Epower EP-600NE-XV Shuts down intermittently

[Pentium4]

The PSU from this post: https://www.badcaps.net/forum/showpo...postcount=1390

It will randomly shut off after 15-45 minutes, doesn't matter the load. Doesn't seem to be heat related. I saw it shut off once with a 50W load after 15 minutes, and it's lasted up to 45 minutes with a 300W load. Loading all the rails, such a strange issue. Soldering side looks good, all new caps. Maybe a partially shorted rectifier?

I want to get it working cause it's a decent PSU. Finally found info on the primary, and they are BJT's rated for 15A @ 25C. Only IC on the whole thing is an SDC2921. Can't find much info on it in English

Any ideas?

Here's the solder side:

[kaboom]

Re: Epower EP-600NE-XV Shuts down intermittently

Any ideas?

Sure! The Changs are "YHuCky."

When you say, "load doesn't matter," I assume you've got all rails loaded. When it does cut out, will it come back on by removing and reasserting the PS-ON signal via the green wire, or do you have to unplug, wait, and try again?


Do you hear any whining? Run the PS w/o the cover, and an AM radio nearby. You'll hear the switching harmonics at regular intervals on the dial. While under load, listen to the harmonics and note if there's any whistling, chirping or whining.

You'll have to tune around where there's no station broadcast, since if you've got a switching harmonic a few kHz away from a broadcast station, the resulting heterodyne will confuse you in this dirty little "test."

Do you have a scope?

[Escort Eagle]

Re: Epower EP-600NE-XV Shuts down intermittently

I also think so - it could be heat related . Is your Fan Moving Fast ? It also could be happen due to weakness of Two big Primary Caps or Secondary Output caps .

When it does cut out, will it come back on by removing and reasserting the PS-ON signal via the green wire, or do you have to unplug, wait, and try again?

What Kaboom said is also important . Are you getting +5VSB when it is shutting down ??

[Pentium4]

Re: Epower EP-600NE-XV Shuts down intermittently

Thanks for the replies. So....I brought it into work, and now it doesn't turn on at all! Just 5VSB. CPU fan ticks for a second when the power is hit.

Sure! The Changs are "YHuCky."

Thankfully, they're all gone now.

When you say, "load doesn't matter," I assume you've got all rails loaded. When it does cut out, will it come back on by removing and reasserting the PS-ON signal via the green wire, or do you have to unplug, wait, and try again?

Yes I had all the rails loaded. When it was working, I would need to unplug it and let the power drain, then plug it back in.

When it was working, and now not working, I can't hear any whining or chirping. All the secondary rectifiers tested good.

What Kaboom said is also important . Are you getting +5VSB when it is shutting down ??

After shutting down it still had 5VSB

I'm starting to think there's a problem with the IC? When just shorting PS_ON to ground, it will not turn on, but it gets 5.17V on the 5VSB, 0.00V on PS_ON and PG. Since this is a half bridge PSU, the chip has to be some sort of TL494 combo?

[momaka]

Re: Epower EP-600NE-XV Shuts down intermittently

The only time I've seen something similar was in a Linkworld PSU that had bad solder joint on the 3.3V rail toroid inductor. The joint itself looked good, but there was no continuity between the 3.3V rectifier center pin and the 3.3V wires, so it was only a matter of re-soldering the joints one by one until finding the culprit one. The PSU would only spin the fans for a second with that fault. Not saying yours has that particular problem, but double-check all joints regardless even if they look good. With the Linkworld I had, the problem was that they didn't strip enough of the enamel on the inductor's wire, so the contact area was very small.

Since this is a half bridge PSU, the chip has to be some sort of TL494 combo?

Probably. But there are many variations now. Could be just a simple 494 rewired, or straight 494, or maybe something like the 2005ATX. For this, you'll probably have to do a pinout tracing to see what the pins before trying a replacement.

Also, while the 5VSB may be stable, is the auxiliary supply (the one that actually provides power to the controller) also stable?

[Pentium4]

Re: Epower EP-600NE-XV Shuts down intermittently

Here's a link to the PDF for the controller: https://cdn.badcaps-static.com/pdfs/...1d9ec648b2.pdf

So, I looked at this thing again, and at first I thought that fixing this was going to solve the issue:


That must have happened after moving the wires around. I also found other inadequate joints and fixed them as well, but when trying to power on a system, the motherboard CPU fan would just tick (Not the PSU fan)

So I found another potential issue, the 5VSB output inductor was physically touching the 3.3V toroid. After separating them by wedging a piece of plastic between them, the issue remains, however now instead of a tick on the CPU fan, it makes a few revolutions instead AND now the PSU fan will tick as if it's attempting to start. Doesn't this seem odd? When attempting to power on, you hear a quiet click inside the PSU. No whining or other noise noticeable. When first plugging in, PS_ON gets 5.13V, and goes down to 0V immediately after hitting the power button. PG gets 0.016V, 0.028V briefly when the power button is hit, then goes back down to 0.016V.

[momaka]

Re: Epower EP-600NE-XV Shuts down intermittently

Maybe check for short circuit between rails? - i.e. between 3.3V rail and 5V, rail, 12V rail and 5V rail, and etc. Perhaps something could be shorted on the large toroid.

The controller appears to be an "updated" 494 variant, like the AT2005b and ATX2005 with direct sensing for 3.3V, 5V, and 12V.

According to the datasheet Functional Block Diagram, "REM" (your PS-ON signal) only appears to be an input. So I'm not sure if it is supposed to latch down to low (0V) like that. Check the VCC voltage on the chip and see if it's still there after this happens.

Other possibilities are some random small resistor to have gone open-circuit - but that is extremely extremely rare. More likely a bad solder joint.

Also check that one (or both?) of the BJTs on the primary side is not open-circuited. May have to disconnect some resistors on the Base pin for that, though - if you want to spare yourself from removing the BJTs (I would). Make sure both BJTs have a "healthy" B-C and B-E diode readings. And while in that section, check the Base drive circuit. That would be resistors R5 (which appears to be 1 Ohm?) and the second resistor next to D4 (same color code as R5). Check D4 and the other diode that's kind of hidden under the main transformer. Oh, and make sure the small electrolytic caps (C5 and C?) are not open or shorted.

[Pentium4]

Re: Epower EP-600NE-XV Shuts down intermittently

Maybe check for short circuit between rails? - i.e. between 3.3V rail and 5V, rail, 12V rail and 5V rail, and etc. Perhaps something could be shorted on the large toroid.

Thanks for the reply. Originally I tried upgrading the 12V rectifiers, and it wouldn't start with anything but the stock rectifiers. I may just replace all of the output rectifiers, since that seems to be the symptoms that the PSU is displaying. I have not checked the rectifiers since trying to swap them out.

Other possibilities are some random small resistor to have gone open-circuit - but that is extremely extremely rare. More likely a bad solder joint.

This is likely, since the more I look at this thing, the more terrible the soldering seems.

Also check that one (or both?) of the BJTs on the primary side is not open-circuited. May have to disconnect some resistors on the Base pin for that, though - if you want to spare yourself from removing the BJTs (I would). Make sure both BJTs have a "healthy" B-C and B-E diode readings. And while in that section, check the Base drive circuit. That would be resistors R5 (which appears to be 1 Ohm?) and the second resistor next to D4 (same color code as R5). Check D4 and the other diode that's kind of hidden under the main transformer. Oh, and make sure the small electrolytic caps (C5 and C?) are not open or shorted.

I have a strong iron, so removing the primary heatsink is no trouble I will do that tomorrow, will check those resistors too. I've recapped every cap with japanese parts, should I still check those caps?

I don't know if this could be a clue or not, but many reviews on newegg state the same issue, indicating that this thing could have a specific design flaw? Within reason I'd like to fix this thing, minor build quality issues aside, it's very solid looking

[momaka]

Re: Epower EP-600NE-XV Shuts down intermittently

Originally I tried upgrading the 12V rectifiers, and it wouldn't start with anything but the stock rectifiers.

Hmmm...

Were the originals MBR20100CT? If yes, try a Fast recovery rectifier - doesn't matter what current. I wonder if the slower recovery time of the schottky on the 12V rail has something to do with this.

I may just replace all of the output rectifiers, since that seems to be the symptoms that the PSU is displaying. I have not checked the rectifiers since trying to swap them out.

Sounds good.
This will also allow you to easily check if there is a short circuit between any of the rails themselves.

I've recapped every cap with japanese parts, should I still check those caps?

Yes, always check those. They can mess up the base drive signals to the BJTs. No telling if the PSU will just loose a slight bit of efficiency (the usual case) or totally malfunction.

I don't know if this could be a clue or not, but many reviews on newegg state the same issue, indicating that this thing could have a specific design flaw?

That's possible too. But then for the reviews that it works, that means at least some of the units must be done right. Or maybe a very very marginal design that depends on vary small component variances to work (ugh, that would be terrible... and unlikely, but not impossible).

Within reason I'd like to fix this thing, minor build quality issues aside, it's very solid looking

Agreed. Looks like a solid unit.
But you know me, I try to save almost every PSU possible - even the horribly anemic ones sometimes.

[Pentium4]

Re: Epower EP-600NE-XV Shuts down intermittently

The only time I've seen something similar was in a Linkworld PSU that had bad solder joint on the 3.3V rail toroid inductor. The joint itself looked good, but there was no continuity between the 3.3V rectifier center pin and the 3.3V wires, so it was only a matter of re-soldering the joints one by one until finding the culprit one. The PSU would only spin the fans for a second with that fault. Not saying yours has that particular problem, but double-check all joints regardless even if they look good. With the Linkworld I had, the problem was that they didn't strip enough of the enamel on the inductor's wire, so the contact area was very small.

Guys, momaka is a genius! Anything look funny with this mag amp coil?

[kaboom]

Re: Epower EP-600NE-XV Shuts down intermittently

Guys, momaka is a genius! Anything look funny with this mag amp coil?

I can't imagine...

Re-tin/resolder that lead, and maybe replace those secondary rectifiers.

Since it's a half-bridge, I'd also check the base drive circuits for the power transistors. Specifically, two signal diodes, and six resistors as detailed below. Use the attached diagram for reference, your supply will share the same circuitry, but probably not the same values or ref-deg's.

2- 1N4148s (D3, D4)
2- 1.8-4.7ohm, 2.2 being common (R6, R10)
2- 22- 47ohm, 39 being common (R7, R11)
2- 1.8k-4.7k, 2.7k, 3.3k, and 3.9k being common (R8, R12)



If you've replaced the two small electros (C9, C10), don't worry about them. Otherwise, replace 'em- they bias the switch transistors. They're usually 1-4.7u, depending on the unit.

Now, if you also suspect the two freewheel diodes (D1, D2), just replace them- as you've seen with diodes, they can "appear" ok, but are still bad. They commutate the current resulting from the leakage reactance of the power transformer- no transformer is perfect and not all energy applied to the primary gets to the secondary. Those diodes and the snubber network (hopefully) take care of that.

The fact that you need to unplug it for it to work again shows it's a latching fault, like outputs out of tolerance or overcurrent limit. Yes, it is possible to observe primary current in a half-bridge with a novel connection of the driver transformer. It's a turns-ratio-derived voltage that reflects (punny) and relates to the primary current. A diode, cap, and a few resistors feed this to a comparator, and this signal can, even in a "voltage-fed" half-bridge, prevent the supply from blowing up into a near short. Normally, a short across a half-bridge supply blows 'em. D14, D15, and C22 do this in the "atx supply."

Traditionally, current was measured with a conventional current transformer and associated burden resistor. See the Ludens diagram- T2 is the CT.

[momaka]

Re: Epower EP-600NE-XV Shuts down intermittently

Guys, momaka is a genius! Anything look funny with this mag amp coil?

Ha! QC PASSED!!!
Funny you have nearly the same problem in your PSU, even though it is from a completely different manufacturer. The 3.3v rail output toroid in my LinkWorld PSU didn't have ugly solder splat like that, though. Makes you wonder if the employees in that factory had a hot solder mini-wars just for fun .

However, I see another potential (lol them puns) problem with your PSU - those 3.3v toroids for the mag amp look like they are touching the secondary heatsink. Perhaps the coil you removed (or the one that is still there) are shorting to the secondary heatsink? I suggest putting a plastic insulation sheet or something.

[kaboom]

Re: Epower EP-600NE-XV Shuts down intermittently

Ha! QC PASSED!!!

Your caps must be good!

Funny you have nearly the same problem in your PSU, even though it is from a completely different manufacturer. The 3.3v rail output toroid in my LinkWorld PSU didn't have ugly solder splat like that, though. Makes you wonder if the employees in that factory had a hot solder mini-wars just for fun .

Aren't they not allowed to talk, or even look, at each other? Oh, wait- that's FoxCon(ned)!

However, I see another potential (lol them puns) problem with your PSU - those 3.3v toroids for the mag amp look like they are touching the secondary heatsink. Perhaps the coil you removed (or the one that is still there) are shorting to the secondary heatsink? I suggest putting a plastic insulation sheet or something.

If that edge is poking through the varnish, then maybe so. With heat and movement, it could (partially?) explain the "randomness" of its problems.

[Behemot]

Re: Epower EP-600NE-XV Shuts down intermittently

Oh my WTF with that toroid

[Pentium4]

Re: Epower EP-600NE-XV Shuts down intermittently

I can't imagine...

Re-tin/resolder that lead, and maybe replace those secondary rectifiers.

Since it's a half-bridge, I'd also check the base drive circuits for the power transistors. Specifically, two signal diodes, and six resistors as detailed below. Use the attached diagram for reference, your supply will share the same circuitry, but probably not the same values or ref-deg's.

2- 1N4148s (D3, D4)
2- 1.8-4.7ohm, 2.2 being common (R6, R10)
2- 22- 47ohm, 39 being common (R7, R11)
2- 1.8k-4.7k, 2.7k, 3.3k, and 3.9k being common (R8, R12)

Thanks, Paul. This will come in handy I'm still testing components...Haven't found anything bad so far. However, notice the BJT's. They're the same, but notice how the printing was done in different sizes, and the way they cut the leads on the right one


In the mean time, I also have an SDC2921 coming in the mail, in case the one I have is bad.

However, I see another potential (lol them puns) problem with your PSU - those 3.3v toroids for the mag amp look like they are touching the secondary heatsink. Perhaps the coil you removed (or the one that is still there) are shorting to the secondary heatsink? I suggest putting a plastic insulation sheet or something.

They were retinned, no luck still I know it looks that way, I think it's the angle of the picture. They're both ~8mm away from the heatsink in both directions. If that's still too close I can move them, but that seems like a safe distance.

[kaboom]

Re: Epower EP-600NE-XV Shuts down intermittently

You should be able to power up the '494 with an external supply. 12-18V. Use secondary common for the return. Look around for either the cathode of an isolating diode or the cathode of a dedicated aux "pick-off" rectifier, such as the one connected to the top of C21 (22u/16V) in that diagram. If you connect to the right place, the entire control section will run, but none of the outputs, including +12, will come up. So the PWM runs at full (minus dead time) duty cycle.

Then, you can scope the bases on the primary side safely, since it's unconnected. You should have nice symmetrical waveforms.

When scoping those base drives, you must put the scope tip/gnd, respectively, across the base/emitter leads. Pull the switchers, too- the B-E junction will pull the positive excursions down.

Or, you can try with a DMM set to AC volts. You're not interested such a meter's high-freq accuracy- trying for a relative measurement here. Both transistors' B-E drive voltages should be the same, and also add up- they're driven 180 degrees out of phase. So if each one gives ~1.2V, checking base-to-base should read ~2.4V. Again, that's just a quick test to check for any action coming from the driver.

You can also check with a "freq count," if your DMM can do so.

[ben7]

Re: Epower EP-600NE-XV Shuts down intermittently

Thanks, Paul. This will come in handy I'm still testing components...Haven't found anything bad so far. However, notice the BJT's. They're the same, but notice how the printing was done in different sizes, and the way they cut the leads on the right one


In the mean time, I also have an SDC2921 coming in the mail, in case the one I have is bad.


They were retinned, no luck still I know it looks that way, I think it's the angle of the picture. They're both ~8mm away from the heatsink in both directions. If that's still too close I can move them, but that seems like a safe distance.

Wow those transistors look kinda screwy (AKA cheap). Interesting that they aren't the all too common MJE13009.

Wow I never would have thought to check the insulation on that mag-amp coil. Haha reading this thread made my day!

[momaka]

Re: Epower EP-600NE-XV Shuts down intermittently

Haven't found anything bad so far. However, notice the BJT's. They're the same, but notice how the printing was done in different sizes, and the way they cut the leads on the right one
https://www.badcaps.net/forum/attach...1&d=1424224095

Wow, they do look quite goofy. I wonder if one of them went open-circuited. It's a rare failure mode for BJTs, but it does happen. That could also explain the fan "blip" you see on the output.
If you still have them out of circuit, check their B-E and B-C PN junctions... i.e. set multimeter on diode test mode, put red (+) probe on the base (B), and black (-) probe on emitter (E), and then collector (C). You should get a healthy diode voltage drop on both - probably around 500-700 mV (usually around 600 mV).
- OR -
If you have a crappy PSU with 13007 BJTs (or something equivalent), try swapping those into this PSU.

Another thing I would suggest you check - the 3.3V rail mag amp circuit. In the schematic diagram that Kaboom uploaded (200W PSU, "DTK PTP-2038"), that would be on the lower right of the picture - you should have a circuit similar to that in your PSU. Should be a small transistor (Q13 in the PTP-2038 schematic), a diode (D32), and a 431 shunt IC.

Finally, check that none of the silicone parts - both on primary and secondary - don't have their tabs shorting to the heatsink.

I know it looks that way, I think it's the angle of the picture. They're both ~8mm away from the heatsink in both directions. If that's still too close I can move them, but that seems like a safe distance.

Yes, that distance is more than enough. If your voltages on the secondary side are jumping 8mm air gaps, you'll probably have bigger problems

[Behemot]

Re: Epower EP-600NE-XV Shuts down intermittently

I think that EU norm is at least 3 mm of air insulation so 8 mm is just OK.

[kc8adu]

Re: Epower EP-600NE-XV Shuts down intermittently

different counterfeit parts with different markings.
but why?
bjt's are too cheap to be worth all that.