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Thread: Server PSU mods for bench power supplies

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    Default Server PSU mods for bench power supplies

    So, is anyone into modifying these server supplies to power, well, about anything from battery chargers, auto diagnostics, to LMR commercial radios.
    I have a Liteon 84 amp supply I want to up the output voltage from the 12.4 V max to 13.8 V to replace an old analog 30 amp bench supply.
    More than double the power and 1/5th the size.
    I also have some AcBel 550 watt supplies that would be perfect for running commercial LMR radios like 110 watt Motorola ham, or any of the branded ham radios. (Yeasu, Kenwood, Icom, etc.)
    My stumper here is finding schematics for the OVC and over current controller boards. They seem unobtainable.
    There are plenty 'how to's' on youtube, but I really need the technical info for these.
    They are not 'mini-Ha Ha' supplies, they are rock solid, clean, small footprint power source.
    Any help here would be hot, or you folks might look into these for projects.
    TYIA



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    With most equipment stating 'automotive nominal' input voltages of between 13.2v ~ 13.8v DC, they work just fine on 12.x volts DC -- ergo, first ascertain if you need to do anything at all.


    edit: just to answer this one...

    My stumper here is finding schematics for the OVC and over current controller boards. They seem unobtainable.
    These details form part of the 'IP' (intellectual property) of the manufacturer, and rarely gets released into the wild. The details are available, one just needs to provide their own intellect =)

    *examine PSU to determine what controller IC(s) are used -- grab the datasheets for same
    *reverse engineer the circuitry/components used to implement these devices -- reference results against datasheet application circuits/operational values to determine what the PSU manufacturer has done.
    Last edited by wotnot; 12-11-21 at 03:13 PM.

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    Hi.
    There are just too many uses where voltages below 13.1 volts won't work. An example is BMW system scanning. Recommended is 13.4 volt @ 75 AMP. (min)
    Charging batteries usually means up to 14 volts
    These supplies can be paralleled with a load sharing pin (any number) but the voltages must be matched to less than .50 volt.
    I have been reverse engineering these, IC datasheets etc. Not easy with poor eyesight and have over a month on this project.
    Price a 100 amp lab supply, that starts at $1000. Generic regulated supplies over 50 amp start at $350 and up.
    These server supplies can be had less than $100. (a box of 6 X 80 amp cost me $150) so go figure.
    Just the ATX supplies make great bench test supplies with 3 V, 5 V, +12 V, - 12 V. Just a matter of turning them on out of a computer.
    Last edited by Hunchback Tech; 12-11-21 at 11:40 PM.

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    Here are a couple photos of just the controller board, as you can see, high density micro SMT.
    This one, I destroyed the V adjust pot for too much soldering resistors. I think it can be repaired (fudged) with a trim pot if only I had schematics.

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    An example is BMW system scanning. Recommended is 13.4 volt @ 75 AMP. (min)
    I imagine that's required vehicle voltage/amperage at battery B+ ... it's got nothing to do with scanner requirements...ie; recharge/replace car battery if this condition cannot be met.

    I have been reverse engineering these, IC datasheets etc. Not easy with poor eyesight and have over a month on this project.
    Can't help you with that, it's pretty much a standard issue task if one want to hack stuff like this =) That is to say, every manufacturer uses a different design or topology, different components and/or values of components, and typically only someone who's traveled the same road, with the same model PSU (and sometimes model isn't enough and must be the same PCB revision as well), and has figured out the feedback/protection circuits can be of any immediate help to you (being able to answer the question 'what do I need to do to -this- PSU to make it do 13.8vdc?') ...and then looking to overrate the 12vdc output by >10% ...there's going to be multiple changes needing to be made, no way will it be as simple as just bumping the voltage value up. When they make them they aim at a specific specification, and they choose everything with a glass-slipper fit.

    These supplies can be paralleled with a load sharing pin (any number) but the voltages must be matched to less than .50 volt.
    These server supplies can be had less than $100. (a box of 6 X 80 amp cost me $150) so go figure.
    They're cheap, for a reason -- you have to figure out what that reason is =) Typically with decommissioned/redundant server stuffs, it's because things aren't really plug'n'play, you have to provide 'something else', and invariably there is little or no documentation in the wild --- you are on your own <grin>...server rack fans spring to mind, beautifully machined & balanced, 3phase brushless motor, screams like a banshee as it pushes huge volumes of air....but all the driver electronics are on the server motherboard, so to use them it's byo ESC and pulse controller.

    Wrt something like this...getting computer power supplies to do something else, provided you want to stay within the standard ATX specs, it's as easy as buying a $5 breakout board, and you're done. I toyed with this idea, but really the sort of gear I see on the bench could be anywhere between 24 ~ 48vdc, so I found some cheap Lucent es460 units (48v -/+ 4v adj, 10amp), can be paralleled (active or passive), and use a Riden DPS5015 to regulate whatever output I need. There's a thread here somewhere about the es460c PSUs, they're nice bit of kit, but, all the docs/manuals are closed source IP, and with this gear the users are supposed to return it at decom time...and for relevance to this forum, *worse* than /\/\ ... =) Fortunately someone scribbled down some details of the 16x3 din connector, enough to get them up and running as power bricks.

    These days, what's possible with protection circuitry, can end up as code OTP'd into some power management/supervisor IC, and if this is the case it looks like a brick wall to me ; but that'd be key here - I don't know what I'm looking at.

    Which leads me back to the above - all PSUs are different at circuit/component level, and without a schematic, reverse engineered or otherwise, it's nigh on impossible to give you any advice/help specifically due to the number of variables involved.

    Just the ATX supplies make great bench test supplies with 3 V, 5 V, +12 V, - 12 V. Just a matter of turning them on out of a computer.
    That has nothing to do with changing the voltage =)

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    Quote Originally Posted by wotnot View Post
    server rack fans spring to mind, beautifully machined & balanced, 3phase brushless motor, screams like a banshee as it pushes huge volumes of air....but all the driver electronics are on the server motherboard, so to use them it's byo ESC and pulse controller.
    This puts me off any server gear at home. The noise those things make is not to be underestimated. Another issue is that enterprise gear has traditionally been designed with scant regard to power efficiency. That aspect of things is changing, but geez... when a mid-range HPE server sucks down 400W at idle (while making an incredible noise), it rules out having this stuff at home. On the bright side, the server power supplies are usually beautifully engineered and designed for very high MTBF.

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    Quote Originally Posted by Hunchback Tech View Post
    Here are a couple photos of just the controller board, as you can see, high density micro SMT.
    This one, I destroyed the V adjust pot for too much soldering resistors. I think it can be repaired (fudged) with a trim pot if only I had schematics.
    Those images have nowhere near the clarity/resolution required to be of any use really, but I can see just enough to suspect all the OCP/OPP/OVP control is defined/implemented as software in the main controller IC.


    Quote Originally Posted by shred View Post
    This puts me off any server gear at home. The noise those things make is not to be underestimated. Another issue is that enterprise gear has traditionally been designed with scant regard to power efficiency. That aspect of things is changing, but geez... when a mid-range HPE server sucks down 400W at idle (while making an incredible noise), it rules out having this stuff at home. On the bright side, the server power supplies are usually beautifully engineered and designed for very high MTBF.
    Yeah, those fans are like living next to a jet engine test cell, and because most of the cabinets are positive air pressure design, so even when the server is doing nothing the fans are spinning fast enough to achieve that pressure displacement, which is typically a few tens of watts per fan even at 'idle' (some of these fans will consume 100watts each at full cry). Indeed, the PSUs in this gear make domestic ATX supplies look like a cheap joke B^)

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    The different manufacturers have these in the IP class, even this obsolete old stuff. Like other old stuff, I was just wondering if documentation has been leaked and hiding on the web somewhere.
    I have an HP 6269A supply, just too damned big for the bench and 94 pounds. Wait til you get a load of the fan noise in this.
    Usually powered a 600 watt HF amplifier or took the place of car batteries.
    So compare here. 10.5 inches long with back plane,1.5 inches high X 3.5 inches wide. Weight just over 4 pounds.
    Output current to 95.6 amp. Not quite double that of the 6269. the fan at max you can hear, but far from any nuisance.
    They are just power supplies, nothing programable. The OVP is its own isolated circuit. Over 13.4 volts, it crowbars and shuts down the supply.
    They are built every bit as well as the 6269, industrial strength.
    I did an RFI test on one and no RFI detected, clean as a pin, makes them great for radio applications.
    They can be paralelled for more current and/or put in series with minor isolation mods. Heard of one power wall at 48 volts and 5000 amps. (more than my Lincoln tig welder)
    Just hoping to glean more info for these supplies.
    73

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    I was just wondering if documentation has been leaked and hiding on the web somewhere.
    Just note that a lot of the time, if there is any documentation out there, it will be listed under it's part number (not brand/model number). Usually it's a had ask because the ODM contracts some OEM company to make parts under a NDA. On top of this, you've only identified 'acbel 550w' & 'liteon 84amp' --- this means nothing, as both TW manufacturers list several design/models under those generalist terms.

    The OVP is its own isolated circuit.
    So to say this with any certainty, you've already reverse engineered this section? Have you drawn a diagram detailing the OVP circuit? (components/values)

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    These are really complicated circuits and different between models and makers. Hard for me with micro SMT and only one poor eye.
    One thing they have in common is a dual op-amp in the voltage control circuit, that gets isolated and fed back to the PWM portion of the supply.
    Over voltage is a bit common, one chip they have in common, just remove and can get 7 to 20 volts. The filter caps are rated for 16 volt so would need changing going over (I call it) 15 volts. Other parts of this circuit are load balancing, standby control, and some have a comms to tell the system all of the supply parameters like fan RPM.
    I will be a while getting something of block or schematics, so far it is mostly voltages and waveform notes. My sacrifice supply I have to clean off the board and to lots of tracing. (multi-layer) and coated.
    A few of the others have been fixed, setting them to 13.21 volts, adding a pre charge switch so the don't fault under load when line applied.
    I'll post some better images a bit later.

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