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Switcher Repair Hints

Hi All,

I still enjoy this forum, even though I have to sift through the spam. It's a real shame.

I have a Supermicro computer with a 'triple redundant' power supply. That means 3x250 watt modules in a backplane and rated at 500 watts. You can loose one module and still be in spec.

I lost a module, had it repaired under warrantee, and lost the the same module again. It is an Ablecom Model SP 252-TC and I can find nothing on it, including the card edge connector pinout. It looks very well made and it I see quality components crammed inside. Supermicro P/ N is PWS-0035(M). Some research indicates it may have been made by LiteOn.

The module will run for 30 seconds, then shut down for 20, then repeat. An 'amp clamp' on the input shows about an amp when it's up, and less than 100 mA when it's down, so I have to figure out why it decides to give up and retry.

I could really use the edge card pinout of this type of supply and any hints as to this type of symptom to save me reverse engineering time. I'm thinking thermal, and if I can coax the supply into operation on my bench, freeze spray will probably indicate the problem in short order.

I am aware of proper safety procedures.

Thanks in advance!

Jim S.

Reply to
jrshedden
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I have not worked on that particular supply. I found that on most of the supplies that I have serviced, they had caps that failed or became thermo sensitive.

What I can suggest to get an ESR meter and test all the caps. Heat the module up with a heat gun so that it is warm when testing the caps. All the caps that read too high in ESR should be changed.

If the fault is more complicated, the supply will be very difficult to service without the schematics and a source for the proprietary parts. In the modern supplies they use a lot of SMD technology with very specialized IC's, custom made transformers and inductors and devices.

As for myself, I found that the majority of times these supplies are not worth to service. You can end up spending many hours and a lot of money on parts. In the end you may have a supply that you cannot have some specialized parts you need and you spent a lot trying to fix it.

Jerry G.

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Reply to
Jerry G.

On Fri, 15 Aug 2008 12:30:37 -0700 (PDT), jrshedden put finger to keyboard and composed:

All I could find were the ratings of the outputs:

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The obvious thing to check when you suspect thermal problems is the fan.

Otherwise, with the unit powered down, can you probe for continuity between the backplane pins and known voltages on the motherboard (eg PCI slot) and peripherals?

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I've never worked with a redundant, hot swappable PSU, so I don't know if what I'm asking makes any sense.

- Franc Zabkar

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Please remove one \'i\' from my address when replying by email.
Reply to
Franc Zabkar

Hi,

Thanks for the 2 replies. I hope I'm properly posting so you both can see this. Am I correct that a 'Reply' is to all and a 'Reply to Author' is in response to a particular post?

Franc:

Thanks for the pinouts. There are 3 backpanes in the server. Once is the motherboard I/O expansion (PCI-X and PCIe on this one). The second is the SCSI backplane where up to 7 disk drives plug in. The third is the power supply backplance (Supermicro calls it the 'power distributor') where 3 identical 250 watt power supplies slide in from the back of the machine and connect via edge card connectors. Each power supply has its own power input and its own fan, so the server has 3 power cords. When the supply goes down, its fan stops because it probably runs off it's own 12 volts, but it is going strong when the supply is up and the exhaust temperature matches the other 2 within 3 or 4 degrees F.

Jerry:

I built the Dick Smith ESR tester, and I will check all the caps when heated. I'm taking your advice and replacing the supply, but I will probably hack around the module to see if I get lucky. It will take some luck or an inordinate amount of time without schematics.

Solution:

ACS Industrial services would fix the module ($250 minimum) and Supermicro would sell me a refurbished 760 watt triple redundant (3 modules + backplane or power distributor) for $300 or $330 (I forget). It's ordered and on the way. Too bad the &60 watt modules are not compatible with the old backplane.

If I figure out the module problem I will repost the result.

Thanks for the help.

Jim

Reply to
jrshedden

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