04-500 Old style X-ray source filament conversion

Posted on January 22, 2019 by Randy

The very early PHI 04-500 and 04-548 X-ray sources used a small filament that had couplers to make the connection between the X-ray source and the filament.

04-500 04-548 old style filament

In addition, the couplers were held in place with a notched ceramic that had a special pointed set screw which pressed into a copper wire that in turn made the connection to the electrical feedthrough on the source.

This connection scheme worked well enough as long as you set the filaments properly and did not ramp the current up too quickly. Even then, the filaments were prone to warping out of shape over time. Also the couplers could loosen up and then the filaments would short out.

PHI’s solution was to redesign the filament where the filaments were brazed into a ceramic base instead of using couplers. This resulted in a very stable filament base where the filaments can’t move at all and so they no longer warped out of position (unless you ran the filament current up too quickly).

Recently I updated an older 04-500 X-ray source from the old style to the new style filaments. You can see the before and after in the pictures below.

Old Style 04-500 X-ray source

Updated 04-500 X-ray source

This update will result in more stable X-ray source operation and extended filament lifetime.

The new style filaments cost more than the old style filaments by quite a bit. But factoring in the improved performance, longer lifetime and reduced downtime it may be worth the additional cost.

If you have an old style source please keep this filament conversion in mind the next time you need filaments or a complete source rebuild.

Contact RBD Instruments for more information.

Hydraulic quick coupling seal replacement

Posted on November 1, 2018 by Randy

The Hydraulic Quick Couplings (quick connect) used on PHI X-ray sources are Parker type SH2-62.

These couplers are used to connect the heat exchanger to the X-ray source in order to keep the anode from overheating. Over time the seals in the female coupler can fail from wear or simply drying out. When that happens you will get a steady drip of water from the coupler (not good as if water leaks into the source it will arc) .

This post will explain how to find and replace the seals in the female coupler. The male coupler is non serviceable (but also usually does not fail). Some pictures of the fitting and seals are at the bottom of this post.

There are two parts to the seal mechanism.

A Teflon seal retainer
A Nitrile O-ring seal

You can find these parts at any Parker distributor (Google Parker quick coupling) or by searching for the part numbers.

The Teflon seal retainer is PN MS28774-015

The Nitrile O-ring is PN 2-015 N1470-70

If you search for the part numbers you will find lots of places that carry these parts. They are very inexpensive. In fact, the next time you order parts from RBD for your PHI X-ray source just ask and we will throw some in with your order at no charge.

Once you have the parts, here is how you install them:

Use a dental pick and dig out the Teflon spacer and O-ring
Install the new O-ring. You can use the dental pick to guide it into the channel. Note that the O-ring needs to be towards the bottom of the coupler
Install the new Teflon spacer using the dental pick to guide it into the channel. Note that it needs to be installed towards the top of the coupler. Also, for the Teflon spacers that I purchased for this blog post, they have a slit in them which is probably supposed to make it easier to install. However, I think it would have been easier with a solid spacer like the old one I pulled out. It was a little bit tricky but by using a screw driver I was able to flatten the slit so that it finally snapped down into the channel. You should plan on losing one or two of the Teflon spacers as you refine you technique.

Finally, here is a link to a the Parker Hydraulic Quick connect catalog – 3800-B_Hydraulic.

male and female couplers

Coupler with leaky seals

old spacer and seal

Screwdriver and dental tool

Coupler with new seals

Hastings RV-16D Vacuum Gauge Repair

Posted on October 16, 2018 by Randy

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.

Failed Resistors on RV-16D

Failed Resistors on RV-16D schematic

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.

TC gauge before repair

TC gauge after repair

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.

49 ohm resistor

If you need technical assistance or parts for the AVC or replacement DV-6M tube please contact us here.

Bonus

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.