Leakchecking Procedure

Leak Checking

Leakchecking techniques

• RGA should not have com cable plugged in without power cable plugged in. Don't just unplug power cable.

• Always turn the electron multiplier on!

• Work top-to-bottom (helium rises, so start on the top of the machine first to avoid false positives)

• Bagging flanges can be helpful.

  • Small leaks can take time to appear, but blowing helium all over the lab can lead to false positives (e.g. helium diffuses through the lab to the flange that is actually leaking)

• Sometimes bisection method is easier than brute-force for pesky leaks, e.g. bag top half of machine; if on top half, then bag source flange; if not on source flange, bag CAR; continue as-needed.

• Viton seals, outlet of scrolls, etc. can all look like leaks.

Residual Gases

• Tabulated from Homan's spreadsheet

  • More here: Molecular Weight Search

  • Or here: http://sdbs.riodb.aist.go.jp/sdbs/cgi-bin/cre_index.cgi

• Example of how to interpret spectra: Kurt J. Lesker Company

• Cracking patterns often available in the built-in SRS RGA software

• Isotope proportions for all the elements are at

-SRB: I tried nesting tables to make it more intuitive to edit, but there were issues...

Repairing RGA ECU

Last updated by SDM - June 2016

When to fix RGA ECU?

1. Partial pressure readings during an analog scan do not make sense, e.g. values are too high or the ratio for certain peaks do not make sense

2. RGA is reading negative values and wildly varying values during leak checking

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Broken analog scan

Open

Broken leak check

The fix

Sending the RGA to SRS costs ~$650 to replace a resistor and a transistor, which cost ~$1 alone and require ~15 minutes of soldering.

• Parts that you need to complete this repair can be purchased from Mouser, Allied Electronics, Digitkey, etc, but I'll give the Mouser links below

  • 1x 100 ohm carbon film, 1/4 Watt, 5% tolerance length ~ 6 mm (http://www.mouser.com/Search/ProductDetail.aspx?R=CF1%2f4C101Jvirtualkey66000000virtualkey660-CF1%2f4C101J)

  • 1x npn transistor, part # D44VH10G (part number is independent of saler), TO-220 (TAB) package type, with a through hole (http://www.mouser.com/Search/ProductDetail.aspx?R=D44VH10Gvirtualkey58410000virtualkey863-D44VH10G )

    • The RGA manual says it's just D44VH10, but that part contains lead and is no longer fabricated, but D44VH10G is the lead-free version

• Remove the outer cover of the ECU box (top and bottom) and disconnect the power cable between the two halves

• Remove the big threads (long rods) that normally screw into RGA flange when attached to the machine

  • Remove c-clips, washer, and rod on both sides (top and bottom)

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Removing C-clamp and long rod

• Remove the back plate

  • Fan screws

  • RS232 screws

  • Power pin screws

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Removing back plate

• Remove the bottom side PCB (i.e. not the resistor board -- i.e. the board with the femail RS232 and the red and green LEDs). You'll need to remove two screws from the side of the box before you can pull up this board.