How to convert a HP HSTNS-PL18 psu to 13.8V ? - Page 1
Forum section: electronics / projects

author: jdev99
author_rank: Regular Contributor
timestamp: October 25, 2019, 09:07:55 am
content: I got hold of a couple of these 750W server psu's , supplying 12V at 62A, and want to adjust it for 13.8V. Do anybody here have any ideas on how to do it?I found a YouTube video which kind of shows how to do it, but the method described does not work.https://youtu.be/4P1-lpzYV1YMine is the same as this one:https://www.parallelminer.com/product/hp-750w-92-efficiency-80-gold-rated-server-power-supply-hstns-pd18-hstns-pl18/

author: jdev99
author_rank: Regular Contributor
timestamp: October 25, 2019, 10:12:37 am
content: I found the solution, after expanding my search criteria.It is in French, but seems to works nevertheless.https://on5vl.org/alimentation-petit-prix/Attached picture is from the website.

author: jdev99
author_rank: Regular Contributor
timestamp: October 25, 2019, 12:40:43 pm
content: I just tested this method on the 460W model HSTNS-PL14, and it works perfect.

author: Pr0metheus
author_rank: Newbie
timestamp: July 20, 2020, 06:29:27 am
content: 13.85 V with HP HSTNS-PL18 psu, works perfectly, thanks!

author: urbanlooney
author_rank: Newbie
timestamp: November 11, 2020, 11:24:21 pm
content: I have been reading the procedure for modifying the HP HSTNS-PL18 from 12v to 13.8v and as I have two of these S/M supplies i am about to do the modification.Before I do, I just wanted to make sure I am reading the mods correctly - I take it that I remove the 100 ohm resistor (near the pot) then put in a hard wire link where the resistor was (bridge out where the resistor was ?), am I correct ?The alternative would be to leave the 100 ohm resistor in place and just bridge it out?Can someone confirm that I am correct as I really dont wish to damage these two supplies.cheers Rob

author: ZigmundRat
author_rank: Regular Contributor
timestamp: November 12, 2020, 03:11:36 am
content: According to the article that’s correct. Bridge the 100 ohm resistor or replace with zero ohm and adjust the pot. I will have to check the lower wattage units to see if they are similar.

author: urbanlooney
author_rank: Newbie
timestamp: November 12, 2020, 06:26:56 am
content: Thank you ZigmundRat I will now go ahead and do the mod on each power supply. I am intending to use the two supplies to give me twin 50amp outputs at 13.8volts to drive radio transceivers and associated gear. cheers.

author: g4jnw
author_rank: Newbie
timestamp: December 24, 2020, 01:49:47 pm
content: I realise this is an oldish thread but maybe someone can answer.I have just got a HP ProLiant 750W PSU Power Supply 506821-001 511778-001 506822-101 HSTNS PL18.I note that the output is 12.1v not quite enough, so was interested in the 13.8v mod.I was also confused by the 2 methods but removing the resistor would be the easiest.I searched youtube and none of the videos showed this method, they only showed adding a resistor and many showed the model as above (with the orange label)What was the outcome of the mod (removing the resistor) did it work and provide the correct voltage, once the pot had been adjusted?

author: ZigmundRat
author_rank: Regular Contributor
timestamp: December 25, 2020, 03:18:31 pm
content: The videos on YT that I saw were for the PD variety of supply, not the PL variety which is described here. The mods are not the same. Maybe double check the model numbers to be sure.The mod described here is changing a resistor to zero value. Whether you do this by replacing it with a zero ohm part or just bridging across it makes no real difference. Unless I missed something, in no case is it described as simply removing a resistor. I suggest that doing so may lead to ‘unpredictable results’... Reread the thread - others have successfully made the mod. Lots of energy in play here, so proceed with care. I hope to get to make the modifications to my supplies during the holiday break, and to check how noisy they are. They are supposed to be pretty good. My Astron switcher sold for ham radio use is not as clean as I would have expected, we’ll see how they compare.Cheers!

author: urbanlooney
author_rank: Newbie
timestamp: February 02, 2021, 07:21:21 am
content: Hi - I have built a dual 13.8vdc power supply using 2 x converted HP modules of this type - they are installed in a metal case, with added switches, LED's, A/V digital readouts, and 50A overloads mounted on the front of the metal cabinet, to drive my amateur radio transceivers.This dual 13.8vdc supply works fine except when the HF transceiver transmits on 40meters and 80Meters the HP modules inside the cabinet shut down immediately, and I have to switch the p/supply mains off and on to get the modules to come back on. I dont have this problem with any other band (10meters - 20meters are perfect even up to 80 watts).The cabinet is earthed separately, there are heaps of ferrite beads and clamp-on ferrites on the cables inside and out, plus a stack of Transorbs inside the supply, but it still shuts down on 40m and 80m.The transceiver is located around 1m from the power supply.Any suggestions ?Thanks, RobPS: I tried transmitting into a 50 ohm dummy load on 40 meters and it worked fine with 70 watts, but unfortunately when I tried 80meters it still shut down the p/supply even with dropping the power down to 10 watts..

author: iMo
author_rank: Super Contributor
timestamp: February 03, 2021, 12:30:44 am
content: What happens when you are running your transceiver from a single supply module only?

author: heytae
author_rank: Newbie
timestamp: July 30, 2021, 04:22:28 pm
content: Quote from: urbanlooney on February 02, 2021, 07:21:21 amHi,I have a similar problem on various HF bands (20m through 80meters) and based on what I've read so far, I THINK it has something to do with the Over Voltage Protection circuit kicking in due to the sudden load changes during transmit. My HF radio needs at least 15 amps transmitting on SSB. Unfortunately, I don't know how to increase the OVP tolerance to resolve this.Has anyone found a solution to this?I've also put an electronic load onto this PSU (which has been modded to put out 13.8v), and the PSU shuts off as soon as the load is gradually increased to 10.5amps, so that doesn't fit the above theory. Maybe there's another root cause.Any suggestion would be greatly appreciated!

author: mojoe
author_rank: Frequent Contributor
timestamp: August 08, 2021, 12:27:41 pm
content: All the mods I have seen on the net talk about increasing the voltage on these. Has anyone explored decreasing the voltage? How low will it go?The mod mentioned here says to short out a 100 Ohm resistor to get up to 13.8V. I assume that inserting a larger resistor would do the opposite? Is it feasable to use a pot in place of the fixed resistor?I ask these questions because I don't have any of these supplies, but am thinking about buying a few.

author: mojoe
author_rank: Frequent Contributor
timestamp: August 08, 2021, 12:39:08 pm
content: I saw a posting elsewhere that said that they found two solutions for this. One was to add some caps on the output. The other was to place a lead-acid battery on the output. Both solutions would provide a buffering action when transmitting.If adding caps, I'd also add a bleeder resistor, or some other way to discharge the caps safely on shutdown.I would be leary of placing a sealed 12V battery directly across the 13.8V output, without also having some type of charge management. An old school flooded lead-acid battery should be more tolerant of this, as long as you monitor your water levels.Not having one of these supplies, I can't say for sure, but there may be a way to mod the OVP circuit to add some delay. If the chips have part numbers on them (not HP specific numbers), a datasheet could be found.

author: rjmusto
author_rank: Contributor
timestamp: October 15, 2021, 02:56:29 pm
content: Hi Guys,I've picked up a few of these PSU's and have done the 'short 100ohm resister' to get the output up to 13.8V.However, I have found on the two done so far that they go unstable (loud buzzing noise and a pronounced ripple on the output at around 1.3kHz) when the load goes above around 10Amps when set to 13.8V. Dropping it to 13.4V and all is ok, I can up the load to well over 20A with no problem.Anybody else seen this? Or any ideas why it's happening. It's hard to believe the control loop goes unstable at just 10A, but maybe.....Thjanks,Ralph

author: magic
author_rank: Super Contributor
timestamp: October 16, 2021, 10:36:32 am
content: Another possibility is some sort of overvoltage protection at the primary, although I think that would more likely shut down the PSU completely until it's power cycled.Any pics or schematics? What sort of controller is there?

author: rjmusto
author_rank: Contributor
timestamp: October 16, 2021, 11:13:45 am
content: Hi and thanks for the reply.I have not been able to find any schematics for these supplies. Lots of YouTube videos showing how to mod them for 13.8V, but not seen anybody then run them hard..... I first thought I just had a faulty one, but when the second did the same, from a differewnt sipplier, different batch, I figured it was a design issue.I'd be much happier if I could find a schematic, don't like doing these 'blind faith' mods.Here's a photo though. The yellow jumper wire is the mod.Ralph

author: magic
author_rank: Super Contributor
timestamp: October 16, 2021, 12:28:37 pm
content: If you look up datasheets of the ICs, they will contain typical application schematics.UC3818 appears to be a PFC controller.UC3895 is a PWM.Not sure what the third one is.I'm suprised to see the PWM on the right side of the isolation gap, does that mean that the PFC is isolated and produces output-ground-referced HV DC which is then stepped down by the PWM?Anyway, it's not entirely a straightforward circuit so modding it will take a few hours of reverse engineering and searching through datasheets and application notes to make sense of the circuit.

author: rjmusto
author_rank: Contributor
timestamp: October 16, 2021, 03:35:20 pm
content: My gut feeling on this was perhaps the same as yours, that some envelope protection was kicking in. Since these supplies are meant to be set to 12v, it's reasonable to assume that overvoltage protection could be set to 14v or 15v and so 13.8v is getting kind of close. The environment they are intended for demands tight controls, so seems a fair assumption.There are 3 other trimmers on the control board. I marked their set positions and then tried tweaking each one in turn to see if I got a change. One of them did. So I can now set the output to 13.8v and go up to over 25A with no issue. Since I could pull over 20A previously with lower voltages, I don't think it is a current sense issue, but a voltage sense one. And this new setting has upped the trip point. Ok, it's a guess, but makes sense (no pun intended).It seems odd that, given the popularity of these supplies in the hobby market, that this behaviour has not been mentioned elsewhere.Anyhow, I'll soak test these two and see how it goes...

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 17, 2021, 05:33:12 am
content: Quote from: rjmusto on October 16, 2021, 11:13:45 amIn the following link and post#1, there is a pdf schematic file of a similar supply PD11, which uses the same PWM UCC3895D controller on the LV side. You can look at it and get some idea of how the voltage and current feedback circuits are connected.https://www.eevblog.com/forum/projects/hp-hstns-pl11-over-voltage-protection-voltage-increase/msg3136804/#msg3136804

author: rjmusto
author_rank: Contributor
timestamp: October 17, 2021, 12:24:05 pm
content: Thanks eblc1388 for that. Really nice to see a schematic.Reading through that other post, it seems my experience with the PL18 is just the same. Staying at 13.4v or lower gives no problems, going higher does.The pot I have tweaked to get rid of the issue for me is shown in the photo. With no values on the schematic and no component designations on the board, it is hard to be sure what I'm looking at. Could it be this pot is VR120? In which case, what is 'IAC Detecting'? (The schematic does not say what IC160 is.)

author: eblc1388
author_rank: Frequent Contributor
timestamp: October 17, 2021, 01:22:33 pm
content: Quote from: rjmusto on October 17, 2021, 12:24:05 pmNo. IC160 is UCC3818, which is responsible for PFC function at the primary side. On the schematic, if you look carefully at the ground pin of that IC, you will see a small letter 'p' inside the triangle symbol. This side is HOT, has no isolation to the mains, means it can electrocute if one touches it.This ground on the low voltage side is a different one, which has a normal ground symbol without 'p'.IAC detecting is the detection of line current signal after the PFC inductor used by IC160 to provide the PFC function.

author: jbuszkie
author_rank: Newbie
timestamp: November 22, 2021, 04:16:09 pm
content: Hello! I've got a bunch of these supplies that I've modded with an external pot to adjust the voltage.I'm using 4 in series to make a 48V charger. I have to keep fiddling with the pots to make the the current "constant".I was hoping to use some digital pots instead to have it be MCU controlled. The problem is the 200ohm digital pot.Has anyone played with other solutions? Maybe a isolated voltage source to fool the feedback pin?

author: serisman
author_rank: Regular Contributor
timestamp: January 23, 2023, 04:46:11 am
content: Sorry for resurrecting an old thread, but I modded an HP HSTNS-PL14 (460W variant) today, and have a few additional details that might help someone else out.So, I traced a few other resistors, and it looks like there are three resistors on the high side of the voltage divider feeding the Vref. One is 4.42k, another is 10 ohm, and another is 39.2 ohm, for a total high side resistance of about 4.4692k. On the low side, there is the 1k resistor, the 100 ohm resistor, and a 100 ohm potentiometer, for a total low side resistance of 1.1 k up to 1.2k. Back calculating gives a plausible 2.5Vref as output of the voltage divider (I could have just measured this in hindsight).So, knowing the Vref, total high side resistance, and low side resistance we can use a calculator to adjust the resistors/potiometer to fit our needs.By default the 1.1k - 1.2k low side resistance gives a (calculated) adjustment range of ~ 11.81V to 12.66V.By bridging the 100 ohm fixed resistor, we change it to 1k - 1.1k for a (calculated) adjustment range of ~12.66V to 13.67V.I went a slightly different route, and replaced the 100 ohm fixed resistor with a 16 ohm, and the 100 ohm potentiometer with a 1k. This gives me 1.016k to 2.016k for a wider (calculated) adjustment range of about 8.04V to 13.5V. I added the 16 ohm to lower my upper bound to about 13.5V since it seems like anything greater might require other mods for stable operation at > 10A.In practice I have also found that anything under about 8.6V isn't very stable, and the power supply shuts down, probably due to an undervoltage condition.After making these changes, I used my load tester and verified that my power supply is stable at 9V up to at least 17A, and at 13.5V up to at least 11A (that is about the limit I can test with my 150W load tester).

author: pienari
author_rank: Regular Contributor
timestamp: May 02, 2023, 06:12:32 pm
content: Hi.Can you upload few pictures of your mod?