NATIONAL 400 (01) PDF Document

Stereoscopic microscopes are used for viewing 3-dimensional objects, inspection or assembly of small parts, and for dissection of biological specimen. They provide an upright, unreversed image which permits easy manipulation of the object being viewed while looking through the microscope. They are designed for viewing solid objects at low magnification, but they will also permit viewing of some transparent specimen slides.

The only difference is that the NATIONAL 400 series has a vertical viewing head (eyepieces are straight up and down) and the NATIONAL 405 series has a 45 degree inclined viewing head. The inclined viewing head permits more comfortable viewing angle when user is seated.

Microscope magnification is determined by multiplying the number on the eyepiece times the number on the objective lens. These numbers are incorporated in the model number of your particular microscope purchase.

A NATIONAL 400TBL-10-2 has 10x eyepieces and 2x objectives, which provide 20x magnification.

Model 400-10-2 (no illumination) is available only with the 2x objective option, and since the 2x objective is fixed permanently in place, there is no 2x marking on the objective.

The magnification chart for illuminated models is as follows:

The magnification chart for non-illuminated models is as follows:

If your NATIONAL 400 model is not supplied with built-in illumination, it should be used where adequate natural or overhead light is available.

To install optional #903 penlight illuminator:

Step 1. Remove chrome lamp holder and lamp assembly from body of penlight by rotating lamp holder in a counter clockwise direction. Remove white plastic tube from penlight (discard white tube) and insert 2 each AAA batteries into body of penlight (positive terminals facing up toward lamp). Replace chrome lamp holder and lamp by screwing tip in a clockwise direction.

Step 2. Insert penlight into black rubber lined friction mounting port located immediately behind head of microscope.

Determine whether the black or white side of the stage plate will provide best contrast with the specimen to be viewed. The white side will be used for most viewing. It will always be required when viewing transparent specimen slides because it better reflects light through specimen slide.

To reverse black/white plate, loosen locking set screw located at front of base with “L” hex wrench provided. Insert plate with selected surface facing up. Tighten locking set screw.

Three switches are on top of base:

Step 1. Main power on/off.

Step 2. The “I” switch controls incident (top) light.

Step 3. The “T” switch controls transmitted (bottom) light.

FROSTED GLASS PLATE MUST BE USED IF USING BOTTOM ILLUMINATION. HEAT GENERATED IN BASE FROM BOTTOM LIGHT WILL WARP OR DAMAGE THE PLASTIC BLACK/WHITE PLATE. SUCH DAMAGE WILL NOT BE COVERED BY WARRANTY. It is acceptable to leave the glass plate in place for most viewing purposes.

The black/white contrast plate can be used when viewing opaque objects or for dissecting. Choose side of plate providing best contrast with specimen. Remember, do not use bottom light with this plate in place.

This permits each user to adjust spacing between eyepieces in order to accommodate distance between their eyes. Observe that each eyepiece tube on each side of microscope head is mounted on its own gray metal housing. While looking through microscope, use both hands to firmly grasp gray metal housing and gently pull or push the sides in a horizontal path until images viewed through both eyepieces appear as one and field of view appears as one circle of light.

Place object or specimen slide in center of stage plate.

The viewing head is mounted on a post, and height of head can be adjusted up or down on post in order to focus on difference sized specimen. Loosen the post locking knob located on back of focus block so that viewing head can move freely up or down on post.

While looking through microscope, move head up or down on post until image is in approximate focus. Tighten post locking knob. It is not necessary to make this adjustment every time you change objects being viewed, unless there is a significant difference in thickness or height of objects.

Rotate focusing knobs with both hands until specimen comes into sharp focus in right side of microscope.

Because most people have some difference in vision between the left and right eye, your microscope is equipped with a diopter adjustment on the left eyepiece to compensate for this difference and assure that you will see one corrected image when looking through microscope.

Observe that the knurled diopter ring on the left eyepiece tube can be rotated to move the eyepiece up or down slightly. When a silver ring on the eyepiece tube is visible just below the diopter ring, the focus of both sides of microscope is matched for 20/20 vision.

If you do not have 20/20 vision, turn knurled diopter ring until left side of microscope is also in sharp focus. Left and right images should now blend into one focused image. The microscope is now adjusted for your vision, and no further adjustment of the diopter should be required. Only the focusing knobs will require further adjustment when viewing objects of different thickness.

For your own safety, turn switch off and remove plug from power source before maintaining your microscope. If the power cord is worn, cut or damaged in any way, have it replaced immediately to avoid shock or fire hazard.

Do not attempt to disassemble any lens components. Consult a microscope service technician when any repairs not covered by instructions are needed.

To clean eyepiece lenses, do not remove from eyepiece tube. Clean only the outer lens surface. Breath on lens to dampen surface, then wipe with lens paper or tissue. Avoid wiping dry lens surface as lenses are scratched easily. If excessive dirt or grease gets on lens surface, a small amount of Windex can be used on a cotton swab or lens tissue.

To clean objective lenses, do not remove objectives from microscope. Clean front lens element only, following same procedure [as for eyepieces].

The only mechanical adjustment you might ever require is the tension of the focusing mechanism. This has been adjusted at the factory, but over the course of time it may loosen and cause the head of the microscope to slip downward on the focusing block.

To adjust, observe that stem of focus knob on one side of microscope has a tension adjustment collar with four small holes. Only one of these holes contains a small set screw. Using a small jewelers screwdriver, loosen this set screw. Your microscope was supplied with a small pin spanner wrench having one prong. Insert pin of the wrench into one of the holes, turn collar clockwise to tighten tension, counter-clockwise to loosen tension. In the event you have misplaced the wrench, a large rubberband placed around the collar will permit you to grip the collar and turn it by hand in order to accomplish the same adjustment. After adjusting, tighten the small set screw to lock collar in place.

NOTE: It is recommended that you leave the tension as loose as possible for ease of focusing, yet not so loose that it permits the head of microscope to drift downward from its own weight and cause the microscope to “drift” out of focus.

To clean metal parts, use a clean, damp cloth to remove dust or dirt from surfaces. Then, completely dry surfaces with a dry cloth.

For your safety, turn switch off and remove plug from power source before maintaining your microscope. Wiring and transformer contained in base of illuminated models should be repaired only by qualified technicians.

To replace top light (TL & TBL models only), you will require National part #800-400, 12v 10 watt tubular bulb, or bulb of exact same specifications from other microscope manufacturers.

Step 1. Remove knurled lamp retaining screw, located on side of top lamp cover, and remove cover from lamp.

Step 2. Remove lamp from pressure clips by pulling straight out.

Step 3. Holding new lamp with tissue or cloth to avoid getting body oil on lamp, push into pressure clips.

Step 4. Replace lamp cover and secure with knurled lamp retaining screw.

To replace bottom light (TBL models only), you will require National part #800-400, same as above.

Step 1. Remove stage plate and observe lamp held in place by pressure clips in base.

Step 2. Carefully grasp bulb and remove from clips by pulling straight out.

Step 3. Holding new bulb with tissue or cloth to avoid getting body oil on lamp, push into pressure clips.

Step 4. Replace stage plate.

The fuse is located at rear left side of microscope base. To remove fuse from holder, insert a 6mm screwdriver blade into slot located in rear of fuse holder cap. Slightly depress and rotate screwdriver 1/2 turn in direction of arrow, release pressure on screwdriver to release the fuse. Pull cap and fuse out of fuse holder. Insert proper fuse into fuse cap. Insert fuse cap into fuse holder. Using screwdriver, rotate fuse cap assembly in opposite direction of arrow until guide slot engages, depress fuse cap and rotate 1/2 turn to lock into holder.

If the light fails to operate on NATIONAL 400 TL & TBL models, check the following reasons and solutions:

If the outlet is inoperative, have qualified service technician repair outlet.

If the AC power cord is not connected, plug into outlet.

If the lamp burned out, replace lamp.

If the fuse is blown, replace fuse.

If the head of microscope drops from its own weight, the tension control needs to be adjusted.

If poor resolution (image not sharp) occurs on the NATIONAL 400:

If objective lenses are dirty, clean objective lenses.

If eyepiece lens is dirty, clean eyepiece lenses.

If spots appear in the field of view on the NATIONAL 400:

If the eyepiece lens is dirty, clean eyepiece lenses.

If spots in field of view result from dirt on inside of eyepiece, it is recommended that you have service technician clean inside of lens.