Delta DPS-400GB-1A Troubleshoot (xserve)

[brianc]

I bought an xserve with a dead PSU thinking I could fix it.

Nothing is obviously burnt, it doesn't blow fuses, it has 0 volts output. The xserve manuals says it should have +12v on standby. According to the manuals there are 2 rails of +12v, and 3 IIC pins. No other voltage outputs.

I do have a HP 54501A 100mhz, and a voltmeter.

I am getting no output from the primary transformer. (the transformer between the mosfets and the output filters)

Measuring the input to the transformer, from earth, the scope shows -101.6vmin, 78.125vmax 179.7vpp, @ 60hz. This is a distorted sine wave with a sharp peak on the upside and a fast rise and a tapered fall.

Both inputs to the transformer are identical, so checking between the 2 inputs reads 0v.

I am unsure where I should be looking to solve this problem.

[Th3_uN1Qu3]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

The scope won't say much in the primary of a switchmode supply unless you have an isolation transformer to plug the power supply into (scope must always stay earthed!!!). Anyway, it sounds like you do have voltage on the primary capacitors. Confirm this with your voltmeter, it should be close to 1.4x AC line voltage.

Sounds like a dead standby switching transistor. They usually blow open. No output and no blown fuse sure fits the description. Also check for bad small value capacitors in the area, they are usually 50v rated. One of those gone open could cause the SMPS controller to stop working even if the transistor is fine.

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

I do have 167v across the primary capacitor. I cannot find any bad caps, they all seem to charge, then open.

I will replace all the transistors and see where that gets me. They are 20N60C3. I have 3 total.

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Apparently these mosfets are obsolete.

They are Infineon Technologies 20n60c3 in a TO-247 package.

600v, 208watt, etc.

https://cdn.badcaps-static.com/pdfs/...10059ad10f.pdf

These should be able to be replaced with any standard mosfet with similar specs correct?

[Th3_uN1Qu3]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Yes. Look for matched (or lower) Rds(on), higher power dissipation, and equal or lower gate charge. But doesn't it have a separate standby supply? I don't think the main switchers are the culprit.

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

This supply only has 2 +12v rails and nothing else. From what I can tell, one of the mosfets supplies power to the control circuits and seems to be working, while the other 2 mosfets switch the leads to the transformer which powers both 12v rails. according to the server manual there should be 12v on o e of the rails in a plugged in standby condition.

Thanks for the help. I am going to have to order the mosfets. Infineon seems to be the only people that make them with the specs I need.

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Pictures of the board and components:

[Toasty]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Not the MOSFET's. Unblown fuses are the first clue.

As was mentioned, the caps between the blue coil and the other side of the small transformer, under the "L" shaped heatsink, are the likely problem. A -lot- cheaper than chasing obsolete FETs.

Your scope probe just held -near- the transformer should be giving a nice ringing wave form, not a sine wave. Looks like a pyramid on its side pointing to the right > . Set the scope for ~20mV and 10µS.

Does this have any type of standby voltage output?

BTW: Please don't post pics inline that are this big. Use the attachment feature under "Go Advanced". I'm on a 24" widescreen monitor and they're 4x larger across than my screen.

Toast

EDIT: No wonder this looked familiar... What's the Apple P/N ?

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

I resoldered the small transformer after a failed attempt to remove it.

The psu turned on! I could hear the buzzing and the relay click on.

I shut it off quickly so I could setup my voltmeter to test the output and when I turned it back on... nothing.....

Looking at the small transformer with the scope as toasty suggested, it appears as though it is trying to turn on, there is a ringing waveform about once a second, the big transformer is quiet.

I am going to start swapping caps out near the small transformer and see where I get.

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

EDIT: No wonder this looked familiar... What's the Apple P/N ?

614-0264 400w G5 PSU

[Toasty]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Ahh, good! The heat from soldering the transformer warmed a nearby cap. Sometimes the "hair dryer" trick works. Sometimes the freeze spray.

Toast

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Well I replaced all the caps near the smaller transformer and SUCCESS!!

PSU seems to be working just fine now. I have 12.18v on both outputs. It powers up the server fine. These supplies seem to be ON as soon as the cord is plugged in, which is probably why they burn out often.

Thanks for all the help!

[Toasty]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Might as well recap the rest of it. It doesn't have that much in the way of output filtering, so any upgrade will help in the long run.

Glad you got it fixed.

Toast

[POM_MJ]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Could you add informations and some pics of the bad caps (for reference to another) ?

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Could you add informations and some pics of the bad caps (for reference to another) ?

Pics might take me a while. Supply is tucked back inside the server.

The caps didn't actually look bad, and seemed to test OK with my voltmeter. They must only go bad under load. There are 100micro25v on either side of the small transformer, another 100mF25v, a 10mF50v and a 47mF16v on the secondary side of the transformer that I replaced.

The primary switching mosfets were inactive during initial testing. There was some voltage on the output of the small transformer. On the scope I could see that the supply was acting like it wanted to start up when looking at the ringing of the small transformer as suggested by Toasty.

The filtering section on the 12v lines has 2x 2200mF16v and 2x 1000mF16v caps.

I replaced all caps with equal Farad values, but higher voltages.

[POM_MJ]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

I would like to know the failed caps brand and series, TAICON PJ?
some of Delta's low class psu used TAICON or Ltec.
Thanks.

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

The two that were closest to the transformer are labels as LTEC 100mF35v 4415D.

The rest are TAICON, the 10mF50v reads 0423(M) 105C(VF)

Here is what I was able to rescue from the trashcan.

[brianc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Time to bring my thread back!

Bought another spare broken psu off ebay.

Looks like its the same issue as the original. Going to replace all caps first thing.

What are some quality brands of capacitors?

[mcnaryxc]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

Hey, thanks for your thread, I was able to try and successfully fix my Xserve G5 power supply. However, I didn't do exactly what you did.

Instead of just replacing all capacitor I could see, I decided to try and find which capacitor was the problem. With the power plugged in, I was testing the voltage on the capacitors with my $2 multimeter, seeing if any were stuck open. As I was testing out the caps near the middle-sized transformer, one of the solder spots of a cap I was testing for voltage started making sparking sounds. It scared the heck out of me so I pulled away really fast, and the amazing happened. The power supply kicked into standby, making a humming sound. I was skeptical that perhaps I hit something weird (since my hands are always shaking when working on power supplies) so I unplug/replug the cable and try again. Sure enough, it make the spark sound and turned right on. Alright! I found the problem! (attached is an image with the cap marked that is bad)

So, I go to extracting it. There is so much white glue stuff around it that I almost rip off the label and can barely make out the specs. The cap is a Ltec 22microF 25v cap. To my amazement, Radioshack actually sells this capacitor (22microF 35v), so a quick run there with a $1.29 and run back. Soldered in the new cap, plugged in the power (while crossing my fingers), and it turns on!! I was so happy. I thought I was going to have to buy a power supply off eBay, which is expensive.

I don't know if this was your problem or not, but it helped me. Hopefully it'll help someone else.

[Th3_uN1Qu3]

Re: Delta DPS-400GB-1A Troubleshoot (xserve)

That position is going to do fine with a radio shack cap. For anything else order from here or digikey.