Teledyne T101, Operation Manual, Page: 238 / 375

Troubleshooting & Service Teledyne ML - T101 Operation Manual
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9.5.15. HIGH VOLTAGE POWER SUPPLY
The HVPS is located in the interior of the sensor module and is plugged into the PMT
tube (Figure 10-13). It requires 2 voltage inputs. The first is +15 which powers the
supply. The second is the programming voltage which is generated on the Preamp
Board. This power supply is unlike a traditional PMT HVPS. It is like having 10
independent power supplies, one to each pin of the PMT. The test procedure below
allows you to test each supply.
Adjustment of the HVPS is covered in the factory calibration procedure in Section 9.6.4.
9.5.16. PNEUMATIC SENSOR ASSEMBLY
The pressure/flow sensor circuit board, located behind the sensor assembly, can be
checked with a voltmeter using the following procedure, which assumes that the wiring
is intact and that the motherboard and the power supplies are operating properly.
Measure the voltage across TP1 and TP2, it should be 10.0
±
0.25 V. If not, the board is
faulty. Measure the voltage across capacitor C2; it should be 5.0 ± 0.25 V. If not, the
board may be faulty.
9.5.16.1. Sample Pressure
Measure the voltage across test points TP1 and TP4. With the sample pump
disconnected or turned off, this voltage should be 4500
±
250 mV. With the pump
running, it should be about 0.2 V less as the sample pressure drops by about 1 in-Hg-A
from ambient pressure. If this voltage is significantly different, the pressure transducer
S2 or the board may be faulty. A leak in the sample system to vacuum may also cause
this voltage to be between about 0.6 and 4.5. Make sure that the front panel reading of
the sample pressure is at about 1 in-Hg-A less than ambient pressure.
9.5.17. IZS OPTION
The zero/span valves and IZS options need to be enabled in the software (contact the
factory on how to do this). See Figure 3-2 and 5-3 for a flow diagram with zero/span
valve or IZS option.
• Check for the physical presence of the valves or the IZS option.
• Check that a working perm-tube is installed in the IZS oven assembly.
• Check front panel for correct software configuration. When the
instrument is in SAMPLE mode, the front panel display should show CALS
and CALZ buttons in the second line of the display. The presence of the
buttons indicates that the option has been enabled in software. In
addition, the IZS option is enabled if the TEST functions show a
parameter named IZS TEMP.
The semi-permeable PTFE membrane of the permeation tube is affected by humidity. If
the instrument is installed in an air-conditioned shelter, the air is usually dry enough to
produce good results. If the instrument is installed in an environment with variable or
high humidity, variations in the permeation tube output will be significant. In this case, a
dryer for the supply air is recommended (dew point should be-20° C or less).