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

RBD Software Windows Operating System Compatibility (February 2024)

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Microsoft Windows General Support

All of RBD’s software products (AugerScan/AugerMap for PHI Upgrades, Actuel for the 9103 USB Picoammeter, and CMapp for the microCMA Compact Auger Analyzer) are compatible with the latest version of Microsoft Windows (as of this post, Windows 11).

In general, RBD warranty supports all versions of Windows supported by Microsoft, which are currently Windows 10 and 11. We cannot guarantee support for previous versions, however all our software products are functionally compatible with Windows 7 through 11 with a few exceptions, and we can usually support Windows 7-8.

RBD maintains archives for versions of software compatible with even older operating systems.

Please keep in mind that for any legacy version of RBD software, any newer features and subsequent bug fixes will be missing.

Lifecycle FAQ – Windows | Microsoft Learn


Details for RBD’s Software Applications

PHI / Perkin Elmer System Upgrades (AugerScan and AugerMap)

Minimum Windows Version Recommended: Windows 7

RBD maintains versions of AugerScan and AugerMap that are compatible with Windows XP. We can provide versions that may be compatible with Windows 95 and 98, however driver support may not be possible, depending what interface cards are used in the upgrade.

For RBD 147 Interface Cards in the PCI format, drivers are available for Windows XP, and Windows 7-11 32 and 64 bits.

For RBD 147 Interface Cards in the PCI format, drivers are available for Windows 7-11, 32 and 64 bits.

9103 USB Picoammeter

Minimum Windows Version Recommended: Windows 10

RBD maintains versions of the Actuel application for the 9103 that are compatible with Windows XP. There are no versions available for earlier operating systems.

(The 9103 USB Picoammeter itself is compatible with any operating system supported by the FTDI USB drivers if you chose to code/script your own custom application)

microCMA Compact Auger Analyzer

Minimum Windows Version Recommended: Windows 10

CMapp for the microCMA Compact Auger Analyzer is currently only compatible with Windows 10. While older versions may run on Windows 7 – 8, it is highly recommended that these are not used, as subsequent versions provide much better safety mechanisms for hardware control.


As always, contact RBD here for any questions you may have or versions of software you do not see available on the website.

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