The Hastings RV-16D thermocouple vacuum gauge is used in the Physical Electronics’ (PHI) Auto Valve Control (AVC) to read the vacuum in the load lock and also at the turbo pump. There are two DV-6M thermocouple sensor tubes connected to the back of the AVC and a relay selects which one is routed to the RV-16D vacuum gauge.
The 0 to 10mV output of the RV-16D (also called the “Hockey Puck” ) goes to a comparator circuit in the AVC and is ultimately displayed on a LED segment graph on the AVC remote. One bar on the AVC remote indicates up to air and 5 bars indicates less than 5 X 10-3 Torr.
When the Hockey Puck in the AVC fails, it is usually because one of the DV-6M thermocouple sensor tubes failed and in turn some of the resistors inside the RV-16D overheated. This blog post will show you how to repair the RV-16D by replacing those failed resistors with higher wattage ones that should be able to survive the next time one of the DV-6M gauges fail.
The layout and schematic below show the resistors that usually fail. R 3 is a 15K ohm 2 watt resistor and R 4 is a 100 ohm 1/2 watt resistor.
It is recommended that when you replace these resistors that you increase the wattage. For the repairs in the photos below, I used a 15K ohm 5 watt resistor and a 100 ohm 2 watt resistor. These resistors are readily available from Digikey, Newark and Mouser.
And since I already had the RV-16D torn apart I also replaced the capacitor C1 with a new one.
When working on the RV-16D be sure to completely unplug the power to the AVC. I recommend pulling the AVC completely out of the electronic rack or vacuum console. The RV-16D is located in the back left hand corner of the AVC. If your RV-16D has the metal cover on it you will need to remove it and either cut it around the wires or un-solder the wires an feed them through the case. Use your cell phone and take some pictures for reference before you un-solder any wires so that you can be sure to put them back in the exact same place. You do not need to replace the cover, the RV-16D will run cooler without it.
One final note. The schematic is not 100% correct as there is a 49 ohm resistor that is tied across the output on most of the RV-16D gauges that I have pulled apart. I think that this resistor replaces R5 and R6 as R6 is not needed since only the 10mV recorder output is used in the PHI AVC. If your RV-16D does not have the 49 ohm resistor, then I recommend that you add one. It will help to stabilize the output.
If you need technical assistance or parts for the AVC or replacement DV-6M tube please contact us here.
Since the AVC was out anyway, I replaced the pots from the RV-16D (R1 , 1 K ohm) and also the bar adjustment pot in the AVC ( R 103 / K6 25 K ohm) to the AVC front panel with 10 turn 2 watt precision potentiometers and also installed an isolated BNC connector to the RV-16D recorder output wires (Blue and black).
This modification makes it much easier to adjust the RV-16D recorder output when you install a new DV-6M tube and to adjust the AVC for 4 bars when the load lock is pump out. The 5th bar on the AVC remote is on a timer and will turn on after the 4th bar stays on for 2 minutes.
With this modification installed it is not necessary to remove the AVC cover to adjust the hockey puck output or the AVC 4th bar.