Bell and whistles diffusion pump based vacuum system.

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Maciek Szymanski
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Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski »

For some time I’m on the quarantine because my wife has positive covid test (she is ok). To use the time productively I’ve decided to build a complete versatile high vacuum pump system at my garage. I would like to share the building progress and show all the components, as I think it may be beneficial to the newcomers getting into high vacuum world.
The system will be based on the polish Unitra-Unima components. No often to come by outside my country, but for other hand they are quite typical. Almost all the parts I’m using come out of dumpsters at my work (yes, I’ve access to very interesting scientific dumpsters :-)).
The system may look quite complex at first look, and it’s possible to get vacuum without more than half of the hardware I’m using. For other hand this layout is based on the technological setup used in commercial appliances like sputtering systems etc. so it is almost the most flexible and comfortable diffusion pump based system layout.
The main highlights are:
  • It’s possible to vent and pump the chamber many times without need to shut down restart the diffusion pump.
  • The oil back-streaming is minimal.
  • There is no complicated shutdown procedure - just switch off and go home.

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The diagram of the system: 1. Two stage rotary vane pump. 2. Foreline vacuum canister. 3. Oil diffusion pump. 4. Cooled baffle. 5. Diffusion pump isolation gate valve. 6. Chamber pump valve. 7. Diffusion pump forevacumm valve. 8. Chamber vent valve. 9. Foreline isolation valve and rotary pump vent combination valve. 10. Oil trap. 11. DN100 chamber flange. 12. Cooling water circulation pump. 13. Water reservoir. 14. Foreline pirani gauge. 15. Chamber pirani gauge. 16. Bayard–Alpert high vacuum gauge.

The whole system will be mounted on the wooden trolley and any desired chamber can be connected to the CF100 flange at the top (11).
The gate valve (5) allows to isolate the diffusion pump at any time. So it’s possible to vent the chamber at wish with the valve (8) and keep the diff pump running. When the chamber needs to be pumped again the forevacuum valve (7) is closed and chamber pump valve (8) opened to pre-evacuate the chamber. The vacuum canister (2) keeps the back pressure for safe operation of the diffusion pump. As the chamber pressure reaches the desired level the valve (6) is closed and valve (7) opened again. Then the gate valve (5) may be safely opened to pump the chamber to the high vacuum by the diff pump. As the chamber is pre-evacuated by the rotary pump there is no oil vapor burst from the diff pump.
The vacuum canister also simplifies the shutdown procedure - it’s enough to just close all the valves and turn off the heater. The backing vacuum will be held by the canister during the cool down of the boiler. It’s however desired to keep the water circulation to shorten the cool down time.
The combination valve (9) allows to isolate the foreline from the rotary pump (1) and vent the pump itself, to prevent oil flow into the vacuum port.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Dennis P Brown
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Dennis P Brown »

In college, a very long time ago (in a galaxy far, far ... ;) not really) I built an identical system for coating dielectric films as well as metals like Al. Such a system (the ability to seal off the DP and pump the chamber) is very useful and a picture series would be wothwhile as both instruction and general knowledge. I am wondering what type of fittings do you plan on using?
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Maciek Szymanski
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The PDO300 diffusion pump

Post by Maciek Szymanski »

The heart of the system is PDO300 oil diffusion high vacuum pump. This is water cooled, fractioning type pump. The basic specifications are as follows:

Code: Select all

Pumping speed               300 l/s
Ultimate pressure         <10E-6 Tr
Backing pressure limit     2,5E-1 Tr
Heater power               500 W
Oil quantity               100 cm3
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Overall view of the pump: 1. Foreline connection (KF25). 2. Cooling water outlet port. 3. Cooling water inlet port. 4. Inlet flange (CF100). 5. Cooling jacket. 6. Thermal switch (“pump ready” signal). 7. Boiler.

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Heater unit. The heater is put on the bottom of the pump and held with a single central bolt, so the receptacle can be set in any orientation.

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View into the pump’s throat with the jet stack in place. Note the special I13 rings visible in the backing port. Those rings together with the port cooling are the measures to prevent the back-streaming into the foreline.

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All the components of the jet stack disassembled.

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View of the boiler bottom with the jet stack removed.

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View of the jet stack assembled inside the pump body.

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Cross-sectional view of the pump from the user manual. Note the funny detail - the real pump is a “mirror” version compared to the drawing.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Maciek Szymanski
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The OWF300 cooled baffle

Post by Maciek Szymanski »

The OWF300 baffle is designed to be directly bolted to the PDO300 diffusion pump flange. As the pump flange has the rotating retaining ring the pump and baffle orientation can be adjusted as needed.

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The OWF300 cooled baffle. From both sides it has CF100 flange with 8 M8 threaded holes and accepts the standard CF100 centering ring with an o-ring seal.

The baffle consist of two sets of coper deflectors and a coiled tube for cooling water circulation. The deflectors are arranged in a way that there is no direct (“optically clear”) path for the particles passing. So the oil vapor hitting the deflectors is cooled down and condensate. The deflectors of course also affect the pumped gas so the baffle limits the pumping speed to some extent.
This baffle is intended to be water cooled using the pump’s cooling circuit (it should be the firs component the cold water enters), but there are also ones cooled with the liquid nitrogen or a peltier module. But even with moderate water cooling the oil contamination of the chamber side of the system is greatly limited.

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There is no direct path through the baffle. Even despite pumping speed degradation it’s a worth addition to any diffusion pump system.
Last edited by Maciek Szymanski on Mon Oct 26, 2020 3:37 pm, edited 2 times in total.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Maciek Szymanski
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The ZP100ES gate valve

Post by Maciek Szymanski »

The ZP100ES gate valve is the solenoid operated valve which connects to the CF100 flange. The pump side flange has rotating ring so it’s orientation can be adjusted as desired. It has also 4 KF25 ports for foreline and gauge connections. The Choke plate is actuated by the clever kinematic system so it can lift and rotate with a single solenoid pull. In the open position the choke is parallel to the flow direction so almost full 100mm passage is open.

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The ZP100ES valve. The solenoid coil uses 24 V DC to hold, but needs a short pulse of 220 V DC to open.

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Side view. The chamber side KF25 ports are visible.

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View into the open valve. This is view from the chamber side down the diffusion pump. In this orientation when the chamber is vented the atmospheric pressure pushes the choke against the seal, protecting the diffusion pump form leaks.
Last edited by Maciek Szymanski on Mon Oct 26, 2020 9:16 am, edited 1 time in total.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Maciek Szymanski
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The forevacuum distribution

Post by Maciek Szymanski »

As I’ve not found the original Unitra vacuum canister in any dumpster I was forced to build my own:

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The vacuum canister. It’s welded from a piece fo SS tube and standard caps. The flanged port connects to the outlet of the diffusion pump. The two CF25 ports are for the pirani gauge and the control valve.

The two foreline control valves (6. and 7. on the diagram) are of the ZK 25E type. This are plunger 90° solenoid valves. The plunger is gland sealed, but there were also produced “ZWK” valves with bellows sealed plunger. The valves have CF25 fittings and operate with the same combination of 220 and 24 V DC as gate valve.

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The ZW 25 Valve. There is KF25 centering ring with seal and KF25 clamp for connections. As well a bellows compensator.

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The vent valve. It’s a small plunger type valve with a mesh filter. The solenoid is operated by 220V AC.
Last edited by Maciek Szymanski on Mon Oct 26, 2020 9:07 am, edited 1 time in total.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Maciek Szymanski
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The assembled high vacuum part of the system.

Post by Maciek Szymanski »

The whole high-vacuum part is now assembled on the cart.

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The cart with the opening for the chamber CF100 flange. The lower shelf will hold the rotary pump and cooling water tank.

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The high vacuum assembly. Items as on the diagram: 2. Foreline vacuum canister. 3. Oil diffusion pump. 4. Cooled baffle. 5. Diffusion pump isolation gate valve. 6. Chamber pump valve. 7. Diffusion pump forevacumm valve. 8. Chamber vent valve.

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“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Richard Hull
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull »

Great start on a superb vacuum system. Thank you for sharing your progress as you build the system. A very clean looking diffusion pump. All good vacuum systems make use of numerous valves. I consider a minimum of 2 bellows valves are needed on any fusor system. 3 such valves would be better. Unfortunately, such valves are expensive and hard to come by, surplus, in good shape for the average vacuum system neophyte.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Artem Artemov
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Artem Artemov »

It reminded me of the Soviet VUP-5 installation. With this installation, my acquaintance with vacuum technology began. But I noticed that the entire structure is attached to OSB (perhaps you have this material called differently). I don't see any metal stiffeners. Will it support a lot of weight? OSB may be stratified due to the high temperature of the diffusion pump!
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Maciek Szymanski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski »

Very nice setup. I like the chamber design. The electronic unit on top is a pump system controller or a part of the process equipment? The original Unitra system looks like this:

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And yes, the shelf’s are made of 18mm OSB, but they are reinforced with frames of 20x40mm pine wood. It withstand my weight without any visible defection. And the only hot part is the heater and boiler - the parts connected to the board are cooled.

BTW - I’ve got a very nice Soviet made diff pump baffle cooled with peltier module. The pity is that the flange do not fit the polish equipment and the peltier requires more than 20 amps. So it nods some machining and a decent buck converter PSU.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull »

Varying odd ball OEM flanges and multiple "in country standards" will forever seem to force a lot of less well equipped amateur scientists with limited funds to adapt pieces of vacuum gear to mate with other surplus vacuum items. There are many good deals to be had surplus on the market. However, with no machining or welding skills, the average amateur is forced to pay machine shops to do what they cannot. This can sour a good deal bought for a great price to the point that it is no longer such a good deal. The two type flange adapters of more or less different, yet, "standard flanges", can solve some issues, but the adapters can cost a good bit of cash, themselves. This is most unfortunate for the more impoverished and unskilled young vacuum system assembler.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Dennis P Brown
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Dennis P Brown »

As a physics major in college (again, long ago), I was expected to go to the main machine shop and get guidence on machining the base plate and adapters for experimential equipment I needed.
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Wiring the control panel

Post by Maciek Szymanski »

I’d like to have a fully manual control panel for the system. The panel will serve also as the switchboard for other equipment. All the component come or either from a dumpster or are bought cheaply from the army surplus. The most expensive part was the textolite board on which the whole thing is assembled.

Artem Artemow I think you should like the style ;-)

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The control panel installed on the trolley. The big rotary switch is the main isolation switch. Below are the fuses and main pilot lamp. The row of small rocker switches controls all the solenoid valves valves and the water circulation pump. Pilot lamps below the switches indicate the operation of valves equipped with position contacts. The big 3 phase switch with removed housing is for rotary vane pump and the rotary switch right to it is for the diffusion pump. The four mains sockets are for vacuum gauges and other experiment related equipment. The four pole socket is for rotary dump. Still not installed are multi pole sockets for valves.

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Wiring the panel on the backside.

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The 3 phase motor switch with electromagnetic overload protection.

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Machining of the capacitor bracket. For the solenoid valves there must be a supply of 220V pulste to activate the valve. This will be done by a bank of electrolytic capacitors charged to 220V when the valves are closed. This small textilste bridge will hold them on the backside of the panel.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Dennis P Brown »

Talk about 'classic' controls! Right out of a 1930's Sci-Fi movie. Nice. While I used relays and push buttons in my orginal, there is something both 'classic build' and pleasent aspect to a control pannel with those manual controls (and just like in in Star Treck, going to "manual override" which their last effort against the computers, you can too ... ;) )
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Artem Artemov
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Artem Artemov »

A lot of retro. Haven't seen these things in a while.

The three-phase switch is very similar to the Soviet АП50Б. It was given to me when I was a child. All these parts have a huge margin of reliability. The Chinese switches I want to use can't boast of this. Not enough big arrow meters! )
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Maciek Szymanski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski »

The switch is indeed Soviet production АП50. As for the needle meters - they will come with the vacuum metering system and the HV supplies.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski »

The panel wiring is finished. Today I’ve tested some valves.


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Re: Bell and whistles diffusion pump based vacuum system.

Post by Dennis P Brown »

Proffesional wiring work; pictures appear very circa 1950's! Especially that type of wiring in your earlier color pic of a panel. The black and white pic's really adds to that sense. Today seems like through back Friday on posts.
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull »

The cable lacing is a very military WWII touch. Today, coiled plastic tube seathing is used or nylon zip ties. Nice work.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski »

I’ve finally come back to my vacuum system.

I’ve installed the rotary vacuum pump:

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Unitra BL8 rotary vane pump. This is two stage oil rotary vane pump with the gas ballast valve. It is belt driven by 3 phase motor. On the vacuum port of the pump there is installed the oil trap ant the manual isolation/vent valve. According to the catalogue the pumping speed is 6,7 m3/s at 1 Torr and the ultimate pressure 5e-4 Torr

The control panel is finished, with sockets for the control valves and the 24V transformer:
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The water cooling hoses and the coolant tank for the diffusion pump:
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As the low vacuum metering system I’m using Unitra PN21 double channel analogue pirani gauge. The unit was overhauled and calibrated with a good Leybold metering system at my work. Here is the control unit, the pirani head and connecting cable. The small cover on the right side of the instrument covers the calibration potentiometers.
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Today I’ve pumped the system with the rotary pump only. There was no chamber - the system was closed at the gate valve CF100 port with a reduction ring and a viewport. So the pumped volume included the diff pump, the cooled baffle, the gate valve body, , the vacuum canister, control valves, and the rubber vacuum hose. I was able to get it down below 25 microns in about 15 minutes:
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I’m quite happy with it, especially that I’ve not changed the vacuum pump oil - I want to run it some time with the old oil before I replace it, as the pump was quite long in the storage. I hope for better figures with new oil. The control system need some minor improvements, like adding an extra pulse capacitor for the gate valve - the current one is on the limit, an sometimes the valve fails to open.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull »

I have always recommended running with old oil in a pump, (provided a small drained cup full is not just dark gummy soup). The old oil, if it has covered things up well should be run for over an hour until the pump is hot. In this manner all the seals and walls will have a chance to circulate and get any crud and glop off the walls and partially polish the vanes and their springs. If what comes out is nasty then you have done good and will not totally waste a first run of clean oil. If what comes out is relatively dark but clean then so much the better.

Your first run with old oil from storage was really quite good! Fresh oil may win you a clean and nice running pump. Great work on the foreline pump setup.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski »

Today I’ve made some minor improvements to the system - I’m hoping to test the diffusion pump tomorrow. But for today I’ve celebrated by making a little bit of plasma:


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Re: Bell and whistles diffusion pump based vacuum system.

Post by Richard Hull »

Please run the plasma again. Report the voltage, the pressure and the current and you will be the first human being to make the new plasma club!! The rules say to must report those three variables. You have already supplied the required images. Fabulous images!

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Maciek Szymanski
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Re: Bell and whistles diffusion pump based vacuum system.

Post by Maciek Szymanski »

Richard! I don’t think it’s worth the plasma club - I’ve done it mainly to test the micrometric valve I’ve rebuilt some time ago. Ad as I had In hand a random feed through and a power supply from an ancient photocopier (5kV and very current limited due to selenium rectifier stack based voltage doubler) I just put a soft soldered “grid” inside to make nice plasma photos.
I’m building much more serious power supply based on the breakdown tester transformer. Then I’m going to do some experiments with electron current measurements.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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Maciek Szymanski
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Those damn switches

Post by Maciek Szymanski »

For controlling the solenoid valves I’ve used old Russian ТП1-2 rocker switches. They are rated 2 amps. But apparently the transient currents of those big electromagnets overloaded them, and two has failed. Today I’ve replaced the three switches with standard Chinese ones - 10 amps rated. Two failed immediately. Third failed after one successful switching.
I hope that the 5A rated Russian switches will be reliable enough...
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.” ― Lewis Carroll, Alice in Wonderland
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