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Re: Server converted power supplys.

Posted: 15 Mar 2018, 22:26
by sureshot
This is only a small offering, literally. I had to give it a few days of use to see if it behaved reasonably. As most come here looking for "BIG POWER" this might not be for everyone. Although it does cover a multitude of sealed smps units.

The one below was surplus from some old thin clients I had. I started by measuring the voltage whilst the unit was intact. Then the case was split by scoring round the case edges multiple times with a sharp stanley knife. On opening it up I had a quick scoot around the pcb, make sure all capacitors looked ok.

As the wires to the lead had age hardened I decided to replace them with twisted pairs, total wire capacity could carry 8 Amps. As this is a 12 Volt 4.16 Amp power supply, I thought that adiquate. There is no space for terminal or binding posts in this, so I had a rethink and used good quality speaker terminal plate with spring back terminals. I've seen these on retail units stating up to 5 Amps current. If you get good quality ones you could go to 10 - 12 Amps easily with these terminal plates.

Mounting the terminal plate was easy, but I did use nylon machine screws, there are two internal heatsinks, whilst they might be at a low potential I was not taking that for granted. ( in times gone by I've come across heatsinks in atx units that where at mains potential) Put a piece of card glued over the soldered terminal. A test whilst the unit was in two halves, all looked good so it was reassembled. Standard araldite epoxy worked great, allowing over night drying. Tape or a small clamp does the job nicely.

As I don't have a scope at the moment, it's a case of taste it and see. No problems powering an 80 channel cb and an old tagra 25 watt linear amplifier.
Some overs later and all seems fine, current drain was just over 3.2 Amps with that load combination, voltage drop 0.2 Volts under load. So it won't win any prizes in terms of power, but for what it is I'm pleased with it. This process could be adopted to many sealed smps type units, this is what I had laying around.

I'm tempted to look for an oscilloscope, but eBay has only junk, I've got my eyes on a 40mhz hand held unit, might invest in one. It would be interesting to see ripple noise for a known load current, with any smps. Next offing will be back to big server units. Hope some can see potential in this modest offering. :)

Re: Server converted power supplys.

Posted: 16 Mar 2018, 12:17
by kilimax
Some interesting posts Sureshot. :thumbup:
I have 2 large boxes stuffed full of power supplies of various types, most are rated at 12 volts, a few are somewhere between 5 & 9 volts.

While I don't see me having the need for something like this, I may look out some of the larger 12 volt bricks and see what they're like.

Re: Server converted power supplys.

Posted: 16 Mar 2018, 12:21
by MrWeetabix
Cracking little project.... be nice to re-purpose some older PSUs. That one from the thin-clients would be ideal for someone who was travelling. Much easier to pack than a 3/5 standard CB PSU or similar


Re: Server converted power supplys.

Posted: 16 Mar 2018, 13:16
by sureshot
Thanks for the comments guys, yes there are lots of sealed psu units that could be viable for use. Couple of pictures for size scale. The 3 - 5 Amp is a standby power supply. But as for the little hp smps, you could put it in your pocket its that small.
If your needs are modest, this type of psu might do you fine. :)

Re: Server converted power supplys.

Posted: 12 May 2018, 22:00
by sureshot
Give this a mention, but only the one image.
Bet somewhere in the country, world for that matter. Is currently pulling there hair out with a noisy power supply fan. This is for the Xbox 360 power supply grey brick 175 watt version (different technique for the other two models of grey brick psu ) I've not attempted them yet, as heatsink runs the length of the unit in the 203 watt psu.
This one's fan was sounding like a cement mixer, quick explanation.
Unpowered ! Remove the lid after taking out the four selftaping screws. Snip the fan lead as close to the old fan lead as possible. Find a 40mm axial fan with as low as a power rating as you can, I suggest sunnon fans.
Next remove all the plastic ducting in the top half of the case from the inside, including the old fan.

You will see a rectangular recess in the case rear where the old fan was located. Centre that recess drilling a pilot hole, use a 38mm wood spade flat bit. It must be sharp, drill slow half through one side so you break the surface with the 38mm bit. Now come in from the other side until your through the case. Slow and steady so as not to crack the case. Expect noise and mess :D
Now line up your fan drilling 4 x 3.2mm holes for the new fan and guard. 20mm M3 machine screws work well with washers and nuts. Once fitted dry fit the case lid, making sure no screws touch any internal metal parts, heatsink etc. That bit is very important to check.
Now strip back enough of the internal fan lead and bare the two wires, + - Shorten your fans flying leads, so you've got enough to solder both leads. Push heatshrink tube on before solder leads.
Solder the leads, shrink the tube over the spliced leads. Route the cable such that nothing is fouled, and is neatly tucked away from the fan blades. Use hot glue if you like. Refit the case halves and power on to test. Quiet fan years more service happy days.

At some point I will tackle the 12 Amp and 16 Amp grey psu bricks, as there fans are just as likely to be worn out over the years. :)
This modification is for the 175 Watt 14Amp unit.

Re: Server converted power supplys.

Posted: 30 May 2018, 22:38
by sureshot
Been looking at something a bit different. I don't have big amplifiers like RM KL 500 or Zetargi high power amps. But wanting to test these different server power supply, whilst using the amplifier I have. But with the psu loaded down quite a bit, really just to see the effect of ripple on the psu output whilst a modest amplifier is connected. And loading it down. I don't have the means or area to put together a precision load device. But at the same time this is very high current, where precision resolution isn't really necessary.

What I've got is a replacement for halogen lighting as a load piece of test gear, be it homebrew. I hope to find a modest oscilloscope sooner or later, and this load device will be interesting to see the output waveforms under load. And also while driving a modest amplifier. The idea being it could then in theory drive large amplifiers in place of the load device. I would rather prefer a psu failure if any, connected to a load and modest amplifier, as this will shut down before it goes South if that was to ever happen.

To the point now...
It's a pair of 100 watt heatsinks with three high power resistors on the interface. I couldn't think how to get super close power ratings, so it's 220 watts to 300 watts and from 12 Volts to 14 Volts input. Two fans for cooling to dump that heat, and another fan pulling it out of the case. I did want to go to 500 watts loading, but the case and metal structures where a bit beyond me at the moment. It's sourceing heatsinks and cases large enough to house a 500 watt load. So 220 - 300 watt it is. I'm using relays for longevity, although not really necessary. The host power supply is put in to the 30 Amp front posts, this is idle until one of the six switches powers one of the resistors. And so on up to all six if needed, or as little as one resistors for loading. It can be used equally on linear power supply as well. It is just resistive load, as a combo of inductive and resistive would need much more space.

The host psu under test powers the connected amplifier and any added load resistors. The panel meters will show any voltage drop under load, at also status of power / current being drawn from the host power supply. Six toggle switches and corresponding relays control each load resistor and status led. Two fan lights for each fan when there powered on, using thermal switches to control these. No fans needed at light loads, and two thermal switches via another power relay to cut the input and load in the event of a fan out or fault. And finally a crowbar to cut the power if the voltage climbs to high. Unlikely in modern server power supply, but best to be on the safe side to protect any connected equipment. I hope to get in real time use, some conversations with locals, and off shore contacts if there are any. As any strange behaviour from the power supply would certainly show if it was unhappy with the load it's under. If the units I use as hosts work well under increasing load, less any horrible noises coming across in TX and RX, I would consider that power supply a successful one.
Just the one image at the moment, it's early days. Hopefully more to follow soon.
Any thoughts always welcome. :)

Re: Server converted power supplys.

Posted: 31 May 2018, 22:59
by sureshot
A little bit more progress, these heatsinks are rated at about 100 watts a piece. Not less the material missing for holes, it all counts. At 12 Volts it works out at a maximum load of 221.5 watts, at 14 Volts it's a maximum load of 301.5 watts. So at the nominal 13.80 Volts it's a load of 292.9 watts. It's pushing it a bit at 300 watts end of the scale, but with a 100 watt cpu temperatures are around 45°C with around 65 - 75 % fan speed. These resistors are rated at 150°C. With a fan at 100% things should be around 85 - 100° C I'm hoping :D might be less 8) If needs be I can over drive the fans a little with a small boost converter. I did um and arr about using these heatsinks, as I noticed the bulk of the aluminium is not uniform across the whole heatsink. It kind of has a convex profile where it meets the cooling fins.

Trying to space the power resistors as best as possible to get even heat distribution, had I gone in the other direction the two outer resistors on each heatsink would have run hotter. For a cpu it's of no conciqence, but I've had to stagger the resistor layout for what looks like best even thermal dissipation.
That's it for the moment, not to grim with out a drill press. Although you really do have to concentrate to avoid wandering or elongated holes, neither luckily.
More to follow when I get to the front and rear case panels. Then finally the wiring up. I've wanted to use a digital meter for a while now, but thrashing it out on another forum I was informed they tend to drift somewhat with time. So analouge meters it is this time.

Re: Server converted power supplys.

Posted: 03 Jun 2018, 22:20
by sureshot
Some more progress...
It's a passive unit really for load testing, I realised I missed out the relay bank, and two bus bars in the form of 30 Amps terminal blocks. after I'd taken the pictures. It's really quite a simple construction. Had an rarer moment when I slipped whilst deburing the holes, slight scratch I know it's there. Annoying, might blow some spray over it yet. Or liven it up with some colour.
These boxes are off eBay, the shells are tough rugged plastic abs type stuff. But the front and rear panels are more a polyethylene or polypropylene type material. The drill grabs, even when using progressive drill bits. Still a crowbar circuit and fan board to put together.
Bit of wiring up soon... :)