Author Topic: Some More Microscope Repairs - I hope!  (Read 223 times)

Offline Pete W.

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Some More Microscope Repairs - I hope!
« on: November 04, 2017, 10:29:56 AM »
Hi there, all,

Some time ago, I bought a Cooke, Troughton & Sims polarising microscope from an eBay seller.  Unfortunately, the seller didn't immobilise the insturment within the packing and it arrived damaged.  I'd bought it for the sake of some interchangeable parts that I wanted for another microscope and felt, at the time, that I'd got my money's worth.

However, the microscope in question was/is the polarising variant of CTS' top-line stand, in which the fine focus mechanism only moves the objective, not the whole tube.  Having damaged or incomplete instruments gets my fingers itching and starts a desire to repair or complete the poorly device.  So I recently investigated to see if a repair might be feasible.

The microscope must have experienced a severe shock in transit, the tube had been driven to the upper end of the coarse focus travel and then damaged the last tooth of the coarse focus rack.  That might not be too serious, one isn't always operating at the limit of travel.  I think some gentle dressing with a Swiss file may restore smooth operation there.  However, there was also damage to the fine focus mechanism.  The mounting of the objective holder to its slide had borne the brunt of the impact, shearing two fixing screws (10 or 12 B.A., I haven't measured them yet) and bending the locating pins.  I hope that you can see the damage in the first three photos.  Not only are the pins bent but their holes in the brass casting are bruised.

In order to make a bit of space, I've also picked up a long standing job, a repair to a Vickers microscope lamp.  (I've added three photos of an identical microscope lamp, #4, #5 & #6.) The damaged lamp belongs to a friend who had rescued it when his employers had discarded it and it had been thrown into the skip!!!  The lamp consists of a cast aluminium base that houses a transformer, a rheostat to adjust brightness and an on-off switch.  The actual lamp-house rides on a vertical steel pillar mounted to the outside of the base and its vertical position is locked by a clamp not dissimilar to those on a DTI Mag-base (but larger).  The lamp-house contains the bulb and has a focussing lens and an iris diaphragm - there is a ventilation grill with a light baffle on each side.  I'm starting by re-wiring the lamp-house which had been wired up with far to heavy a flexible cable - it had also lost its cord-grip.  This requires that the ventilation grills be removed to gain access to the internal electrical connections.  The ventilation grills comprise a flanged ring with both inner and outer very fine threads, aluminium on aluminium!  They screw into the lamp-house body and a locking ring screwed into the inner thread holds the expanded aluminium grill and the light baffle.  See photos #7 & #8.  My pin spanners don't have small enough pins to fit the holes in the rings so I had to use a pair of narrow-nosed pliers, far from ideal but I managed!  The lamp also suffered damage within its base - I'll return to that in a later post.   
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline seadog

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Re: Some More Microscope Repairs - I hope!
« Reply #1 on: November 05, 2017, 01:02:08 PM »
You could probably peen the metal in the distorted holes back into place. Make some new pins and drill a piece of steel rod with to be a close fit on a pin, and face the end so it's square. With a pin fitted in each hole you should then be able to tap the metal back into place.