3.5kV power supply teardown

[Lodoiska]

Hi!
If you woudn't mind, I would greatly appreciate it!!
Thank you so much.

Safe travels,
Lodo

[Diplomata]

Hello

Do 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 regards

Carlos Barata

[coromonadalix]

They are beautiful   drool

[klim]

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.

[HighVoltage]

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 plugs

For 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.

[Gulftown]

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:

I 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.

[coppice]

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.

[HighVoltage]

But in the end replacing those components did the trick.

Nice 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.

[Hydron]

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.

[Gulftown]

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

[Gulftown]

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.

No 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.

[Gulftown]

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.

[Gulftown]

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-circuit
PCB Files

[patrpl]

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.

[Gulftown]

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.