We present here the possible causes and solutions for some of the common problems that may occur when operating a CM200FEG TEM. The information provided are collected and compiled from standard sources, such as Philips, as well as the expertise of experienced users of this lab. If you come to a problem, please check the list in the frame to the left. Click appropriate button and the descriptions and solutions will pop up in this frame. However, one may experience problems that are not listed here. Should you have solved such problems successfully, we would appreciate your sharing with us the solutions.

Program Hang-up.
Due to a variety of circumstances, the control program may experience a hang-up. If this occurs, proceed as follows:
1. Press STANBY (may not do anything), then RESTART (recessed button on top left of panel). Wait for the full microscope start up. When prompted (at least 20 minutes for vacuum startup), restart the FEG: warm start ok if less than 2 hrs since hitting RESTART).
2. If startup fails during internal checking of 5 program blocks, try again. If startup fails again, then download the CM Operating system as follows: Open program "CMDownload" on PC. Choose file cm125.exe. After program blocks fail, EM prompts "waiting for PC connection". At this time, initiate download with CMDownload program. After completion, sometimes EM restarts automatically, other times you must hit RESTART button. Maybe you even have to hit RESTART another time. Keep trying until successful or you suspect a hardware failure. 3. Prior to use, you must reset various parameters from default values (kV to 200, serial port to enabled, film number). 4. Check the overall instrument alignment. If the instrument performs as expected (unlikely), continue with normal operation. If the alignment appears to be lost, restore using 2 PC programs: FEG Registers (for gun alignments) and CM Monitor (for column alignments). Use recent files for restoration (this behooves you to also store these alignments at periodic intervals).

No High Tension. If everything else is normal, check the 24 V power supply inside the Power Supply cabinet. In order to test this, open the left-hand door with the key provided and check the two LEDs on the two lower rows of the power supplies. THese should be lit. If one of them is not lit, loosen then four screws approx. 2 cm and pull the unit out. Leave it disconnected in this position for 30 seconds. After this period, push the unit back into the rack, return to the operating panel and re-active the H.T. button.

No Emission. This could be due to one of the following:
1. If H.T. conditioning is selected on the first PARAMETERS page, it is not possible to heat up the filament.
2. After an extremely strong H.T. flashover, the 24 V filament current power supply in the power suplly cabinet may have switched off. If this is the case, continue as described in No High Tension, or if the control program is hang-up, proceed with first as described in Program Hang-up.
3. Filament has broken down. Change filament.

Spot Size Limited. When there is no specimen holder in the microscope, the spot size will be set to 5 and a spot size indication of XXX will appear on the microcontroller screen. As soon as a holder is introduced into the goniometer airlock, the spot size can be controlled again.

No Lens Currents (I). If there are no lens currents measurable when DISPLAY CURRENTS is selected on the PARAMETERS page, the column lifting circuit which automatically switches off the lens currents and HT may be active. Unauthorised attempts to operate the column lifting mechanism can activate the microswitch which controls the safety circuitry. This point should be checked if the lens currents connot be obtained when starting to use the microscope. Otherwise, check first water flow and if necessary reset it to the corrent value.

No Lens Currents (II). This occurred on October 24, 1996. All lens currents shut off and the cooling water floating sensors dropped off. Action: Remount the sensors and set their positions. Check the following settings:
1. The water floating level should stay in the range between two the red markers.
2. The floating sensor should be mounted near the bottom of the floating gauge.
3. All four floating sensors are connected in series to the safety circuit with 24V voltage. Checking the voltage between each of the sensor connctors and ground will identify the malfunctioning sensor.

Control Panel Dead. If this condition occurs, first check the main power swithc then the fuses behind the right hand door of the power supply cabinet. Replace any blown fuses and reset the main power switch to on. If all LEDs on the operating panels are unlit, the ROOM DIM knob may be in the off position.
Vacuum Leak IGP. If IGP stays abnormally high after insertion of any holder or without a holder, there is probably a small leak in the goinionmeter. If holder inserted, pull out to intermediate position and reinsert. If no holder, put one in (and take out again if desired). If cold trap is chilled, then IGP should recover relatively quickly (5 min). If cold trap not chilled, recovery would take much longer (best to chill it at this point to make sure everything ok).

Vacuum Leak P3. It occured on 8/13/96 when taking an exposure. The camera chamber vacuum reading P3 dramatically increased during a plate transport (from 52 to 72). The P3 reached 99 after three exposures and the HT & filament was shut off. The Philips service engineer Joe Maniscalco fixed the problem with following procedure:
1. Tested plate transport with and w/o plates; same.
2. Dismounted plate transport mechanism, finding no damage on O-ring or piston.
3. Cleaned and lubbed the O-ring and seats.
4. Reassembled and tested. P3 = 55 with no change during or after plate transport.

Camera Jam. When taking an exposure, the film plate may be jammed, such as what happened on 9/30/96, 10/7/96, and several other times. Do the following to correct the problem.
1. Vent the camera as you would do when change the camera. Check Basic Procedures regarding how to change the camera.
2. Remove HT cable holder from the supporter connected on the back column cover.
3. Remove the back column cover.
4. Open the left viewing chamber window glass (Caution: always wear gloves when work inside the chamber!).
5. Switch Y20.0 and Y20.1 connectors (can be reached from the back of the microscope right behind the column above the camera level) to release the force on the plates.
6. Remove the top plate. Serveral attemptes with some manipulations.
7. Reengage the plate transfer stage with the piston arm.
8. Retract the bottom plate back to the camera by switching Y20.0 and Y20.1 forth and back.
9. Switch the Y20.0 and Y20.1 connectors to the original position and put back the viewing window glass.
Comments: If the jamming is not very severe and only one plate involved, it is not necessary to open the viewing window. Simply switching the Y20.0 and Y20.1 connectors may clear the jam.