V4 Differential Valve Problem

V4 Differential Valve Problem

This post describes how to fix the problem of the V4 differential valve not opening on an AVC when the DIFFY PUMP ION GUN button on the AVC remote box is depressed.  Look at the photos at the bottom of the post for additional information.

The AVC (Auto Valve Control) has two DV6M thermocouple gauge tubes which are used to monitor the vacuum levels in the load lock and at the turbo pump. In the case of systems that have two turbo pumps, the second thermocouple gauge tube monitors the ion gun differential pumping turbo. The load lock TC gauge tube is located on under the load lock or in some cases as shown below, under the table top.

The AVC displays the vacuum level of the load lock thermocouple gauge at all times with the exception of when the DIFFY PUMP ION GUN button on the AVC remote box is depressed. In that case the AVC will momentarily monitor and display the turbo pump thermocouple gauge tube. If the vacuum level is sufficient then V4 will open. Monitoring the turbo pump vacuum is a built in safety feature of the AVC to prevent the chamber from being dumped in case the DIFFY PUMP ION GUN button on the AVC remote box is depressed while the turbo pump is off or not up to speed.

A not uncommon problem with the AVC unit is that the V4 valve will not open when the DIFFY PUMP ION GUN button on the AVC remote box is depressed.

The most common solution to this problem is that the turbo pump thermocouple gauge tube is not working properly or is not matched closely enough to the load lock gauge tube. Here is how you can test the ion gun gauge tube –

  1. Press the PUMP INTRO button on the AVC remote and pump out the load lock until you have 5 bars displayed on the AVC remote.
  2. On the back of the AVC (located on the back of the vacuum console), remove the TC1 gauge cable. TC1 monitors the load lock.
  3. Unplug the TC2 cable and move it into the J1 connector where you just unplugged TC1.
  4. Look at the AVC remote box. If the turbo pump thermocouple gauge is working properly you will see 4 bars displayed. After 2 minutes you should see 5 bars displayed.   If only 3 bars are displayed you can adjust the AVC so that V4 will open by following the steps in this older blog post – http://www.rbdinstruments.com/blog/auto-valve-control-adjustment-procedure/

If only 2 bars are displayed then the next step would be to try replacing the DV6M thermocouple gauge tube. There is only one TC controller (Hastings T6 called the hockey puck because of its shape) inside the AVC and a relay switches between the two thermocouple gauge tubes when the DIFFY PUMP ION GUN button on the AVC remote box is depressed. If the two thermocouple gauge tubes do not have similar offset and gain properties then the only solution is to replace the turbo pump DV6M thermocouple gauge tube or the intro thermocouple gauge tube in order to get them to match more closely. If the AVC reads 1 bars all the time then the hockey puck may be defective.

Usually though, the problem is that the thermocouple relay inside the AVC is not switching. Or the contacts on the relay may be dirty. In the case of the older Blue plastic relays it is common for the plastic switch throw to be cracked at the top in which case the relay may close but not all the way and so the turbo pump thermocouple gauge is not read at all.

If when you swapped TC1 and TC2 only one bar was displayed, then most likely the relay I broken or the contacts are dirty. Here is how to address that problem;

  1. The easiest way to get to the back of the AVC is to come in through the top. So, remove the wooden table tops and the aluminum ones that are towards the back of the vacuum console.
  2. Close all valves on the AVC and also turn off the turbo pump (s).
  3. Turn off the AVC control power.
  4. Remove cables from the back of the AVC, including the power cord.
  5. Unplug the air manifold cable and remove the gas manifold from the AVC (2 to 4 screws) The air-lines stay connected to the manifold and the compressed air that is connected the back of the vacuum chamber stays on..
  6. Remove the AVC control and unplug the 40 pin remote box ribbon cable.
  7. Place the AVC control on a work bench or table and remove the cover.
  8. Inspect the TC relay K3 (on older AVCs there are only 2 relays and the thermocouple gauge relay is the left one). If you have a newer AVC with 3 relays, the TC relay is the far left one. The far right one is the up to air relay. If it is the old blue relay you can remove the two mounting screws on the back of the AVC to make the relay more accessible.
  9. If the TC relay is the old Blue plastic type then most likely the relay contact pull piece is broken at the top. If you remove the cover you can inspect the top part of the pull piece and if it is cracked then the relay needs to be replaced. (You can also just move a new pull piece over from a new relay rather than unsolder the relay).
  10. If the TC relay is the newer style then most likely the contacts are oxidized and you will need to clean the contact with some fine sand paper or emery cloth followed by paper soaked in isopropanol to remove the residual small particles. (Or you can replace the relay with a new one).
  11. To clean the contacts, unplug the relay from the socket and remove it from the AVC.
  12. Remove the plastic cover from the relay (it snaps on so use small screwdriver to un snap it) then clean the contacts.
  13. You can measure the resistance on the contacts with an ohm meter and manually move the relay throw to switch between the two sets of contacts.
  14. Reinstall the relay.
  15. Reinstall the AVC control and reconnect the gas manifold and all the cables.

That should do it!   If not then please contact RBD Instruments Inc. for more assistance. We can repair your AVC controller and also provide DV6M thermocouple gauge tubes.

RBD Instruments Inc. www.rbdinstruments.com 541 330 0723

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Endoscopic ion pump inspection

An easy way to determine whether or not an ion pump needs to be rebuilt is to perform an endoscopic ion pump inspection. The hard way is to drop the ion pumps.

In the last few years the prices have really come down on USB and android/iPhone endoscopes. If you do a search on EBay for USB endoscope you will see a lot of choices for under $20.00. The one used in this blog post is 7mm in diameter, which is small enough to fit into a 1.33” CF flange hole.

endoscope

endoscope

endoscope_for_phone

endoscope_for_phone

 

 

 

 

 

 

For this example we inspected a PHI 660 scanning auger system equipped with a 220 l/s ion pump. This system has been in use for about 10 years primarily for depth profiling using Argon gas.

Since there is a shield below the TSP filaments the only way into the ion pumps was thru the un-used 1.33 CF flange that is opposite the ion pump high voltage connector.

This video link shows what it looks like as you move the endoscope around inside the ion pump – https://www.youtube.com/watch?v=5DQVW3DCG9A&feature=youtu.be  Note that the video has a blue tint to if from the built in LED camera lighting.

The color corrected pictures below show that the ion pump elements are pitted, the insulating ceramics are coated and there are some flakes in the bottom of the pump well.   The conclusion was that the pump elements have another year or so left on them and so we will plan on replacing them in 12 to 18 months.

ion_pump_cf_flange

ion_pump_cf_flange

endoscope_inserted

endoscope_inserted

High_voltage_feedthru

High_voltage_feedthru

flakes_in_pump_well

flakes_in_pump_well

Pits_on_titanium_plate

Pits_on_titanium_plate

coating_on_ceramic

coating_on_ceramic

 

 

20-327 Beam Voltage Adjustment

This post is about how to adjust the 20- 327 2kV beam voltage for the elastic peak.

Click on the link below to go to the .PDF

20-327 beam voltage adjustment

The 20-327 electron gun control is used on the Physical Electronics 610 series scanning auger electron systems.  The 20-327 is also a replacement for the obsolete 18-080 and 18-085 electron gun controls.

20-327 front panel

20-327 front panel

Once you have adjusted your elastic peak for best shape with max counts you will need to adjust your 20-327 R47 for proper alignment of the beam voltage calibration. Please read all of procedure before proceeding.

1)    Place a piece of clean copper in your system, Run an alignment and adjust your Z axis until you get good counts with good shape. Not one or the other but both.

2)    NOTE: DO NOT MOVE STAGE FROM THIS POINT ON.

3)    You will not care about the position of the peak we will adjust this in the 20-327.

4)    Acquire a survey and adjust the AES scale factor located in hardware properties until your copper peak is at 920 differentiated. Remember in the scale factor adjustment higher value lowers the peak and lower values raise the peak

5)    Next run an alignment and see where your elastic peak is located. If peak is not at 2K move on to steps 6,7and 8.

6)     Turn the gun off in the software. Turn off the 20-327 drop down the front panel of the 20-327 and extend the bottom board (if you do not have an extender it will take you longer but can be adjusted.

7)    Adjust R47 located toward the back of the board located in diagram 1

8)    Adjust half a turn; replace the board and power up the 20-327 and Augermap software.   Run an alignment determine the direction the pot moves the peak. Adjust accordingly until your alignment is right on 2KV and then run a survey and make sure your Cu1 peak is 920 diff. If peak is not perfect run procedure (step 3 to 8 until elastic peak and Cu1 are in proper positional alignment).