Problem mit z-Trieb am Leitz Diaplan

[Stevie]

Hallo Mikrofreunde,

ich habe kürzlich ein Leitz Diaplan erworben und musste leider feststellen, dass dieses einige Mängel hat. Das gravierendste Problem ist, dass sich der Objekttisch nicht richtig hoch fahren lässt, so dass es praktisch unmöglich ist, ein Objekt auch nur in die Nähe der Objektive zu bringen bzw. zu fokussieren. Anbei ein Foto mit einem 100x Ölobjektiv (45mm Abgleichlänge), das den unmöglichen Abstand zu einem Objektträger verdeutlicht. Normalerweise müsste das Ölobjektiv ja (fast) in Kontakt mit Deckglas auf dem Objektträger kommen. Hier liegen noch etwa 2 cm dazwischen. Im Übrigen kann man auch den Kondensor nicht entnehmen, da sich der Objekttisch nicht weit genug hochfahren lässt.

Also, aus unbekannten Gründen lässt sich der z-Trieb (Fokustrieb) an einem bestimmten Punkt einfach nicht weiter höher drehen. Es ist ein klarer Anschlag zu spüren und der Feintrieb beginnt langsam rückwärts zu drehen, wenn man versucht den Grobtrieb noch höher drehen. Es scheint fasst so, als wäre die Fokusstop-Funktion aktiv. Allerdings spielt es keine Rolle, ob ich die Schraube für den Fokusstop locker oder fest drehe. Der Anschlag bleibt. Mache ich dabei irgendwas falsch? Vielleicht können mir die Diaplan-Experten unter euch da einen Tipp geben?

Meine Befürchtung ist natürlich, dass tatsächlich die Mechanik irgendwie beschädigt/festgefressen ist. Kann man dies selbst beheben? Weiß jemand wie bzw. wo man was öffnen kann, um an den z-Trieb zu kommen bzw. die Lage zu checken? Gibt es irgendwo eine Wartungsanleitung?

Im übrigen quietscht der z-Trieb auch, wenn ich die Höhe im noch nutzbaren Bereich mit dem Grobtrieb verstelle. Er bewegt sich hier noch recht gut, läuft aber auch nicht so butterweich, wie es eigentlich sein sollte. Der Feintrieb läuft hier ohne Probleme. Vermutlich muss also dieswegen etwas neu geschmiert werden.

Ich wäre für jede Hilfe dankbar.

[BentH]

Hi,
The stage carrier can be mounted in 2 positions, high and low. Check that it is mounted in the right position. If that is not the explanation, the rack and pinion has been been mounted wrongly.
It has probably been disassembled for cleaning and lubrication by an unskilled person.
Regards,
Bent

[Stevie]

Hi Bent,

that sounds interesting. How do I change the mounting position of the stage carrier?

I also measured the traveling range that my stage currently has. It is only around 5 mm. According to the manual, the traveling range should be 25 mm. The missing 20 mm is roughly what I would need to reach my specimen/slide with the oil objective.

It is also strange that the focus stop knob seems to have no effect at all. I guess it should be working even if the stage carrier would have been mounted in the wrong position.

Kind regards,
Steve

[BentH]

I have done 3 Diaplans. They all had a stuck focus stop mechanism due to hardened grease. It could be corrected with generous use of WD40. I don't know how it works, and I think it could be your only problem. Otherwise you may have to remove the stage and the condenser carrier. Then you can unscrew the 4 unbraco screws that fastens the stage carrier to the focusing mechanism. In the forusing mechanism you will see 8 holes that let you mount the stage carrier in 2 positions.
The short travel of the focusing mechanism suggests that the problem lies here. As the microscope is probably 30-35 years old, it is probably filled with dried up grease, and it would benefit from a good clean and fresh grease. It takes some guts to disassemble the focusing mechanism and to get it back in a working condition. If you are not bold and brave, you could give the whole mechanism a good spray with WD40. That could loosen up things without disassembly.
Have fun !

[Stevie]

I managed to get the Focus Stop function working again. Apparently, the rotary knob was only fixed at a wrong position on the axle shaft (with the two tiny grub screws) such that it could never fix the corresponding gar wheel below. Hence, the Focus Stop remained disengaged irrespective of the direction in which you moved the rotary knob. Now that this problem is fixed, I can engage and disengage the Focus Stop on any z-height below my maximum z-height.

This raises the question, if it is not the Focus Stop, what limits my z-height to just 5 mm (approximately)?

I managed to remove the stage and took a look at the focusing mechanism, where the stage would be attached. Apparently, the stage was already mounted in the correct (upper) position/height. The distance between the to 2 positions is only 7 mm and thus would not be enough to explain the missing 20 mm in z-height anyway.

I attached a picture. Maybe you could have a look and tell me if you can see anything else that could be mounted wrongly. The focusing mechanism is moved has high as possible in this picture.

It is kind of strange that the stop/impact, when I move the focus as high as possible, feels really "solid" and abrupt, as if the mechanism would be bumping into something. If I would not know better, I would say this feels as the mechanical limit of the slider. Which is really strange...

[BentH]

I cann't see what is wrong, but now I know. Take a deep breath, disconnect the 2 springs and remove the 8 unbraco screws in the focusing rails with the microscope lying on the back. With luck you can remove the whole focusing assembly without losing the rollers. when you do that, you will disconnect the rack and pinion. Now you have to find the right position for reassembly. It may take some experimentation. The 2 springs will have disappeared in the mounting holes. They are easily picked up again with a small wire hook.
First, take a look at the rollers. They are best kept in place if they are lubricated with a lot of grease.

[BentH]

Another word of advice. The microscope is 30-35 years old. The build-in power supply is fitted with a lot of eletrolytic capacitors with a life expectency of 30 years. There is a good chance that the power supply will blow up when you start using it. Unfortunately the printed circuit board is not high quality, and there is a good chance that the circuit board will be damaged if you blow a capacitor. You could save yourself from a lot of annoyances by giving the curcuit board a thorough inspection looking for discolored and deformed components. I myself has chosen to replace all elecrolytic capacitors. They are all small capacity and replacements are cheap.

[Diana1982]

Hallo Stevie,

Das Problem mit der Elektronik, das Bent beschreibt, kenne ich leider auch zu genüge...
Aber etwas anderes: Falls Du mechanisch nicht alleine weiterkommst - ich kann das DIAPLAN-Getriebe für Dich überholen, so dass es wieder geschmeidig läuft und der Tisch in richtiger Höhe sitzt.

LG Diana

[deBult]

Another word of advice. The microscope is 30-35 years old. The build-in power supply is fitted with a lot of eletrolytic capacitors with a life expectency of 30 years. There is a good chance that the power supply will blow up when you start using it. Unfortunately the printed circuit board is not high quality, and there is a good chance that the circuit board will be damaged if you blow a capacitor. You could save yourself from a lot of annoyances by giving the curcuit board a thorough inspection looking for discolored and deformed components. I myself has chosen to replace all elecrolytic capacitors. They are all small capacity and replacements are cheap.

This ElCo capacitor issue is common in all older electronics (e.g. older tube amplifiers etc.): often a life span of only 10 years is quoted (temperature is an important factor here)
My personal strategy (mainly working on Olympus BH2) is to replace the ElCo capacitor(s) and for the replacement select a version with higher temperature specification).

Best, Maarten

[BentH]

Leitz has made many fine things. This power supply is not one of them. Last time I did a Diaplan, I replaced the power supply with a dimmable halogen supply from OSRAM (Halotronic HTM 105/230-240). It fits nicely in the microscope stand mounted on a simple bracket. A suitable dimmer can be obtained from swedish BILTEMA. I don't know if BILTEMA is represented in Germany, but the danish link to the dimmer is here https://www.biltema.dk/byggeri/elinstallationer/dampere/led-dimmer-2000041822 . The dimmer can easily be disassembled and it is mounted in a single hole. After cutting the cooling fins of the dimmer it can replace the potmeter of the microscope. By pushing the knob, you turn the light of and on, by turning the knob you change the light intensity. The OSRAM units output cannot be measured with a simple AC/DC voltmeter. I assume it supplies an oddly shaped AC voltage. However the halogen bulb seems quite happy, so why bother ?
I think any microscopist will benefit from the experience of disassembling and reassembling a focusing mechanism to working condition. It is great fun, If you fail you will better appreciate the skills and knowledge of Diana, who I know is very helpfull and knowledgeable.
Has anybody any idea why Leitz got the stupid idea of moving the aperture diafragm from the condenser to the microscope stand in this microscope ?

[Stevie]

Thank you all for your feedback and particularly Diana for offering practical help. I the meantime, I received word from the vendor who is willing to check/repair the microscope or take it back.

Has anybody any idea why Leitz got the stupid idea of moving the aperture diafragm from the condenser to the microscope stand in this microscope ?

Yes. According to a Leitz brochure: "For the first time in microscope design, and in contrast to all conventional condenser systems used so far, the aperture diaphragm has been taken out of the condenser and installed in the base of the microscope. The diaphragm is therefore fully effective also with objectives of low primary magnification, i.e. its function for the regulation of the contrast, of the depth of field, and of the resolution of the microscopic image can be effective without limitation. This is pf particular advantage in photomicrography."

Kind regards,
Steve

[JMB]

Liebe Diaplan-Bastler,

ich bin im Besitzt eines Scans des Diaplan-Servicehandbuches. Wer daran Interesse hat, dem kann ich die Datei gerne zusenden (31 MB). Mir einfach kurz eine PM mit einer E-Mail Adresse schicken.

mit freundlichen Grüßen,

Jens

[Stevie]

Das Angebot nehme ich gerne an. PM ist unterwegs.