Author Archives: Randy

Testing fan airflow on cooling fans on a PHI AES or XPS system

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The electronic racks in many of the older Physical Electronics / PHI surface analysis systems use fans to provide airflow to cool the electronic units and card rack boards. As part of the yearly preventive maintenance on these systems the fans should be inspected and replaced as needed.

A dead fan is easy to spot as the blades are not spinning at all. But for the fans that are spinning, how can you determine where the fan is providing good airflow?

There is an effect that we have all seen called the Wagon Wheel Effect.  The phrase comes from seeing wagon wheels that appear to be spinning backwards or even not spinning at all in old west movies and TV shows.  What it is really is just the frame rate of the movie or TV camera and how it syncs to the spinning wheel.  You can see this effect on the card rack fans due to the 50 or 60 Hz fluorescent or LED room lights and even in outdoor steady sunlight due to the few milliseconds that the human brain needs to detect motion.

What this means is that you can’t be 100% sure of how fast a fan is spinning just by looking at it.  An Anemometer is a way to measure the velocity of air and is a great way to get a relative answer as to how much airflow the fan is putting out. For this blog post I purchased a TOPTES TS-301 on Amazon for about $30.00

TopTes TS-301 Digital Anemometer, Wind Speed Meter with 2.26-inch Big Backlight LCD Screen, Air Flow Meter for Sailing Surfing Drone Flying RC Plane Golf Shooting HVAC

This air speed measuring device is equipped with easily rotatable fan blades and measures air velocity in 6 units: Feet per minute (ft/m), Feet per second (ft/s), Miles per hour (mph), Knots (knots), Kilometers per hour (km/h), Meters per second (m/s) Value of wind velocity x10. 

For this blog post we used km/hour to get a relative fan air speed measurement. In the picture below we get a measurement of 15.3 km/h on a working fan.

Then comparing that to a non-working fan (the blades are not moving at all) we get a measurement of 4.1 km/h just from the air that is flowing past the defective fan.

All the good fans read close to 15 km/h and so the anemometer is a good way to confirm not only that a fan is working but that the airspeed is comparable on all good working fans.

Another way to get a relative airspeed indication is to use a small piece of paper such as a post it note and see how much the paper bends when held over a fan.

In the picture below we and see that a good fan bends the post it note by a noticeable amount. 

The non-working fan does not move the post it note very much at all.

This method is not as quantifiable as using an anemometer, but it is still better than just feeling the air with your hand.  You could also use a small piece of string.

The anemometer displays air speed, but fans are rated in CFM (cubic feet per minute).  If you want to convert air speed to CFM you need to factor in the area of the fan blades.  This blog post explains how to do that –

Checking Cooling Fan Performance Easily with Cheap Handheld Anemometer

Finally, when testing the fans you should also inspect and clean the air filters, this blog post shows where those are located –https://www.rbdinstruments.com/blog/preventive-maintenance-rbd-techspot/

10-610 Monochromator X-ray Source Re-Tipping Service

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RBD Instruments is now providing a re-tipping service for the 10-610 monochromator X-ray source anode. Besides installing a new copper tip, a diamond disc is inserted into the center of the copper tip and then the anode is coated with a thin coating of aluminum.

The thermal conductivity of diamond is about 5 times better than copper. By using diamond to improve the heat dissipation of the anode, the aluminum coating lasts significantly longer than the original anode and ensures that the anode will not melt once the aluminum coating is eventually worn off.

diamond tipped x-ray source anode

If the original anode was operated for more than the recommended lifetime of 1,100 hours it was possible for the anode to melt a small hole in the center of the anode and leak water into the vacuum chamber. The image below shows a 10-610 anode that is worn out and very close to developing a leak.

Melted 10-610 X-ray source anode

Sometimes this would show up as a change in the chamber vacuum when the X-ray source was turned on. Other times it would result in a lot of water leaking into the vacuum chamber with catastrophic effects on internal parts such as the ion pumps and the MCD chevron plates. These results are in addition to all the water vapor created in the vacuum chamber. (RBD also provides various products for removing water vapor from vacuum systems.)

The 10-610 monochromator X-ray source re-tipping service will prevent the water leakage issue, no matter how many hours you have on the anode.

For more information contact us at https://www.rbdinstruments.com/phi/optics-parts.html

PHI XPS System Specimen Stage Motor fix

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The PHI 5400 and 5600 LS (large sample) XPS systems and some of the 5600 and 5700 systems use motors to control the specimen stage via the system control software.

Over a period of many years, the motors can slow down or suddenly stop moving.

This blog post will show you how to possibly solve the problem.

The motors used on the PHI automated specimen stages are TRW precision fractional-horsepower motors. These motors are no longer made but you can sometimes find them on eBay.

In the example below, this motor was working fine and suddenly stopped moving. Lubricating the motor shaft solved the issue.  If you have a PHI automated specimen stage where a motor is sluggish or stopped working, try lubricating it as shown below. If lubricating the motor does not solve the problem, then the motor might be bad and need to be replaced.

Procedure

Remove the defective motor from the specimen stage and set it on a flat surface with the white motor cover facing up.

stage motor

Remove the white plastic cap (2 screws).

Using 3 in 1 oil, put a few drops onto the end bearing and let it soak in for 15 minutes. When the oil is complexly drained into the bearing, apply a few more drops and let it soak in for 15 more minutes. IMPORTANT! Do not use WD40.  That may work short term but long term it will dry out the lubrication on the motor shaft and cause it to seize up.

Wipe off any excess oil and then replace the white plastic cap.

Connect the motor cable back up and test the motor using the software. Do not connect the motor to the specimen stage at this point.

 If the motor now works, you can reconnect the motor.  In the case of an LS system, you need to put the specimen stage into the bakeout position. Then manually set the repaired motor feedthrough to the bake out position and install the motor.

In the case of a 10-323 or 10-325 specimen stage, you need to set the stage to the correct position and set the motor to the correct position in the software before attaching the motor.

Read the blogs below for more information about your specific specimen stage.

LS intro and LS stage notes

71-205-7 / 10-325 Motor installation procedure