Question and Answer - Cryogenic Freezers and Controllers

Q: I am informed that Japan operates on a 100V supply with their West Coast on 60Hz and their East Coast on 50Hz.  I tried to adjust the LN2 temperature for both cryogenic freezer probes A & B and in both cases it displayed (LN2 aborted). Next I went into the maintenance menu and discovered that LN2 was –273.1C. I rebooted the controller and found the same LN2 temperature.  Please explain how this reading occurred and how to correct the problem?

A: As per our reference material, it indicates that Japanese standard is 100-110VAC, 50-60Hz. The power supply used for Japan on the unit in question and in US for domestic applications is the same. It is made to function with US domestic standard nominal of 120VAC 60Hz. The tolerance on US domestic power is +/- 10% and on the low side it would be ~108VAC. The frequency would not be an issue because the power supply uses an unregulated step down transformer further negation of frequency issue, taking power supply to consideration, the controller rectifies it to DC internally and output is AC. From their outlets, if they are really getting only 100VAC then the output from the power supply to the control would be -20VAC. This would be trivial to properly operate the controller, so this should not cause the issue that is mentioned here.  If low voltage had been the issue, the controller would just shut off to a certain threshold voltage, which should be around the 20-21VAC point from the power supply to the control.

To correct this issue, you can replace the existing power supply with the new power supply which is currently use on the MDD units. It will provide the required output voltage with any input voltage from 100 to 250VAC and 50-60Hz since it built-in detector and switching device and is designed to accommodate +/-10%.  The MDD power supply should operate with an input as low as 90VAC or as high as 275VAC. It has been subjected to these extremes by TUV to be eligible for use in the MDD units. If you decide to install this power supply to sort out this issue, then P/N’s required to make the swap are as follows:

11795030 POWER SUPPLY 30VDC 1.2A 1 EA.

11859030 BRACKET POWER SUPPLY JEROME CE 1 EA.

11859021 BRACKET ADAPTOR FOR JEROME PS 1 EA.

2912191 PHPNHMS 4 EA.