3.5kV power supply teardown - Page 1
Forum section: electronics / testgear

author: rolycat
author_rank: Super Contributor
timestamp: November 13, 2013, 02:49:54 pm
content: I recently acquired a Pharmacia Biotech EPS 3500 XL power supply for 'next to nix' and thought a mini-teardown might be of interest.It can generate up to 3500V at 100W and monitor the current to within a microamp. Unfortunately the shrouded 2mm connectors for the outputs are expensive unobtainium, so I haven't (yet) been brave enough to run it up to its full capacity. Fortunately some multimeter probes reach nicely, so its good up to 1000V.The instrument was designed and built in Sweden and dates from the mid nineties. Apparently it was designed principally for 2D electrophoresis using isoelectric focusing.I also have an EPS 300 from the same manufacturer. With a 300V maximum output it is rather less exotic, although I could probably do a teardown if anyone is interested.Here is the EPS 3500 XL feeding 1000V to a multimeter. Meter input impedance is 10 megohms, so the 100uA measured draw is spot on:The back of the unit. The fan is a Panaflo FBA08A12W, curiously the exact model used on an HP E3631A PSU which I am currently attempting to repair:The main PCB, proudly designed by Kenneth Lindh. The large power MOSFET at the back is a 2SK1359:And the backside, with some appropriately tall standoffs:The processor, a Hitachi (now Renesas) H8/532. The 8 pin chip is a TL7705ACP voltage supervisor. Other ICs on the board are the firmware ROM, an LT1244 switching controller, an LM339 comparator and two TL074 op amps:The voltage multiplier section. The diodes are BYV26E 1000V ultra fast avalanche types. Electrolytics are all Nichicon 400V 10uF:The final output stage, linking -1750 and +1750 volt sections with a 4kV 3n3 ceramic. The wires to the output terminals with the ferrite beads attached are stiff and somewhat springy:

author: rsjsouza
author_rank: Super Contributor
timestamp: November 13, 2013, 03:23:55 pm
content: Thank you for the teardown. I have a special attraction to high voltage design, and this one is really nice.BTW, you have a nice probe insulation tester in your hands... Simply grab some el-cheapo probes and start increasing the voltage to check their insulation... I have not seen any probes to fully break through the insulator (even some terribly cheap ones), but you can see the glow around them in a dark room...

author: PedroDaGr8
author_rank: Super Contributor
timestamp: November 13, 2013, 05:18:01 pm
content: NIce, this is a high voltage gel electrophoresis power supply (considering the voltage it might even be used for capillary electrophoresis as 3.5kV is too high for most gels).A bit about the company. Pharmacia is famous for making the Äkta brand of FPLC machines. If you have worked in a biological lab where you purify biological compounds you know about Äkta's. Pharmacia was acquired by Amersham Biosciences which was subsequently acquired by GE Healthcare Life Sciences. I have an old board out of a Pharmacia Äkta. It shares a lot of the same parts with this one (minus the high voltage rated ones). The blue box caps, the whole power switch, power input and connector next to it, the microcontroller, etc. are the same.

author: TerraHertz
author_rank: Super Contributor
timestamp: November 13, 2013, 05:51:51 pm
content: Nice looking board. You don't happen to have a schematic?It is quite amusing that the 'STOP' button is closest to the output terminals. Sort of 'I *dare* you to stop me!'You should be able to improvise a shrouded connector using some PVC tubing of appropriate size, bits of wire, gold-plated pins from D25 connectors, and silicone glue?

author: nathanpc
author_rank: Unknown
timestamp: November 13, 2013, 05:57:20 pm
content: "Made in Sweden"That's something you don't see very often.

author: rolycat
author_rank: Super Contributor
timestamp: November 13, 2013, 10:12:54 pm
content: Quote from: PedroDaGr8 on November 13, 2013, 05:18:01 pmYes, as I mentioned in the intro it is primarily intended for two-dimensional gel electrophoresis. This uses 2 phases, one using isoelectric focusing across a pH gradient to separate the proteins by their isoelectric point, followed by a second phase at 90 degrees to the first, which sorts by molecular weight.As a consequence, the power supply can be programmed to run up to nine separate phases with different voltage/current/power profiles.Quote from: TerraHertz on November 13, 2013, 05:51:51 pmAlas, no. I would be very happy if anyone knows where I might find one.QuoteMaybe. The 2mm socket is drilled into a protruding brass post which is buried over 20mm deep in the outer socket:Making a reliable and safe connector will be a challenge...

author: PedroDaGr8
author_rank: Super Contributor
timestamp: November 13, 2013, 10:24:51 pm
content: Quote from: rolycat on November 13, 2013, 10:12:54 pmI completely missed that partYeah, one of my co-workers has been doing a large number of IEF gels to resolve some antibody stability issues though our gelsonly require around 600V (then again we aren't doing 2D only 1D).

author: robert555
author_rank: Newbie
timestamp: November 14, 2013, 12:55:16 am
content: Made in Sweden, yey!Nice teardown, i like high voltage stuff!

author: samofab
author_rank: Regular Contributor
timestamp: November 14, 2013, 07:17:56 pm
content: If you plan to modify the connectors on the front, I recommend replacing them with MHV connector (looks like BNC, but it's good up to 5kV & 3A).

author: Monkeh
author_rank: Super Contributor
timestamp: November 14, 2013, 07:31:26 pm
content: I was watching that very auction. Looks like a really nice piece of kit.

author: LaurenceW
author_rank: Frequent Contributor
timestamp: May 28, 2014, 07:39:04 pm
content: Hello Rolycat,I have just scored one of these power supplies on Fleabay. I am looking to use it as a general purpose HT voltage supply. I can see that I am going to have to <ahem> modify one of the safety features - namely its ability to detect ground currents and shut down. Did you ever get hold of a schematic for this or any similar designed units?

author: tom66
author_rank: Super Contributor
timestamp: May 28, 2014, 08:48:03 pm
content: How does it sense output voltage and load current?

author: rolycat
author_rank: Super Contributor
timestamp: May 28, 2014, 09:56:30 pm
content: Quote from: LaurenceW on May 28, 2014, 07:39:04 pmAfraid not - and it was permanently shut down for a few months because the IEC inlet/filter exploded and chucked its guts all over the PCB:Of course, the unit was switched off at the time, so when I went into my lab to be greeted with a nasty stench it took a while to figure out what had caused it. You may want to keep yours unplugged or switched off at the wall when not in use.I have recently installed a replacement inlet/filter, and it's running again. Very handy bit of kit when you need some serious volts, but as you say the circuit is very safety-conscious.

author: tautech
author_rank: Super Contributor
timestamp: May 28, 2014, 10:05:22 pm
content: That's never a pleasant sight.Being a switchmode supply, you would be wise to check the E-caps for signs of degradation.Or maybe it was just a case of the mains input filter doing its job?

author: ve7xen
author_rank: Super Contributor
timestamp: May 28, 2014, 10:10:03 pm
content: I believe Schaffner inlet filters from the 90s have a history of doing this, it plagues test equipment too. If you replace it, don't use NOS, is the general advice.Thanks for the interesting teardown. Surprising that the board doesn't like *all that* different from a low voltage one, was expecting more obvious attention to isolation (though I'm sure it's well designed it just doesn't show).Dave did a teardown of another electrophoresis supply a while ago, if you haven't seen it:

author: rolycat
author_rank: Super Contributor
timestamp: May 28, 2014, 11:16:55 pm
content: Quote from: ve7xen on May 28, 2014, 10:10:03 pmYes, I contacted Schaffner and they recommend the current model FN9226-3-02 as a replacement. It's missing the plastic flanges around the screwholes, but should fit OK. It was pricey though, so in the event I used another brand of filter which happened to fit pretty well.QuoteI did watch that, thanks. An interesting teardown as always, but I wasn't very impressed with the EC250-90 - the general design and regulation seemed more primitive than the Pharmacia models I've seen.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 29, 2014, 01:59:16 pm
content: Interesting to see those blue 47nF capacitors in the voltage multiplier section. ( I think they are also made in Sweden but I forgot the name)And then see the German made WIMA at the output stage.I remember the days, when we opened anything of quality and it was full with red and yellow WIMA capacitors.These days, you really have to look for them.Also the high voltage diodes look like they are of high quality, may be Vishay or so.It would be really nice to look at a schematics for this instrument.May be the layout is so nice, because it was for medical applications and money did not matter too much.Any Idea how much this unit was, when it was brand new?Thanks for these nice tear down pictures, I really enjoyed looking at them.

author: rolycat
author_rank: Super Contributor
timestamp: May 29, 2014, 06:08:05 pm
content: Quote from: tom66 on May 28, 2014, 08:48:03 pmGood question. The only tap I can see from the output stage is two high voltage 10M resistors in series lurking under the output terminals. They connect to the positive output at one end and two of the non-inverting inputs of a TL074 quad op-amp at the other.

author: rolycat
author_rank: Super Contributor
timestamp: May 30, 2014, 02:26:30 am
content: Quote from: HighVoltage on May 29, 2014, 01:59:16 pmRifa:Since swallowed by the Kemet Corporation. The large blue 470n X2 capacitors and the white 2n2 Y2 caps in the mains input stage were also made by Rifa.The transformers are also Swedish - the control section supply transformer was made by Transformator-Teknik AB of Åmål, Sweden.(Incidentally the town is famous; there's an eponymous film with a very controversial title.)QuoteIt's still a current model, cosmetically tweaked as the EPS 3501 XL. These are quoted by GE Healthcare, (who bought Amersham Lifesciences, who bought Pharmacia), at $4,971.QuoteMy pleasure.

author: HighVoltage
author_rank: Super Contributor
timestamp: May 30, 2014, 11:05:34 am
content: Yes, RIFA, that was the name... ... we used them in the 1980th a lot in projects in Sweden.I was so much intrigued by your teardown, I found a EPS 3501 XL in like new condition and just bought it. It should be here in a week or so. Then I will open it up and see, if there are any visible differences. Thanks for your inspiration.

author: Lodoiska
author_rank: Newbie
timestamp: April 22, 2018, 05:02:06 pm
content: Hi!I know this is an old thread, but just in case some of you are still here... Has anyone tried this power supply with non-sheated 2mm plugs? I also got one, but as it has been specified, the connectors for this are really expensive, when you can find them at all. So I was wondering if someone had tested it successfully with normal 2mm plugs, without bypassing the built-in securities?Thank you!Lodo

author: Yansi
author_rank: Super Contributor
timestamp: April 22, 2018, 06:37:42 pm
content: Quote from: HighVoltage on May 29, 2014, 01:59:16 pmThese days you get a lot of red low spec caps from Wurth instead

author: HighVoltage
author_rank: Super Contributor
timestamp: April 22, 2018, 07:44:20 pm
content: Quote from: Lodoiska on April 22, 2018, 05:02:06 pmHello Lodoiska and welcome to the forum.I have made my own connectors with gold plated MultiContact 2mm banana plugs for the EPS 3501 XL.It works really well, is safe to use and no security issues at all.

author: Lodoiska
author_rank: Newbie
timestamp: April 23, 2018, 02:50:35 am
content: Hi!Thank you and than you!You have no idea how much your original post has helped me; I was going mad looking for info on this power supply's connectors. Not even in the manual do they specify what is required!! You were the only one to specify it. And I am lucky you still are a memberSo, if I understand well, a (quality) non-sheath 2mm banana plug will work? Because a 2mm male to 4mm female can be found easily, and the electrophoresis cables available in my lab are with the new 4mm sheath standard. That would be so much more simpler and economic than finding the right "science" adapter...(yup, I am that weird, I am going to use this for what it was originally meant... ;P )Thank you so much,Lodo

author: HighVoltage
author_rank: Super Contributor
timestamp: April 23, 2018, 08:59:35 am
content: I am traveling right now til the weekend.Then I can upload some pictures if you want.No, do not use 2 to 4 mm adapter, that is not safe !!!I used gold plated 2 mm straight banana plugs and made myself someholders / spacers out of teflon (PTFE)On one side of the holder the 2mm banana plug comes outOn the other side a good quality high voltage cable comes outI have no idea how the original cable and plug looks like but the one I built is perfect for my needsand 100% safe!

author: Lodoiska
author_rank: Newbie
timestamp: April 23, 2018, 12:24:10 pm
content: Hi!If you woudn't mind, I would greatly appreciate it!!Thank you so much.Safe travels,Lodo

author: Diplomata
author_rank: Newbie
timestamp: October 12, 2018, 03:13:03 pm
content: HelloDo you know who the manufacturer of the power supply enclosure is?Or does anyone know who is the manufacturer of Pharmacia AKTA system housings?I can only realize that they are made of cast aluminum / magnesium ...And it should be a northern European manufacturer, since it was of Swedish construction. Thank you.Best regardsCarlos Barata

author: coromonadalix
author_rank: Super Contributor
timestamp: October 12, 2018, 10:46:17 pm
content: They are beautifuldrool

author: klim
author_rank: Newbie
timestamp: June 15, 2020, 08:14:40 am
content: Hi, could you please upload a picture from your plug connectors for this device, i'll get mine next week, but also without any connection plugs, so i need to make my own.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 12, 2020, 04:44:05 pm
content: Just saw your post now...First I used self constructed 2mm connectors.But at the end I did not like them too much.Then I rebuilt the connector completely for 4mm banana plugsFor up to 1000 Volts I am using the MC insulated cables.For 1000 to 3500 Volts I am using my self made 20.000 Volts cables to 4 mm banana plugs.Here are some pictures of my setup.

author: Gulftown
author_rank: Regular Contributor
timestamp: January 15, 2024, 10:16:37 pm
content: Quote from: rolycat on November 13, 2013, 02:49:54 pmI just repaired my EPS 3501 XL, which i bought cheap as party only on ebay, based on your photos.Thanks a lot!I guess it had a broken free run diode at the large power mosfet, which killed the mosfet and through this the 6 times 1 Ohm shunt resistors, 27 Ohm gate resistor and the LT1241. I had i hard time figuring out what the problem was. Includuing a lot of broken power mosfets.But in the end replacing those components did the trick.

author: coppice
author_rank: Super Contributor
timestamp: January 15, 2024, 10:24:55 pm
content: Is this the kind of 2mm shrouded plug you need?https://warwickts.com/4655/PJP-226-IEC-2mm-Stacking-Shrouded-Banana-Plug. I bought some of these to use with my Voltech power analyser, and they work OK for that. They are not rated for 3.5kV, but plugs like this generally work OK to many times their rating.

author: HighVoltage
author_rank: Super Contributor
timestamp: January 16, 2024, 09:40:23 am
content: Quote from: Gulftown on January 15, 2024, 10:16:37 pmNice repair, even without a schematics, these power supplies can be repaired kind of easily.I bought a couple more and all they had were loose solder connections from heavy parts.

author: Hydron
author_rank: Super Contributor
timestamp: January 16, 2024, 10:19:36 am
content: How annoying are the "safety" mechanisms on these (e.g. ground leakage, minimum load requirement etc)? And are they easily defeated? I previously had a different unit which ended up in the too-hard pile and eventually got parted out, as it was very fussy about loading and had other issues (massive overshoot) as well which made it pointless to spend the time on.

author: Gulftown
author_rank: Regular Contributor
timestamp: January 18, 2024, 02:25:09 pm
content: Here is my not-so-nice-looking reverse engineering attempt to the hv power supply secion of my EPS3501 XL.But maybe it helps someone.So you can disable the load check and i used normal multimeter probes for testing up to 3.5kV, you shouldnt be anywhere near the device with those probes, but it did not cut the power.I tested a 100W incandescent light as a load at 230V with no problems.The output voltage is 0.1% too high with my unit, and the constant current mode is a little bit unstable at +-1mA but the readback seems fine.Its relatively slow in ramping up, needing about 6-10 seconds to reach the target voltage and the HV LED is shutting off instantly after disableing the output, but the output caps are still charged for about 30 seconds.I desiged a HV detector board which overwrites the led as long as the caps are loaded above 40V so its safer to use for me.I will post it, as soon as i had the chance to test it.I am planning to change the binding post to normal 4mm banana plugs, because i will never need the 3.5kV capability anyways.I will mainly use it to test old caps for leakage and as B+ for tube amp projects at maximum 680VDC

author: Gulftown
author_rank: Regular Contributor
timestamp: January 18, 2024, 04:14:07 pm
content: Quote from: coppice on January 15, 2024, 10:24:55 pmNo i dont think, that would fit.The original sockets are very deep, and there is just a 2mm wide hollow screw at the end as a socket.These are the original plugs, but they are very hard to find. So im swapping the sockets.

author: Gulftown
author_rank: Regular Contributor
timestamp: January 19, 2024, 12:24:30 pm
content: So i replaced the binding posts with recessed 4mm banana sockets.It works very well and the mod is easy and fully reversible.The sockets are Stäubli SLB4-F6,3/N-X.I attached the STL.

author: Gulftown
author_rank: Regular Contributor
timestamp: February 04, 2024, 08:07:47 pm
content: I finished the design of the HV detector mod.It has up to 10G Ohm input resistance, but i use it with 6GOhm and it does not affect the current measurement.The LED changes from green to red, as soon as the output is >25V (adjustable).It stays red as long as there is voltage above the threshold on the output.The EPS3501 XL is actually a + and - 1750V supply, thats why i use 6GOhm input resistace.It works very well and will definitely improve the safety of the power supply.https://oshwlab.com/marius.meiswinkel/hv-sense-circuitPCB Files

author: patrpl
author_rank: Newbie
timestamp: April 01, 2024, 01:15:02 pm
content: Hi,I have a Pharmacia Biotech EPS 3500 in my lab that isn't working because it's missing some pieces just like the ones in the photo.Can anyone help me by telling me if I can buy these pieces separately and where I can buy them online?Thanks.

author: Gulftown
author_rank: Regular Contributor
timestamp: April 19, 2024, 04:23:16 pm
content: That looks like a part of the output plug?I swapped them to standard 4 mm banana jacks.Except for the binding posts, you can buy more or less any electrical replacement part for this supply at mouser or digikey.