I am helping a surgeon with his Ohmeda 7800 vent off this Exel 210 Anesthesia machine. Nice American technology from the late 1980s using the 8031 ROMless 8051 processor. Nice to see this - something serviceable but there are no technicians in Dallas or perhaps anywhere else who will touch it. He is faced with possibly having to purchase a new machine due to a voltage calibration error on the vent (Vent fail 6 as above). I want to test the vent away from the anesthesia machine and calibrate the voltages as per the service manual. 

I noted that the vent does not operate as soon as the DB25 cable is removed from the machine. This cable interfaces the oxygen sensor on the machine to allow the user consolidate FiO2 and O2 level warnings onto the 7800. However, the 7800 also receives some sort of signal from the Excel 210 which powers 'on' the vent through this DB25 connector.  This signal no doubt comes in the form of either a switch closure (or opening) or a voltage level on one or more pins as the vent 'turns on' when both its switch is 'on' and the anesthesia machine switch is 'on'.

What is the 'hack' to apply to the female DB25 end of the cable to allow the vent to operate off the machine. The O2 functions will, of course, not work without the sensor and associated circuitry but perhaps I can turn 'on' the vent while it's away from the machine if I can simulate the 'on' state of the machine thru the cable.

Perhaps there is not an easy hack to emulate connection to the machine but I would assume this vent can run independent of the machine with the proper inputs.

BTW, the vent won't go into calibrate mode off the machine apparently.

The very last page (9-20), page 286, shows the pinout of this connector that feeds 15 wires to the internal workings of the vent.

Cheers!

Most common failure for vent fail 6 message.

Who needs hard a copy of this manual. I have 1 binder. Best plea gets it.

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