20-040 X-ray source power supply LOCAL REMOTE switch

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The 20-040 X-ray source power supply is used on some of the older PHI X-ray photoelectron spectroscopy (XPS) systems. There is a switch on the back of the 20-040 that needs to be set to the LOCAL position. When in the LOCAL position the high voltage is set by the user but the 32-095 or 32-096 X-ray source control turns the 20-040 high voltage on and off. Sometimes the LOCAL / REMOTE switch can become oxidized in which case the 20-040 high voltage may not turn on. This post explains how to remove the LOCAL / REMOTE switch and hard wire the board to the LOCAL position.

20-040 front panel
20-040 front panel

Make sure that the 20-040 main power switch is OFF and then unplug all cables from the back of the 20-040 and remove the 20-040 from the electronics console.

Remove the top cover (8 cross head screws).

Unscrew the nut on the LOCAL / REMOTE switch and also unscrew the two nuts on the 15 pin connector. Unplug the 3 pin connector on the top of the board, the larger bottom connector can stay attached.

On the back of the little board that the LOCAL / REMOTE switch is attached to you can see where the switch is soldered to the board. Un-solder and remove the switch. A solder sucker works well but you can also use some solder wick.

Solder some jumper wires between the pins as shown in the image below.

20-040 board with jumpers installed

Reattach the 3 pin connector and then insert the 15 pin connector back into the slot and use the two nuts to attach the board to the back chassis. I also added a plastic screw and nut to block the hole that remains after removing the switch. You can also just leave that hole open.

Plastic nut
Hole plugged

Replace the cover and tighten the 8 cover screws.

Make sure that the 20-040 main power switch is still OFF and then insert the 20-040 back into the electronics console and reattach all the cables to the back of the 20-040.

Below is a table that shows the pin outs on the control cable that goes between the 32-095/6 and the 20-040.

Removing the LOCAL / REMOTE switch eliminates the switch as a cause of lack of high voltage with the 20-040. If your 20-040 does not work and can’t be repaired, then RBD Instruments provides a drop in replacement, the 20-042.


32-095 and 32-096 X-ray source control faulty capacitor – urgent!

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Recently, I have seen the same problem on several 32-095 and 32-096 X-ray source controls which are used on older Physical Electronics PHI X-ray photo electron spectroscopy systems.

The issue is that C9, a 680 uF electrolytic capacitor blows out and the electrolytic material leaks out on the board.  Left unattended, the electrolytic etches and oxidizes the traces on the board.

If you have an older PHI XPS system that uses a 32-095 or 32-095 X-ray source control you should pull if out of the rack, remove the cover and inspect the board immediately.

If corrosion is present, then remove the board and remove C9.  Note the polarity of C9 as the + indicator on the board may be etched away.  Then, carefully clean the corrosion from the board as best as you can.   If in the shop I use some Alconox and let it sit on the board for a while, then rinse with DI water and let the board dry overnight.   In the field I have used isopropanol or methanol and cotton swabs.    Note that if the traces are corroded badly then they may come off the board as you clean it.  If so, you will need to use some fine copper wire to rebuild the traces.

Once the board is clean and dry, replace C9 with a new one.  I will dig into this issue some more and try to determine why this problem occurs so often and come up with a permanent solution.  In the meantime, I would recommend that the C9 capacitor be replaced every 5 years.

The pictures below show where C9 is located on the control board and what the corrosion looks like.

C9 removed
C9 location
C9 Neg towards connector

Low Cost Low Cost Molecular Sieve Trap

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Update 5-28-23 – We tried this on two different pump set ups and it seemed to work well at first. But on one of the set ups the fine mesh O-ring became clogged with small Zeolite pieces and plugged up the line. We removed the Zeolite from that set up, the other one is working fine so far. It could be a function of the mesh size, we will continue to monitor set up #2.

Molecular sieve traps use zeolite pellets to adsorb water vapor, oil vapor and other gas molecules. They are particularly useful in preventing the back-streaming of oil vapor from the rotary vane pump into the turbo pump and vacuum chamber.

Molecular sieve oil mist trap

Molecular sieve traps are placed between the rotary vane backing pump and the turbo pump. Most molecular sieve traps also have built in heaters that are used to regenerate the zeolite once it becomes saturated with contaminants.

If you have an oil filled rotary vane pump, a molecular sieve trap is a must.  However, molecular sieve traps can be relatively expensive running from $500.00 to $1,000.00 or more depending on the size.

This blog post shows a way to use existing flexible metal hose to make a molecular sieve trap for a lot less.

The general idea is to fill an existing flexible metal hose which is connected between the roughing pump and the turbo pump with zeolite pellets.

Step one is to remove the flexible metal hose.

Next, insert a mesh screen centering ring on the end of the flexible metal hose that is closest to the roughing pump. Connect the flexible metal hose to the roughing pump.

I used this one from LDS – https://www.ldsvacuumshopper.com/nwstceri.html

The next step is to fill the flexible metal hose with Zeolite pellets.  I used these Zeolite pellets (also from LDS) – https://www.ldsvacuumshopper.com/mositrb1zepe.html

Once the flexible metal hose is filled completely (leave a little bit of room at the top) connect the flexible metal hose back to the turbo pump roughing port using another mesh screen centering ring.

Finally, label the flexible metal hose to indicate that the flexible metal hose is filled with Zeolite pellets.  

That way when the flexible metal hose is removed at some point in the future who ever removes it will know that they need to remove the top of the flexible metal hose first and to empty the Zeolite pellets before removing the flexible metal hose from the roughing pump.   You can also hold the bottom centering ring as the flexible metal hose is removed from the roughing pump. (That is one advantage that a regular sieve tap has is that the Zeolite pellets are contained and will not spill out when the sieve trap is removed from the backing pump).

In the experiment where I tried this idea the turbo pump and backing pump worked normally, there was no noticeable increase in the pumping time.   At some point in the future when the Zeolite needs to be baked out heating tape could be used.  Or the Zeolite pellets could just be replaced with new ones. Note that the volume of Zeolite pellets in the flexible metal hose is much less than what a regular sieve trap has, so the amount of adsorption would be reduced proportionally.  Even so I think that this is worth considering, especially in situations where there is no existing molecular sieve trap installed.

Total cost for the two mesh screen centering rings and the Zeolite pellets was under $90.00 Finally, if you are not familiar with LDS you should check them out.  They have a wide selection of vacuum related hardware at good prices and fun categories like REALLY Cheap Stuff and Surplus items.  https://www.ldsvacuumshopper.com/drypumps1.html