Turbomolecular pump troubleshooting (EXT255H with EXDC80)

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Arun Luthra
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

I acquired a second EXDC80 and everything is much the same.

When off, the start pin 1 reads 6.5V relative to 0V on the supply. According to the manual, it should be 4 to 24 V d.c., so it is within range...

I have a DC power supply connected to a voltage booster. The DC supply is supplying 30V and reports 0.22 amps. The 80V output on the booster is pulling 1.0 Amp.

I close the start pin to the 0V on the power supply.

My 30V power supply has +, -, and ground. I connect this ground to the ground on the pump, and the ground pin on the EXDC80 (pin 3).

I don't have an oscilloscope, but the DC supply has no change at all when I switch from off (open) to on (closed).
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

If the DC power supply is at 30V and 0.22 amps, that is 6.6 Watts.

I don't understand why the 80V is at 1.0 amps. That is 80W, which is supposed to be the full current load when the pump is on. I measured this by putting the meter
leads on the + and - terminals of the 80V DC booster. This is incompatible with the 30V/0.22A displayed on the DC power supply.

Meanwhile, the 6.5V on the start pin times 1.0 amps is 6.5 Watts??
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Chris Giles »

Hi Arun

are all of those figures measurements or programming settings? With power supplies that allow you to set the current and voltage they can run in constant voltage or constant current mode and this may not be obvious. The settings work as limits, i.e.:
- if you set the current at a value lower than your load will consume at the voltage setting, then the PSU will reduce the voltage until the current does not exceed the setting - this is CC mode
- if the voltage is not limited by the above then it will be set to the voltage setting - this is CV mode.
Your PSU may display the limits rather than the actual values. If you are not sure, then experiment with a resistive load and measure the current and voltage independently with a DMM then try to alter the settings. Be careful not to exceed the current which your DMM can handle.

Example: with 100R, 1W resistor @ V = 10V:
- it will be in CV mode if I set @ > 0.1A
- it will be in CC mode if I set @ <= 0.1A, then you will see the actual voltage dropping below 10V

Specifically, given what you said above, is the 1.0A current on the 80V output a setting or measured using a DMM in series with the load (Turbo PSU) at the same time as measuring the voltage across the load (80V?) ?

regards
Chris.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

I got ANOTHER pump and it is showing the SAME problem. Either my DC power supply is not working, or the DC booster, or (most likely) my wiring or configuration is wrong.

The DC power supply says CV mode, it displays 30V and 0.22A, with the switch off. I measure 0.35A across the + and - leads of the DC power supply.

The current limiter knob on the DC power supply is fully clockwise to allow maximum current.

I measure 80V and 0.98A across the + and - leads of the output of the DC booster. I measure 0.98A across the pump load with the switch off, and switch on.

There is 4.0V between the start pin 1 and the ground of the power supply. There is 6.67V between start pin 1 and the - on the booster.
tmp-1.jpg
tmp-2.jpg
tmp-3.jpg
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by John Futter »

arun
your power supply is one of those super cheap chinese switchers
we bought one at work thankfully it blew up but it did not like talking to another switch mode down stream (in this case your upconvertor)
use a linear bench supply --there is no substitute in a home lab --those switchers cause more problems than they fix
also put a capacitor on the output of your up convertor to stop it from going into current limit when you start the pump around 10,000uf would be good
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Richard Hull »

I was about to suggest a real "man's" power supply. Gotta' put a 160 watt load at 80 volts in the form of a 40 ohm 300 watt wire wound. Now that is a real supply if it still reads 80 volts across the 40 ohm resistor. Sure you don't need that, but that is the kind of supply and the kind of real test you need to perform. Then you have a man's supply.

Richard Hull
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Cristiano_Machado »

Hello,

I have one EXT255H, but my controller is EXDC160. I found an old post about the controller and it seems that the manual you are using is for the new model.

My model was an old one, and the post recommended the attached manual. It worked perfectly for my turbo and controller. I use just a 24V power source.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

The manual I posted is for EXDC80, part number D396-40-000. This matches the part number and description of the physical unit, and it takes 80V. It has a 9 pin connector.

There are also 24V pumps, and 24V EXDC drive modules, called "EXDC80 24V" etc, which sounds like your system.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Rex Allers »

Arun,

Maybe I'm not understanding what you describe, but what you said about measuring current makes no sense to me.

You said,
"I measure 0.35A across the + and - leads of the DC power supply."
and
"I measure 80V and 0.98A across the + and - leads of the output of the DC booster."

Are you saying you have an ammeter or a meter set to amps and you are putting the probes across the + and - terminals of your supply and also + and - of the booster output. If so, I don't know why that didn't blow a fuse in the meter or read a lot higher.

An ammeter needs to be in series between one side of the supply and its load. It measures the current flowing in the circuit by having that current pass through the meter on its way to the load. An ammeter has effectively (close to) 0 ohms between its terminals. If you connect it across the output terminals of the supply, you are measuring all the current the supply can give. With a decent supply that may be more than the meter can handle and usually there is a fuse in the meter that will blow.

You said the main supply can make 30V at 5A. If you have it set to 30 V and the current knob is all the way up, then you put an ammeter across the output terminals, the ammeter should read about 5A (unless that's too much for the meter and it blows the meter fuse). While making 5A, the voltage on the supply's meter should drop down near zero.

Does that make sense to you? Did I misunderstand what you did in measuring the current?

Something in your description and/or what you measured doesn't make sense at the level of ohm's and Kirchhoff's laws.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

Good point. My meter has some kind of short circuit protection, so maybe that was triggered and the value it was reporting was junk.

I have a linear bench DC supply arriving tomorrow.

When I set the meter to max/min mode and measure the voltage on the 80V DC booster when I turn on the 30V switching supply, it reports "OL" meaning over range, however I need to redo this to make sure it is measuring an appropriate voltage range. It is set to autorange on voltage, but maybe autorange does not work in max/min mode. Hopefully it is truly doing a voltage spike on startup which is triggering the pump to go into fault mode, because otherwise I don't know what the problem is.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Chris Giles »

Hi Arun,

I recommend that you get comfortable with how to measure voltage and current first and experiment with how the voltage and current limit settings work on your PSU(s). You can do this by using some resistors and experimenting with the PSU at low power, say < 10V and < 0.5A. This will be useful for you for other tasks as well.

As Rex points out, if you have put the meter *across* the PSU while measuring current, you have short circuited it! Whilst this will indeed test the current limit it is highly inadvisable especially with a cheap PSU and above a few volts. I don't think you will get any useful information using the DMM in min/max mode. To see the dynamic behaviour one would use a scope but that should not be necessary for this task.

If you tried the Turbo when the PSU was not shorted out, then I suspect that you have not satisfied whatever conditions are necessary to enable the motor drive. Your other measurements make it seem like it is in a standby state.

Regards
Chris
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

The linear DC supply arrived, but the problem remains. Everything is the same.

I will try the 10,000 uF, 100V-rated capacitor when it arrives in 48 hours.

In the meantime, I'll investigate potential issues like oil level.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Cristiano_Machado »

Hi Arun,

Can you explain how you are wiring the driver? Are you sure you are using the right pins with the correct input?
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

Here is the pinout that I'm doing:
pins-labeled.jpg
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

I'm pretty sure it's correct, but hopefully is something is wrong and it can be easily corrected.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Cristiano_Machado »

I may be wrong, but it seems that you have a problem on pin 2. I am not an expert, but I believe you should connect pin 2 to pin 5 and 6 (0V).
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Rex Allers »

Re pin 2:
Pin 2 should be an output (80% speed) which should not be needed, especially since he can't yet get the turbo spinning. Definitely, don't connect it to ground.

From the manual he linked, here is the pin-out description.

EXDC80 pins.png
I had looked at his earlier pics and thought the connections looked OK. The new closer detail pic seems to confirm.

As Arun said, the EXDC80 has a nine-pin connector. The other hook-up suggestion was for a 15-pin connector that seems to be for a different driver module.

Arun,

You never said anything about this new supply except that it is a linear bench supply. What is it? What voltage and current ratings? Is it still the input to your 80V booster card or does it make the 80V directly?

You never really seemed to indicate that you understood what we were saying about how to measure current.

For diagnosis, I hope you have or can get two meters to connect at the same time. One to measure voltage and one for current. Hook them up as in this diagram.

measure.png
Note that the amp meter is on a single wire between the supply (+) output and the driver input. Don't split into two wires on pins 7 & 8 until after the ammeter.

Record the values with the start/stop switch open (stopped), then record again closed (run).

The manual says max running current should be 1.1 A. They don't say what it should be stopped (switch open) but I would expect it to be low, probably less than 0.1 A.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

It isn't super clear in the instructions, but I believe TMP normal status on pin 2 is a passive voltage used for reporting info and for driving an optional relay.

Note how for pin 1 , it says "close w.r.t. pins 5 and 6" whereas for pin 2, it says "closeD w.r.t. pins 5 and 6". "Closed" with a d on the end.
tmp-normal-status.jpg
tmp-normal-status-2.jpg
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

I added the the 10,000 uF capacitor. It is polarized, so negative goes on the negative terminal. It drank electrons for a few seconds to fill up, then I switched on the turbopump but it is still not working, the same as before.

I emailed Edwards yesterday, even though I should have done that days ago. I'm not sure if they will reply without a support contract. Of course I am not the original owner.

Edit: better image
intput-filter-ac-dc.jpg
Last edited by Arun Luthra on Thu Sep 19, 2019 10:32 pm, edited 1 time in total.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

It is a linear bench DC supply, max 30V and 5A. It is feeding a DC to DC booster that upconverts 30V from the DC supply to 80 V out of the booster.

I recall how to measure current now.

I don't have a second meter at the moment but I can tell you that the DC supply reports 0.2A draw and about 6.5W.

I set a current limit on the DC supply as high as 4.5A without success.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Chris Giles »

Hi Arun,

please connect your DMM as shown in Rex's diagram and report back what you measure. This is the Output of your DC-DC converter. If you only have one DMM, then you can measure the voltage and current in two separate tests. Leave pin 2 disconnected.

Also can you draw a schematic diagram that shows it exactly as you have it connected - i.e. like Rex's diagram but expanding the "80V PSU" box to show how you have connected the 2 power devices. Please show where the lines marked 0V and GND in the photo are connected. Pin 3 is the chassis ground which you must connect to the mains earth, i.e. the centre pin of your AC wall socket. Pin 5,6 must go to the -ve o/p of your DC-DC converter not the 30V PSU (although you could connect these together).

If you have connected a cap over the 80V output please ensure it is at least 80V rated (100V is a common rating). Anyway, for now just remove it. That is not going to be the cause of your current problem and it could cause you danger from a shock as it may hold charge for a while - 80V may be enough to give you a kick.

Best regards
Chris
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Artem Artemov »

I have such pump, but on 24 volts. Works without problems. Try another connection.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Artem Artemov »

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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Cristiano_Machado »

Artem, I also have this pump and I suggested to connect pin 2 to pin 5 and 6. I agree with you that this will correct the problem.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

Do you have a version of the instructions where it says to connect pin 2 to 5 and 6 on the EXDC80, 9 pin 80V unit?

The negative (-) on the booster is about 2V different from ground. Does this matter?

I did some load tests on the DC Booster output:

- With a total resistance of 75 ohm in wire wound resistors, it supplied the specified 80.0V, while 1.067A went through the resistors for a power of 86.4W. The DC supply was set to 30V output, had 3.08A and 92.3W. (Efficiency about 93.6%).

- With 50 ohm in wire wound resistors, the expected wattage was 128W through the resistors, however the DC booster was not able to provide 80V.
- When the DC supply was set to 19V, it went into current limit mode, using 94.6W at 5A. The booster limited itself to 65V and had 1.32A. (Current limited at 19V and higher on DC supply.)
- When the DC supply was set to 18V, it was not current limited, it used 84W and 4.68A. Of course the booster could not sustain 80V here either, it was at 61.8V and supplied 1.24V (76.6W).

The EXDC80 is supposed to take 70V-85V, and it says 93W on the label. That implies 1.16A and 69.0 ohm at 80V.

Somewhere in between 50 ohm and 75 ohm, the system is not able to provide 80V output... the EXDC80 does fall in that range, but closer to the 75 ohm end...
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