Checking For Light Leaks - Teledyne 200E Instruction Manual

Instrument Maintenance
• Turn off power to the instrument and vacuum pump. Remove the analyzer cover and
locate the reaction cell (Figure 9-6, Figure 11-7 and Figure 3-7).
• Unscrew the 1/8" sample and ozone air tubes from the reaction cell
• For orifices on the reaction cell (Figure 9-6): Unscrew the orifice holder with a 9/16"
wrench. This part holds all components of the critical flow assembly as shown in
Figure 9-7. Appendix B contains a list of spare part numbers.
• For orifices in the vacuum manifold: the assembly is similar to the one shown in
Figure 9-7, but without the orifice holder, part number 04090, and bottom O-ring
OR34 and with an NPT fitting in place of the FT 10 fitting. After taking off the
connecting tube, unscrew the NPT fitting.
• Take out the components of the assembly: a spring, a sintered filter, two O-rings
and the orifice. For the vacuum manifold only, you may need to use a scribe or
pressure from the vacuum port to get the parts out of the manifold.
• Discard the two O-rings and the sintered filter and clean the critical flow orifice in a
ultrasonic cleaner for about 30 minutes using methanol. Let the part dry.
• Re-assemble the parts as shown in Figure 9-7 and re-connect them to the reaction
cell manifold or the vacuum manifold.
• Reconnect all tubing, power up the analyzer and pump and - after a warm-up period
of 30 minutes, carry out a leak test as described in Section 11.5.1.

9.3.11. Checking for Light Leaks

When re-assembled or operated improperly, the M200E can develop small leaks around the
PMT, which let stray light from the analyzer surrounding into the PMT housing. To find such
light leaks, follow the below procedures. CAUTION: this procedure can only be carried out
with the analyzer running and its cover removed. This procedure should only be carried out
by qualified personnel.
• Scroll the TEST functions to PMT.
• Supply zero gas to the analyzer.
• With the instrument still running, carefully remove the analyzer cover. Take extra
care not to touch any of the inside wiring with the metal cover or your body. Do not
drop screws or tools into a running analyzer!
• Shine a powerful flashlight or portable incandescent light at the inlet and outlet
fitting and at all of the joints of the reaction cell as well as around the PMT housing.
The PMT value should not respond to the light, the PMT signal should remain steady
within its usually noise.
• If there is a PMT response to the external light, symmetrically tighten the reaction
cell mounting screws or replace the 1/4" vacuum tubing with new, black PTFE tubing
(this tubing will fade with time and become transparent). Often, light leaks are also
caused by O-rings being left out of the assembly.
• Carefully replace the analyzer cover.
• If tubing was changed, carry out a leak check (Section 11.5.2).
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Model 200E Instruction Manual
044100102 Rev A