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revengineer

Sans Digital Power Supply Issues

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revengineer

Afternoon,

In 2011 I bought two Sans Digital TR4UTBPN (USB3+eSata) 4-Bay external drive enclosures, which have served me well until recently. A few days ago I shut the server down to clean out the dust bunnies, and when I tried to turn the enclosures back on, they wouldn't. All LEDs on both enclosures stayed dark.

 

I took the assembly apart and traced the issue down to the power supply; 110V goes in, but no voltage on either the +12V or +5V output. Searching the internet I find that the power supply is the weak spot of these units. Most negative reviews on Newegg and Amazon are due to power supply failure. (Some were due to drop in connectivity, but this is because one has to find the right USB3 card for these enclosures to work right.)

 

Since there are so many complaints about the power supply, there must be a common point of failure and I was wondering if someone here knows what this is. Visual inspection showed no burns or popped capacitors. I did some limited in-circuit meter testing to find switching transistors and rectifier diodes in working order. The fuse is also in tact. If anyone had a similar issues, I would appreciate a response.

 

(I know that Sans Digital sells replacement power supplies. But since these units come at $60 plus $20 shipping, I thought I try the repair option first before I fork out $160 for two of them.) 

 

Thanks in advance for any pointers.

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schoondoggy

Is there any part number or manufacturer identified on the power supply?

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revengineer

I googled the markings on the pcb but nothing came up that looks like it. But pricing for similar boards are around $30 so Sans Digital is putting a hefty markup on their parts.

 

I like having the supply in the boxes but as a work around I could even use a single external pc power supply to power both boxes. I keep this as an option in mind.

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revengineer
The power supplies linked do not include the transformer part. Fitting this plus the regulators in the box will be tight. Also it will need to be a switching power supply.

 

Repair is still my first choice. If that does nothing to work, I may consider forking the money for replacement supplies.

 

I did sent email to Sans Digital asking for any Insight. I don't have much hope but it's worth a shot.

 

Finally an engineer from work agreed to take a peek, just not sure when he gets around to it. If he can find the issue in 30 min or less it's worth the effort, especially since this problem will likely reoccur in the future.

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schoondoggy

The parts I linked above are just the regulators to give you the correct voltages from a single DC voltage. If the supply only delivers 5VDC and 12VDC you could try a external supply that terminates with a 4 pin Molex connector. The power supply is listed at 150W. I would look at it as 4 drives and a circuit board.

Grabbing a HGST data sheet for a 5TB drive, power consumption is highest at startup; (1.2A, max +5V, 2A @ +12V)

For four drives you need 4.8A on the 5VDC and 8A on the 12VDC. It is hard to tell the power required for the circuit board, it is probably mA, but just to be safe add 1A to each voltage: Total 6A 5VDC and 9A 12VDC. Total of around 150W.

 

What are the physical dimensions of the supply?

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revengineer

Understood about the regulators. That's why I felt it's not going to fit. The present power measures about 2.5 by 4 inches. If I cannot fix it, I would have to go the external route.

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revengineer

Just a quick follow up on the issue. I have received replacement power supplies for my two enclosures. Replacing the power supply did indeed fix the problem and I now have two replacement units in case the new enclosures I purchased fail. This is almost a given since the power supply in the new units is identical to the old one. Oh, and did I mention that one of the replacement power supplies came DOA?

 

We still did not debug the broken power supply so I cannot yet report which part is broken.

 

It's too bad that these units have such poor power supplies because they are a great product. I find them more appealing than the Mediasonics boxes and much cheaper than putting something together in a norco box. When I have some cash, I will build that 24 bay norco case, but at the moment the family has other priorities.

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Indycanard

Just last night, after being off for two weeks, by Sans Digital external enclosure failed to turn on, exactly as you describe. This same thing happened to this box almost two years ago, and at that time I did a fair amount of troubleshooting to the power supply, but I had no luck determining why it would not turn on. I did the usual checks, bad caps, bad fuses, burned components. Nothing found. I ended up buying a replacement power supply from Sans Digital. This "new" power supply is what failed last night.  I had a second Sans Digital enclosure that is dead with the same issue.  I'll tear into this newly failed power supply tonight and do the usual checks, but I don't think I will have the expertise. 

 

This is a VERY common problem (from the many on-line complaints I found - including yours), and I don't think Sans Digital has any motivation to step up and fix this issue. I'm hesitant to spend more $$$ for a 1-2 year fix.

 

If you are able to get your engineer to take a look at yours,  and are able to figure anything out, I'd really like to know what you find. If I find anything, I'll post it here. 

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Indycanard

Initial troubleshooting has begun, and already I found what I think may be a problem.  Tracing the power onto the board looks great, all fuses are good, and the physical power switch works good. I can trace the +120(RMS)VAC from the power connector on the board, thru a filtering coil, and then to a bridge rectifier. That is were I'm stuck (or I found my problem).  The 120 VAC is connected to the center two pins of a GBU406 full bridge rectifier. The measured AC voltage (via a cheap VOM) is 120RMS VAC.  The VPeak voltage should be 1.414*RMS = 170VAC.  The outer two pins should be rectified to DC, and according to my calcs should be appx 0.637*VPeak = .637*170 = 108VDC (with load) . I directly measured  328 VDC!  This has me stumped. Now if I assume no-load, I should measure appx 168VDC rectifier output.

 

Can anyone more enlightened in power supply and more specifically bridge rectifier theory explain why I'm measuring twice the expected voltage for an unloaded circuit?  If the rectifier is bad, I don't see how the voltage would be doubled. I may just replace the rectifier and see if I measure the same voltages.

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