Leitz pol condenser

ChrisR · Post by **ChrisR** » Sun Dec 10, 2017 4:44 pm

This is from an HM-Pol microscope.

I believe the lowest, knurled ring, which holds the polariser, should rotate. It doesn't, so I think it may be seized.

Can anyone confirm, refute, or suggest how to unseize it?

Red is the flip-top knob
Blue centralise
Cyan screws (3x) allow that ring to turn - it only has an index mark.
Green knob tightens and loosens itself but apparently does nothing
Green knurled ring which maybe should turn, doesn't turn. I tried loosening small green arrowed screw. There's only the one screw on that ring.

I haven't tried removing the pol filter itself, from the underside.

Ichthyophthirius · Post by **Ichthyophthirius** » Tue Dec 12, 2017 5:20 am

Hi Chris,

From what I gather this is a very common problem with the series 700 pol condensors.

First of all, you should be able to swing out the pol tray like this: https://i.ebayimg.com/thumbs/images/g/n ... s-l225.jpg This won't help you with the rotation but gives you a look from the top. Try gently.

The green curdeled ring is the clamp for the rotation of the polariser. It needs to be loosened.

The small cyan grub screws are part of the assembly. They need to stay in.

The most common cause of problems is that the rotation mechanism is ceased up with old gummed grease. If you are lucky, you can re-mobilise the mechanism. Warm the condenser very gently at 40 C in a dry atmosphere. Check with a thermometer!! At much higher temperatures the plastic polariser can be damaged.

Wait a few hours and try to gently turn the ring (green curdled ring). If that doesn't work, add a few microlitres (micro!) of petroleum ether in the gap and try again.

Avoid WD40. It may mobilise the ring for a while but if you don't remove all of it it will gum up even worse.

Regards, Ichty

ChrisR · Post by **ChrisR** » Tue Dec 12, 2017 5:47 pm

Thanks Ichty.
Knowing it was supposed to rotate, I use a lot more force, and it rotates now.

.
I expect it'll seize up again though so it would be good to regrease it.
I don't think my model swings out - it's slightly different. I'll do another picture.

Eddie · Post by **Eddie** » Wed Dec 13, 2017 10:30 am

If you can rotate it now, it would be a good idea to unscrew if from the mount and clean it. I believe that the circular hole on the bottom exposes the three screws, as you rotate it, which holds it in place