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model 2XX series repair program PDF Print

The model 256B and model 257E were introduced in the late 70’. At this time they were the most advanced analog automotive gas analyzers available:

model 257E

The ability of the 256B and 257E to analyze multiple gasses is obtained by a single IR beam and a rotating filter wheel. The IR beam is chopped into four separate wavelength components which pass sequentially through the same region in the sample cell. Three of these components are used to measure the CO, HC and CO2 gases. The fourth is a reference wavelength used to measure optical transmission through the sample cell. The 256B and 257E use a temperature-controlled filter wheel, and a thermoelectrically-cooled and temperature-stabilized infrared detector, resulting in very low output noise and span stable operation. The sample cell’s dual inlets and central outlet for the sample gas, combined with recessed windows, ensure that HC hangup is almost eliminated. The infrared source is a highly reliable industrial grade component with power derated to only 50% of its specified maximum, yielding > 250.000 hours MTBF.

We offer two different types of services for your model 256B and 257E gas analyzers. The first one is a basic repair and the second one is a complete refurbishment.


Basic repair:

A basic repair takes care of the actual defect of the bench. After repairing the bench it goes through a complete calibration and adjustment procedure. All relevant datas will be kept on a service protocol.


Many OEM customers now have the opportunity to significantly extend their investment in gas analyzers through the exclusive Refurbishing Program. Using disciplined service policies, coupled with product knowledge and advanced equipment that only a experienced service shop can possess, Andros‘ trained refurbishing specialists return used model 200er series analyzers to original or better performance. The refurbishing procedure includes:

  • complete disassembly under controlled conditions and cleaning of all parts
  • exchange of chopper motor, sample cell, mica window and detector
  • exchange of the filter wheel with a improved 5 position filter wheel
  • repair of defective PCB‘s as required
  • reassembly, calibration and adjustment according to the latest procedures
  • all relevant datas are kept on a service protocol

Through this procedure, refurbished units benefit from component or process improvements that may have occurred since their original manufacture. As a result, a refurbished unit can perform even better than when it was new! Plus, goes the extra mile in customer service, tailoring its refurbishing programs specifically to customer needs based on model, application characteristics, turnaround requirements and other relevant factors.