DGC III Filament Select Relay

The DGC III ion gauge controller (also called the DIG 3) used on many of the older PHI surface analysis systems can operate 2 ion gauges (only one at a time). There is a relay inside the DGC III that puts the filament current output to the ion gauge connectors on the back of the DGC III. Normally there is only one ion gauge on the vacuum chamber and it is plugged into the Ion Gauge 1 connector (normally closed) on the back of the DGC III. The relay is shown in the photo below.

DGC III filament select relay

If your DGC III does not read correctly, you can first check the +/-12V and +5V power supplies. Here is a link to some information on how to do that – DGC III power supplies test. If any of the power supplies are low and have a high AC component, then usually that issue is caused by a leaky capacitor on the power supply board. ** CAUTION! Make sure that someone who is trained on working safely with voltages up to 500V performs the voltage measurements. There are potentially lethal voltages inside the DGC III.**

If the power supplies check out OK then it is possible that the filament select relay is dirty. To test that, make sure that the DGC III is OFF and then move the black filament cable on the back of the DGC III from filament 1 to filament 2. You do not need to move the COL BNC cable as those are both tied together.

Turn the DGC III back on and press the 2 button. That will select ion gauge 2. Press the I/T 3 button to measure the vacuum and see if the DGC III works normally. If it does, then the filament select relay is dirty. You can just keep the ion gauge connected to ion gauge 2, or, you can clean the relay and connect the ion gauge back to ion gauge 1.

To clean the relay, make sure that the power is OFF to the DGC III and if not already down, pull the unit out of the rack and remove the cover.

Pull the relay out and remove the 4 screws on the bottom of the relay.

The contacts that are touching are the normally closed ion gauge 1 contacts. Use a small strip of some very fine emery cloth or sandpaper to gently clean the contacts on both sides. Then, use a small strip of paper with some isopropyl alcohol on it to remove the leftover grit. Replace the cover on the relay and reinstall the relay.

Ion gauge 1 should work properly now but if not you can order a new relay from companies like Grainger or Mouser. Just make sure that the pins match schematic that is on the side of the relay. Google 105 3PDT 10A relay and you will find it.

If your DGC III does not work and you need some help or a loaner, please contact RBD Instruments for assistance.

Operation of the DGC III Digital Ion Gauge Control

One of the more common questions that we get concerning the DGC III digital ion gauge control (also known as the DIG III) is how to enter the set point values. We created this video to demonstrate the basic operation of the DIG III including the set points.  For advanced operations, please refer to the DGC III ion gauge manual.

The PHI DIGIII Digital ion gauge controller provides an indication of the vacuum in the chamber, as well as 4 set points which are used to interlock certain system functions. A common problem with the DIG III is that the set points reset to zero after the DIG III is turned off or loses power. In most cases, that problem is the result of a worn out DIGIII battery and is something that the user can easily replace themselves – just be aware that the battery is soldered onto the set point board inside the DIG III.

The RBD Instruments part number for the DIG III Set point battery is BA3.6RE.

DGC III Set point values

These are the typical values used on most PHI surface analysis systems

After about 8 to 10 years, the set point operation can become intermittent due to oxidation of the contacts on K901 through K904 on the set point board.

Possible symptoms include:

  • The electronic card rack power drops out intermittently.
  • The X-ray source will not operate even though set point 3 indicates that it is on.

To repair this problem, simply remove the covers from the set point relays K901-K904 on the set point board and clean the contacts with some fine sandpaper or emery cloth.

Set point relays

Set point relays

DIGIII Setpoint Bypass Jumper

For other more serious DIG III problems, RBD Instruments can repair or exchange your defective control. For more information visit our website or call us at 541-550-5016