This is very common. The grease in the fine focus assembly has
hardened to the consistency of glazing putty.

I have never opened a 15, but will "some time in the future." By and
large AO designs are very good and easy to work with if you record
where everything came from. Work in a baking pan to keep ball
bearings from running away. If you have ever rebuilt a car engine or
devarnished a carburetor, you are well qualified for the job.

There are very few hidden access points. The first you will encounter
is how to get the coarse focus knobs off. This is done by grabbing
both knobs and turning them forcefully counterclockwise with respect
to each other. The bearings and bushings in the knobs that you will
discover when you get one knob off are more complicated then you might
imagine. If they don't intimidate you, then keep going. Keep a pad
and pencil with you and record everything. You will be on your own.
I have never gone farther than that with a 15. Reassembly will be
close to impossible if you don't record where everything goes and most
importantly the order in which they go. Shafts will have a surprising
number of washers and bushings on them.

After disassembling, the rest is cleaning, regreasing and
reassembling. The cleaning can take hours or days. Use whatever
toxic substance you are comfortable with. I am conservative and won't
go farther than rubbing alcohol (the higher percentage version).
Xylene (lighter fluid) is mentioned a lot in this group. The grease
to use for regreasing can be debated endlessly. If you want to spend
a lot, go with nye greases ($90 for 10cc of grease in each of 5
viscosities from TAI at http://www.lubekits.com/?load=grease). If you
are cheap like me, go with an automotive grease. I recommend sta-lub
marine boat tralier grease SL3121 from CRC. It claims no volatile
organic compounds and is about as odor free as these things ever get.
You can get it at small parts Inc. http://www.smallparts.com/ under
Adhesives & Lubrication->grease for about $5 for 14oz. plus shipping.
It doesn't mix well with other greases (for example lithium greases)
so make sure your cleaning is thorough. Lithium grease would also be
fine, but they tend to be more volatile. CRC does make a low
volatility lithium grease (white grease SL3151 from same place) but it
is not zero volatility and does have slightly more odor than the
marine grease. It is more familiar in that it is like the stuff you
get for car door latches. It is hard to find other companies that
give as much data as CRC, so while there might be better greases out
there for as little money (among the half million commercial types
available), I would have no idea how to find them. The nye greases
come guaranteed as appropriate for the use.

If you do this, let me know how it went.



--- In Microscope@yahoogroups.com, "lobsterboy582000" <artzad@...> wrote:
>
> Hi all-
>
> I've aquired a Spencer 15/35 series binocular microscope with
> non-functioning fine focus.
>
> The knobs are apparently disengaged: they turn freely but do not effect
> focus.
> The assembly lifts and drops smoothly about 1/8".
>
> Guessing this is not unusual for these old scopes, if anyone would care
> to suggest a course of action: is it 'off track' somehow, or what do I
> remove for a better look, I would appreciate it.
>
> I put up a picture in album 'Spencer Series 15 with ailing fine focus'
>
> Thanks
> Art
>