Author Archives: Randy

16-050 Heat Exchanger Flow Switch replacement procedure.

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The original flow switch for the 16-050 heat exchanger used 220 VAC for the input power.

About 10 years ago that flow switch was discontinued and was replaced with a similar model that used 120 VAC for the input power.  A 220 VAC to 120 VAC step down transformer was also needed.

Very recently, the 120 VAC input power flow switch was discontinued, and it has been replaced by another version that uses 24 VDC as the input power.  To provide 24V DC to the replacement flow switch a small 220VAC to 24 V DC power supply is needed.

This blog post will provide step by step instructions on how to install the new 24V DC flow switch and power supply into a 16-050 heat exchanger.

Step one is to drain the water from the heat exchanger.  The easiest way to do that is to remove the IN and OUT couplers from the X-ray source and then connect those to the IN and OUT lines. Mark the IN and OUT water lines to make sure that you do not get them mixed up.  Hold them over a clean container (such as a plastic waste basket) and then turn on the 32-095 or 32-096 X-ray source control. 

The 16-050 will turn on and water will come out of the source IN line.  After about 9 seconds the 32-095/96 will shut down the 16-050 heat exchanger due to insufficient flow.  Turn the 32-095/96 OFF for a few seconds, then back ON.  Repeat several times (it might take 10 to 15 times) until water stops coming out of the source IN line and the pump starts to make noise.  This will drain most of the water out of the 16-050.  You want to use a clean container for the water so that you can reuse the water.  Or you can replace the water after the flow switch has been replaced with distilled water from a grocery store.  Lab DI water does not always work.

After the water has been drained, turn the 16-050 heat exchanger front panel power switch to OFF.

Next, trace the power cord that is on the back of the 16-050 into the electronics console and unplug the power cord.  Make a note of where that power cord plugs into so that you can plug it into the same receptacle later.

Turn the 16-050 front panel power switch to ON just to make sure that the 16-050 power cord is unplugged.  Verify that the 16-050 motor does not turn on and then turn the 16-050 heat exchanger front panel power switch back to OFF. Do not work on the 16-050 if it is still plugged in!

Remove the top cover on the 16-050.

Remove the small cover that is located just behind the 16-050 power switch.  There are 4 nuts that need to be removed then the cover comes off.

Remove the wires that go to the flow switch.  Those will be TB1 sections 1, 2, 5 and 7.

Remove the old flow switch.  Use your phone to take pictures of where the IN and OUT lines connect on the flow switch.

Install the new flow switch making sure that it is connected EXACTLY the way that the old flow switch was.

Route the new flow switch wires up to where the old flow switch wires were.

The wires need to be connected as follows:

RAVCV04-24 power supply:

Blue to TB1 7

Brown to TB1 5

Red to Flow Switch Brown

Black to Flow Switch White

Flow Switch:

White to RACV04-24 Black (use twist nut)

Brown to RACV04-24 Red (use twist nut)

Red to TB1 2

Black to TB1 1

Green – Not used.

This drawing shows the connections –

Verify that the wires are all tight and then replace the little cover using the 4 nuts.

Reconnect the couplers and water lines to the X-ray source.  Make sure that you have the IN and Out going to the correct ports on the X-ray source.

Pour most of the water back into the reservoir or use 2-3 gallons of distilled water from a grocery store.

Plug the 16-050 power cord back in and then turn on the 16-050 front panel power switch.

Turn on the 32-095/96 and the 16-050 motor should turn on.  It will turn off after 9 seconds.  Turn the 32-095/06 off and then back on to reset the pump.  Do this a few times until the air bubbles work themselves out and the 16-050 pump motor stays on. 

You will need to top off the water reservoir once the water fills up the lines.  Do not overfill!

If the 16-050 will not stay on even when the water is full (close to the upper line on the water level indicator on the back of the 16-050) then the flow switch may need to be adjusted.

The flow switch adjustment potentiometer is on the back of the flow switch under a label. It is a small, slotted screw.

Try turning the flow switch a few turns CW and then turn on the 32-095/96.  If that does not work, try a few turns CCW plus a few more turns.  Once you get it to where the 16-050 pump stays ON then you can slowly turn the potentiometer the opposite direction until the red interlock light on the 32-095/96 turns ON, then adjust the potentiometer 1.5 turns the other direction until the red interlock light just turns off. The idea is that you want to set the potentiometer so that the 16-050 pump is ON when you have water flow, but you want to be somewhat close to the edge so that the 16-050 pump will shut off when the flow drops. 

Typical flow rates are 1.1 GPM for XPS systems with a 10-610 mono-chromator source and up to 1.8 GM for systems that have only a single 04-548 dual anode X-ray source.

The RBD Instruments Part number for the kit that includes the 24V flow switch and the power supply is FLOW-SWITCH-24-Kit.

For more information please contact RBD Instruments here – https://rbdinstruments.com/contact.html

DGCIII Power Switch Fix

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The power switch on the DGCIII Digital Ion Guage controller (sometimes referred to as the DIG III) which is used on many older Physical Electronics systems has a rocker switch that provides the mains AC voltage to the controller.

DGCIII power switch

This switch can get oxidation buildup over the period of many years and the result is that the DGCIII will not turn on.

That switch is no longer available, but this blog post will show you how to repair the switch and how to install a new switch if the existing switch can’t be repaired.

The power switch for the DGCIII comprises 2 sections that select the gain for the UHV, Bayard Alpert and extended ranges, and the higher current power switch section.

The power switch section is on the back end of the gang switch as shown in the picture below.

ON OFF rocker switch

Step one is to remove the two screws that attach the power switch to the gang shaft.  To do that, first unplug the power cord from the back of the DGCIII and remove the cover.

Remove the 4 boards that are inside the DGCIII. You do not need to remove the power supply board that is on the side of the DGCIII.

Use a small slotted screwdriver and remove the two screws.

Removing rocker switch section

Pull the power switch off the shaft.

Next, use a small screwdriver and lift the 3 tabs that hold the switch together.

Pull up on the 3 tabs

Separate the back from the power switch mechanism.

Remove back of rocker switch

Squirt some contact cleaner into the sides of the power switch and then use a needle nose pliers to rotate the flipper back and forth several times.  Add some more contact cleaner and repeat. Remove any excess contact cleaner with a wipe and Q-Tips.

Contact cleaner
Put contact cleaner in here
rotate contacts a few times

Use a meter and measure the resistance on the wires as shown in the picture below. When the flipper is to one side the contacts on the points shown below should have about 1 ohm of resistance, and they should be open going the other way.

Switch locations

If the switch checks out with an ohmmeter, then reverse the disassembly steps to reinstall the power switch section.

Replace the boards in DGCIII and replace the cover.

The DGCIII should turn on now when the power switch is turned ON.

If not, you can install a double pole single throw (DPST) panel switch in place of the rocker switch. You will need to drill a hole in the front panel of the DGCIII for the switch, and then move the wires over from the rocker switch section to the double pole single throw switch as shown in the above image.

Due to space limitations inside the DGCIII the DPST switch will need to be mounted sideways.  In this case the new DPST switch will turn the DGCIII on and off, and the original power switch will still control the ion gauge selection which is typically UHV. Make sure that the DPST front panel switch can handle 5 amps @120 VAC or more. A typical DPST switch is shown below.

DPST panel switch

If you need your DGCIII to be repaired, please contact RBD Instruments here – https://support.rbdinstruments.com/portal/en/signin

Model 99 ABS Current Preamplifier no signal problem

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The Model 99 Current Preamplifier is used on the older PHI (Physical Electronics) 660 scanning Auger electron spectrometers.

99 ABS preamp

There is a fairly common problem with this design of preamplifier where the input JFET can get damaged from sample arcing which results in a total loss of ABS (absorbed current) image.

The most common solution to this issue is to replace QN2 which is a 2N5546 dual JFET. These parts are obsolete but readily available on Ebay. You can also find equivalent replacement JFETs such as the EXR461.

To replace QN2, first remove the cover from the 99 ABS preamp.

The picture below shows the location of QN2.

Use a tweezers to pull up each leg of QN2 as you heat it with a soldering iron and then use a solder sucker or copper braid to remove all the solder from the holes on the circuit board.

Note the location of the tab that is on the circuit board and then bend the leads on the replacement 2N5546 so that the leads line up with the holes in the board. Press the 2N5546 down so that the pins are firmly in the holes, then remove the 2N5546 and cut the ends of the leads so that they are shorter. You only want about 1/8″ of the leads going into to the holes as otherwise the leads might short to the chassis.

Insert the 2N5546 into the holes and solder the lead wires to the board.

Replacing QN2 will likely restore the ABS image.

The schematic below shows that QN2 is the first thing that sees the input signal and so it makes sense that QN2 would likely be damaged from an arc. Also, JFETs are susceptible to arc damage more than a lower impedance device such as an op amp.

For help with repairs or maintenance on your PHI 660 (or other older PHI surface analysis systems) please contact RBD Instruments here – https://rbdinstruments.com/contact.html