 minutes the PC will boot fine again! The "magic" happens if I try to boot after 10minutes (the PSU switch is ON but system is shut down) the case FANS will do half a turn the CASE led will start blinking and there will be no power/post from there. It looks to me more like an OCP/OVP or some sort of protection kicking in, from there and the only way to boot is to turn PSU switch off for a while then On again. The 5VSB line looks fine and shows around 5.1V at all times.

*There looks to be a StartUp cap *35V 220uf* that I already tested, removed then re-soldered cause the same thing happened with the replacement cap.
*Most likely a PowerGood signal issue so far but the psu is terrible in terms of repairability.
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Old 05-09-2021, 10:51 AM   #2
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Maybe the caps, when they are discharged, draw too much current to charge up (if they have very low ESR) that the over-current or under-voltage protection kicks in.
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Old 05-09-2021, 12:57 PM   #3
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Went even deeper and replaced ALL caps and found some weird readings. One TAICON 100uf 16V on the board where the FAN connects shows 7.1% vloss on meter and only 70uf, the ESR is 2Ω. The same board on the other side has a cRapxon 10uF that has 8.5Ω ESR and ~6% vloss. The cream of the crop is a 50V 2.2uf ltec near 5VSB with ESR 12Ω ... never seen that high on a cap.

minor caps are

ltec 100uf 25V (on a small board near primary cap) -> NCC KY 100uf 50V
ltec 2.2uf 50V (near 5VSB) -> nichicon PB 2.2uf 50V
taicon 100uf 16V (board with fan + variable resistors?) -> NCC KY 100uf 50V
taicon 22uf 50V (board with fan + variable resistors?) -> suncon 22uf 50V
capxon 10uf 25V (board with fan + variable resistors?) -> suncon 10uf 50V

startup cap and -12V got suncon and KY 470uf

*PG_signal Voltage is ~4.5V

Last edited by zunasthegreat; 05-09-2021 at 01:14 PM..
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Old 05-10-2021, 01:26 AM   #4
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Quote:
Originally Posted by zunasthegreat View Post
The 5V + 3.3V ones show way above rated capacity and I guess they are approaching their death.

Yup, very typical for Ltec caps. If you see them going for past 15% of their rated capacitance, chances are they will continue increasing and eventually pop... and it's just bad luck to leave Ltec caps in a PSU.

Quote:
Originally Posted by zunasthegreat View Post
Stock CAPS
12V -> Ltec LTG 2200uf 16V X2 -> Nichicon HV 1500 16V + HD 2200 16V
5V -> Ltec LZG 3300uf 10V -> Nichicon HD 3300uf 10V
3.3V -> Ltec LZG 3300uf 6.3V X2 -> NCC KY 2200uf 10V X2
5VSB -> Ltec LTG 1000uf 10V + 1500uf 10V -> NCC KY 1000uf 16V X2
Looks good. Nichicon HD and UCC KY is pretty close to specs for Ltec LZG and LTG series, so I don't think those are the issue.

Quote:
Originally Posted by zunasthegreat View Post
After the re-cap I see this strange behavior : doing cold boot the system will 100% of times boot fine run great and all voltages will be fine. The moment I shut down the PC and for about 1-2 minutes the PC will boot fine again! The "magic" happens if I try to boot after 10minutes (the PSU switch is ON but system is shut down) the case FANS will do half a turn the CASE led will start blinking and there will be no power/post from there. It looks to me more like an OCP/OVP or some sort of protection kicking in, from there and the only way to boot is to turn PSU switch off for a while then On again. The 5VSB line looks fine and shows around 5.1V at all times.
Can you confirm if this happens with another PSU? Just want to rule out this isn't caused by the motherboard or other component. I have not seen an issue like this with a PSU before.

If it was a cap issue, the PSU should have a problem booting up when cold, but not when hot. Perhaps also inspect all solder joints and especially anything soldered to the heatsinks, as that could have cracked.

Also, does the PSU have one single 400/420/450V cap or two 200V ones? If it's the former, the PSU has APFC circuit, and those do like to "eat" primary caps sometimes. Pull it out and check that it's capacity and ESR are normal on your meter.

Apart from that, not sure what else to check. Have anymore pictures of the rest of the PSU?

Quote:
Originally Posted by zunasthegreat View Post
Went even deeper and replaced ALL caps and found some weird readings. One TAICON 100uf 16V on the board where the FAN connects shows 7.1% vloss on meter and only 70uf, the ESR is 2Ω. The same board on the other side has a cRapxon 10uF that has 8.5Ω ESR and ~6% vloss. The cream of the crop is a 50V 2.2uf ltec near 5VSB with ESR 12Ω ... never seen that high on a cap.
Yeah, looks like even your small caps are starting to fail - or at least the one with 12 Ohms ESR. Otherwise, for small 5x11 mm caps, up to 2-3 Ohms ESR is not necessarily bad. It all depends on room temperature, too. When cold below 20C, some of these caps may measure even higher. But generally, when I see them go much above 3-5 Ohms, that's when I usually elect to replace them (and I always try to anyways, unless I'm low on replacements.) Should note, though, that even most of my new Nichicon and Rubycon caps in the 1-10 uF range regularly measure 0.5 to 1.5 Ohms ESR when new.

Quote:
Originally Posted by zunasthegreat View Post
startup cap and -12V got suncon and KY 470uf
Check how the -12V rail is generated. If there is a 7912 3-terminal regulator, make sure the caps on the regulator input and output are both good.

PG at 4.5V sounds normal.
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Old 05-10-2021, 03:01 AM   #5
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Same behavior with another board, can't say for sure if the psu had this behavior pre-cap. I'm pretty impressed that it worked like that with dead 5VSB and 12V caps. It uses one 450V samxon primary cap and has APFC like you said. I replaced all small caps and now it does turn on with better consistency. -12V rail looks good and give around -12.05V but still can't find out why cold boot works and "hot" boot fails. I'll provide more photos when I remove 450V cap for checking.

photo from another site/user

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Old 05-10-2021, 05:05 AM   #6
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Samxon 450V 330uf primary cap is ~305uf on the meter, looks pretty good. Can it really be the 5VSB caps ?

*On the board with variable resistors the last one can alter the +5V/+12V voltages, pretty cool cause of group regulated design.
*Had done a pretty bad decision : Next to the +12V filter caps was the 1500uf 10V failed ltec, I've put there a nichicon HM 1000uf 10V (guess thats a super low ESR) Looking at the datasheet and under the PCB its now clear that the cap there was the second one for +5V filtering ... I'll just swap it for a GP cap or something like NCC KY.
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File Type: jpg IMG_20210510_131526.jpg (611.3 KB, 20 views)
File Type: jpg IMG_20210510_120953.jpg (794.6 KB, 20 views)

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Old 05-10-2021, 10:40 AM   #7
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Quote:
Originally Posted by momaka View Post


Check how the -12V rail is generated. If there is a 7912 3-terminal regulator, make sure the caps on the regulator input and output are both good.
Yes its a 7912 and I replaced both caps there, a 2.2uf and the 470uf.
I'm testing +5V line now with a VY 1000uf 16V in the place of that HM cap.
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Old 05-11-2021, 01:41 PM   #8
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

I just removed some of the low esr caps and the "hot" boot issue is fixed so far.

+12V has now a Lelon RGA 3300uf 16V & nichicon HV 1500uf 16V
+5V has nichicon HD 3300uf 10v & nichicon VY 1000uf 16V
+3.3V Still has the same 2X KY 2200uf 10V (I've some Panasonic FJ's 3300uf 6.3V that I'm willing to try)
+5VSB Still 2X KY 1000uf 16V
-12V Nichicon PB 2.2uf & KY 470uf

The only working and in-spec caps are the Primary 330uf 450V samxon and an NCC KY 1000uf on the +5VSB, that cap is likely the reason that the PSU could boot. The 2 caps that fixed the PSU is the removal of the +5V nichicon or the HM 1000uf or the +12V HD 2200uf 16V.

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Old 05-14-2021, 04:16 PM   #9
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Quote:
Originally Posted by zunasthegreat View Post
I just removed some of the low esr caps and the "hot" boot issue is fixed so far.
Interesting.
This is a "newer" Delta design with -52 core material on the main output inductor, so it shouldn't have had problems with very low ESR caps. Granted Nichicon HM is probably a little too far too low, and HV might be just on the edge of acceptable. But HD and UCC KY should be absolutely fine. If that's not the case, keep an eye on this unit, as I suspect there may be something else going on (though not sure what exactly at this point.)
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Old 05-14-2021, 10:05 PM   #10
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Quote:
Originally Posted by momaka View Post
Interesting.
This is a "newer" Delta design with -52 core material on the main output inductor, so it shouldn't have had problems with very low ESR caps. Granted Nichicon HM is probably a little too far too low, and HV might be just on the edge of acceptable. But HD and UCC KY should be absolutely fine. If that's not the case, keep an eye on this unit, as I suspect there may be something else going on (though not sure what exactly at this point.)
I think some other key component might gone out of spec too, the +12V caps had no juice left at all. Another strange fact now is that the user said at some point that he had 2 HDD's gone bad. Could be the ripple from the +12Voltage? or just bad luck ... who knows. Any thoughts on trying 3300uf FJ's 6.3V for 3.3V line ? Other option is GP Nichicon VZ 3300uf 6.3V (105 C) or Lelon RGA GP 3300uf 6.3V (cap has to be 10mm in diameter). Not many UCC KY 2200uf left and are really hard to find so I'm willing to try those instead.

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Old 05-15-2021, 02:11 AM   #11
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

I think Panny FJ should work for the 3.3V rail, since it's a mag-amp, and those usually do OK with lower ESR as well. I don't remember where FJ was in terms of specs... but likely lower ESR than FR or FM... so maybe around Nichicon HM spec? All I can tell you is that I've used FM on a few Delta PSUs, and they've been OK, so FJ shouldn't be too much of a change. I've also used a lot of Rubycon ZLH, which I think are similar to FM/FR, if not lower ESR, and those have worked OK too. But if not, the VZ is a pretty safe bet. It may not filter ripple as well, due to being GP and not having very low ESR, but at least there is never any danger of oscillations with VZ.
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Old 05-15-2021, 03:13 AM   #12
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Thanks for all the knowledge and help very much appreciated. Btw checking reviews I see expensive PSU units with really underperforming caps. Review example is a ~120$ 650W Gold PSU with Teapo SC caps ...
Maybe global situation affect OEM's too but the price is very high for that kind of passive quality components.

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Old 05-16-2021, 11:17 AM   #13
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

I tried FJ 3300uf 6.3V on that Delta made 550AB and it works fine so far. The interesting part is that I also tried two of those caps on my APS-550S (different OEM) and it could start. It made a bizzare hiss sound and then switched off from OVP/OCP I guess. Upon going back to 2X NCC KY 2200uf 10V the PSU works fine.

From the schematic the mag amp is the L301 right ?
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Old 05-16-2021, 07:45 PM   #14
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Quote:
Originally Posted by zunasthegreat View Post
From the schematic the mag amp is the L301 right ?
Correct.

Though, I'm not sure why the mag-amp coil (L301) on that schematic is connected *after* the 5V rail rectifier (D301/D302). Perhaps a mistake in the diagram? For most PSUs I've seen, it's always been connected *before* the 5V rectifier - i.e. same tap as the 5V rail, but before its rectifier.

Also, if that APS-550 is anywhere near a modern unit (which it looks like it is with APFC and whatnot), I'd be surprised if the 12V rail tap on the transformer really was connected like drawn in the schematic. Normally, on newer group-regulated PSUs, the 12V rail is usually just a 7V rail super-imposed on top of the rectified 5V rail. Thus, any current draw on the 12V rail also passes through the 5V rail's rectifier to create a bigger drop on the 5V rail, so that the 5V rail regulation is better.

Quote:
Originally Posted by zunasthegreat View Post
Btw checking reviews I see expensive PSU units with really underperforming caps. Review example is a ~120$ 650W Gold PSU with Teapo SC caps ...
Maybe global situation affect OEM's too but the price is very high for that kind of passive quality components.
I doubt it has to do with the global component supplies.
Main problem is people still focus more on features and efficiency than they do on the caps. And yet caps are still one of the main reasons why otherwise well-built PSUs like these still end up bad - be it bad caps on the output filter or the main / APFC filter caps. At least the above-mentioned unit has decent total capacitance on the input. A lot of the older (and cheaper models) PSUs would try to get away with about half of that... and those are the PSUs that seemed to have "paid the price", IME (i.e. blown input cap or caps.)

Last edited by momaka; 05-16-2021 at 07:48 PM..
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Old 05-17-2021, 05:33 AM   #15
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Yeap mag amp has different drawing on the GPS model. Probably user drawn error.
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Old 05-29-2021, 09:05 AM   #16
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Another prospect that needs care

This gutless Force 450W was 9.99 5 years ago, worked for like 30minutes in total. The owner said this glorious unit would not make it into windows or would bsod randomly (pc was HD 5770 + am3 athlonII). I opened it up and saw the ugly green Y-brand caps and the infamous double diode treatment for the +12V. Plus thin cables an 80mm junk fan and 1mm heatsink, transformer says ERL-35 but stickers do deceive. Anodia 200uf 200V primary caps and many many 47uf caps around that 2005 chip.
After 5years on the shelf the caps have already show raised capacity (1000uf each rail). I've replaced them with 3300uf and even removed that double diode with an MBR20200CT. With a jumpstart wire and 2 dvd-roms for load the +12V shows 12.8V on the multimeter ! Upon checking again while connected to a c2q s775 mainboard it now barely hits ~12.5V. 3.3V (3.37V) and 5V (5.05V) look good. Any tips for load resistors or I should not bother at all ?
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Old 05-29-2021, 05:32 PM   #17
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Please be sure to replace those two blue ceramic caps in the top left of the first picture with real Y caps. It's a safety issue.

Those 220uF primary caps might be OK for 150W, but for much higher power the 50 Hz ripple will get high and your hold up time with a power drop-out won't (hold up). With all the other factors that probably make 200W-250W the realistic power capability of the thing, I'd suggest replacing those 220uF caps with 470uF caps.

If the input bridge rectifier is actually four discrete rectifiers and you have a decent bridge rectifier in your spare parts bin or a power supply you are parting out, a higher current "real" bridge rectifier would be nice.

It'll never do 450W without a dramatic event, and 300W would be pushing your luck. But it's something to learn on.
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Old 05-29-2021, 08:17 PM   #18
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Quote:
Originally Posted by zunasthegreat View Post
This gutless Force 450W was 9.99€ 5 years ago, worked for like 30minutes in total. The owner said this glorious unit would not make it into windows or would bsod randomly (pc was HD 5770 + am3 athlonII).

With those diodes-on-a-bracket (DOAB), I'm surprised they didn't short-circuit from an overload right away when he hit the power button. HD5770 alone is about 100 Watts TDP. Athlon II (assuming X2 and not the more power-hungry X3 or X4 ) is probably another 70 Watts. Granted that HD5770 probably never managed to pull its full-rated power, as the system didn't seem to be stable enough to allow your friend to try any games or 3D load. But nevertheless, the Athlon II (X2?) CPU with the HD5770 idling was probably around 100 Watts mark... and I'm not surprised the system crashed at all. The original single 1000 uF caps will probably be able to filter no more than 2-3 Amps of current draw from each rail before ripple goes way out of spec.

Quote:
Originally Posted by zunasthegreat View Post
Any tips for load resistors or I should not bother at all ?
Oh gosh, were do I even begin (or end) with this PSU?!
As much as I still fix worthless old crappy PSUs, even this one would be hard to justify on my list.

Changing the load resistors probably won't do anything for the voltage regulation on this PSU (but removing/changing/re-arranging them so that they don't cook your caps if anything dissipates more than 0.5 Watts in there might be a sound idea.) Voltages are/were way off because the "manufacturer" (child locked in some garage, probably) anticipated the 12V rail would see a large forward voltage drop from the crappy DOAB contraption, so they probably wound an extra turn or two on the main transformer for the 12V rail to try to correct for that. So when you switched to the MBR20200CT, that significantly reduced the voltage drop and hence got a much higher 12V rail. I suppose that would be OK if this PSU is used only on a 12V-based PC... but I just feel very uneasy with the entire (lack of) build quality of the unit. The small output toroid and single output cap per rail setup will yield absolutely craptastic ripple and noise on the outputs, no matter how much you upgraded the capacity. Even if the PC boots, you can bet all of the system components will be stressed with extra ripple. Any mechanical HDDs will probably be the first to bite the dust from that. This PSU *might be* (I use that term very generously here ) just OK for something like a Pentium G or Athlon II X2, but *without* any sort of discrete GPU - i.e. keep system power draw under 60-70W total under load. PeteS suggested the unit can do 150-200W... and indeed it might on the primary side and with your upgraded rectifiers. But I don't want to even imagine what the output ripple will look like then. Also, there's a good chance the 12V/5V main output toroid will burn out quickly overtime with anything higher than 80-90W draw. Colors indicate it supposedly uses -52 core material... but I suspect that may not be true Micrometals core and probably some cheap Chinese variant of it, given the rest of the components. So I won't hold my breath to see if it will perform well.

Also, those heatsinks look anemic. The fan will need to push a lot of air to keep things from overheating... but then I suspect the fan will fail first in a year or two and take the entire PSU with it. I'm guessing it's wired directly to 12V right now? If so, 1-3 years is about the right time for these cheap fans to seize up (especially with 8h/day operation, or evenmoreso if running 24/7.)

Lastly, I see the you put a thermal pad for the 12V rectifier but no insulating nut on the screw. That means the secondary heatsink is connected to 12V output... which is how it was before, as we can see the two Cathodes on the DOAB rectifier connect to the heatsink. That said, if you have cheap ceramic thermal compound, you can use that instead of the silicon thermal pad for slightly better heat transfer to the heatsink. But TBH, I don't think that's going to save this PSU. Just mentioning this as an alternative, in case you wanted to save an extra thermal pad for future projects.

All that aside, I do congratulate you for putting that much effort for keeping cheap Chinese junk out of landfills. The PSU may still not be good, but it's a mile better than it was before.

Quote:
Originally Posted by zunasthegreat View Post
Another prospect that needs care
You mean ?

Quote:
Originally Posted by PeteS in CA View Post
It'll never do 450W without a dramatic event, and 300W would be pushing your luck. But it's something to learn on.
Honestly, I think even 150 Watts would be pushing the luck on this thing... and that's with the upgraded caps. And moreso, I don't think the PSU will last long with such a load. Maybe a year, maybe less. Ripple-wise, I bet it would fail at over 100-120W, even with the upgraded caps.

Really this PSU should just be scrapped for spare parts. Now when you collect about 5-6 of these gutless PSUs, you might have saved just enough parts to build one semi-decent 200W unit... MAYBE!

Oh, and did that thing really cost €10??! Holy crap, what a ripoff!!! You can get used quality OEM PSUs for the same price. Now if it was "free" with the case, I probably wouldn't protest the free parts and cables for my spare junk parts bin. But anything over even €2? Nah, forget it.

Last edited by momaka; 05-29-2021 at 08:36 PM..
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Old 05-30-2021, 01:57 PM   #19
zunasthegreat
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Original owner paid 9.99€ 5y ago, he gave it for free for further testing. He also said some quality comments back then based on the fact that he had to use onboard GPU to boot with this gem "450W" sticker PSU.

Its wired on 12V as you said and the FAN "looks" utter crap but I have another junk casing with 120mm fan that I can use. I did some open case thermal check with : Phenom II X4 3 GHz / HD 5450 / 1x HDD and had OK-ish temps. With room temp around 27 C I had 41-46 C around filter caps, 55-60 C near the heatsink with the SBR's and the 3.3V coil, rest was around ~40 C. Dunno if the weak 3.3V/5V makes it suitable to power the retro P4 s478 / 9600XT system I have for Win98/DOS/WinXP.

I tried mounting the SBR like you suggested with a plastic washer and it was funny ... upon starting up all voltages were fine but the PSU made a horribly high pitch sound. Now again without the washer the strange sound is gone. Other 2 SBR's have that plastic washer only the +12V diode was without one.

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Old 05-30-2021, 11:16 PM   #20
momaka
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Default Re: Chieftec GPS-550AB-A (Delta OEM)

Quote:
Originally Posted by zunasthegreat View Post
Original owner paid 9.99 5y ago, he gave it for free for further testing. He also said some quality comments back then based on the fact that he had to use onboard GPU to boot with this gem "450W" sticker PSU.
LOL.
Ripple must have been through the roof even with the original caps new back then, just as I suspected. Reminds me of the problems I had with a cheap Deer/L&C PSU many years ago making a PC of mine (at the time) crash like mad with any significant CPU + GPU load. Actually, this was the PSU:
https://www.badcaps.net/forum/showth...302#post224302

Quote:
Originally Posted by zunasthegreat View Post
Its wired on 12V as you said and the FAN "looks" utter crap...
With room temp around 27 C I had 41-46 C around filter caps, 55-60 C near the heatsink with the SBR's and the 3.3V coil, rest was around ~40 C.
Those temperatures aren't too terrible indeed... but considering that's with the fan going on full blast, just imagine what would happen when it starts slowing down due to bearing wear and it starting to seize up.

BTW, I got more or less the same temperatures on an old half-bridge PSU when stress-tested to 144 Watts of load on the 12V rail (and about 170 Watts total.) The PSU didn't have impressive heatsinks either, but they were better than the one on this unit. And the fan was temperature-controlled and only running on about 7-8V with that load. So the PSU had considerable headroom to do a little more.

Quote:
Originally Posted by zunasthegreat View Post
Dunno if the weak 3.3V/5V makes it suitable to power the retro P4 s478 / 9600XT system I have for Win98/DOS/WinXP.
Yeah, I wouldn't try it with that PC if the CPU is powered from 5V and not from 12V.
Given how high the 12V rail is already, a heavy 5V load would push it further up and very likely far out of spec. Also, high current draw on the 5V rail means you'll need a lot of output filter caps on the PSU to be able to handle the ripple. So most likely the ripple will be quite bad, even with the upgraded caps already in there. The 12V rail needs to provide less current for the same power draw (due to higher voltage), so you're likely to see less ripple current and noise on the outputs too.

Quote:
Originally Posted by zunasthegreat View Post
I tried mounting the SBR like you suggested with a plastic washer and it was funny ... upon starting up all voltages were fine but the PSU made a horribly high pitch sound. Now again without the washer the strange sound is gone.
Unless the heatsink is connecting other components to the 12V rail, there should be no reason why this is happening.
The tab on these rectifiers is tied to the common Cathode of the internal diodes. So no insulating washer = heatsink connected to whatever rail doesn't have a rectifier with an insulating washer (in this case, the 12V rail.) If you remove the insulating washers on the other rectifiers (3.3V and 5V rails), then you will have the 5V and 3.3V shorted with the 12V rail.
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