Autopsy of Old Telescope Mount

In order to convert my old GoTo telescope mount into a fully manual mount, I had to disassemble all the parts that made this mount a GoTo tracking mount.  This allowed me to more closely inspect these parts.  Mostly, this close inspection was simply out of curiosity but I also wanted to know what part(s) failed so I can help others who have this mount and encounter similar problems.  

Disassembling the motor housings was the first problem (pictured at right).  It seemed that the screws holding the clamshell motor housings together were stripped.  I could not get a screwdriver to fit well enough so I could make any headway in removing these eight screws.

Note:  I've since decided that the screw heads were not actually stripped.  I believe they were either screwed in too tightly or some sort of glue like Loctite was used to keep these screws firmly in place.  Instead, I decided to just remove the housings as a whole.  Once I had the housings off the mount with the motors and electronics tucked away inside the housings, I could more easily get at those eight screws.  As I noted above, I think they must have used Loctite on those screws during assembly for some reason.  To make it even more difficult to remove these screws is the fact that a screwdriver wouldn't fit into some of the holes because the mount itself was in the way.  Completely removing the housings was the way to go and then you can more easily remove the eight screws that hold the clamshell housings together.  

The first thing I checked was the mechanism that tells the mount where the telescope is pointed.  This is accomplished by light emitted from an emitter, shining through a wheel with many small slots around the circumference of the wheel.  As the axis of the mount turns, the wheel turns and the light flashes as it passes through these slots.  On the other side of the wheel is a receiver where the flashes of light are received.  The brains of the mount then counts the flashes of light.  I still think that part of my runaway GoTo problem that I encountered during solar astronomy was due to stray sunlight getting into the RA housing.  

Upon closer inspection of the rest of the electronics, I noticed that the two power leads coming off the main switch were kinked and the wire casings were showing signs of damage.  This also could have an effect on the performance of the mount.  

So, I could have had a stray light issue.  I could also have had an intermittent power issue due to those kinked power leads.  As if that isn't enough potential problems to find, there is one more potential problem.  

My handset contains the "brains" of the mount.  I know that my particular handset has always been a bit quirky.  I input my location coordinates...  then the next time I check the coordinates at startup, the minutes of the coordinates have decreased by one.  The next time I startup, they decrease by one again.  It does this every time.  I was just living with that problem because I could easily correct the coordinates each time but, if this was not functioning correctly, I have to wonder what else in the handset wasn't functioning correctly.  

The ROM that contains the firmware for operating the mount is filled with no memory left for more firmware code.  The firmware completely filled the ROM chip (someone else verified this).  This sort of explains or could be an excuse for the numerous odd abbreviations of words and phrases.  By eliminating certain characters, they saved a bit of much needed space on that ROM chip.  Not only would you have to figure out the odd abbreviations when using the hand controller but you would also need to decipher awkward phrases due to poor translation.

So, I hadn't pinpointed precise and proven issues with this mount but I did find a few potential issues that needed to be corrected in order to effectively use this mount as a GoTo tracking mount again.  Since I purchased a far better mount for GoTo and tracking, I felt I would be better off converting this old mount to a fully manual mount.

In the photo below, the exposed gear shown here controls the rotation of the Declination axis (DEC).  I already ordered a couple of knobs to be used as slow motion control knobs in place of the exposed gear.  I plan to change out that saddle too (the top plate that clamps onto the telescope).  Those parts are on order already.

The next photo shows the exposed gear controlling rotation of the Right Ascension axis (RA).  This gear will also be replaced with a nice new shiny aluminum slow motion control knob. 

So, this little project is coming along and I learned a bit more about this old mount.  This new knowledge and experience will help me help others who are experiencing issues with this particular old mount.  In my case, there are definitely too many 'iffy' parts to repair in this old mount to get it to be a consistently good mount.  I probably couldn't get any parts anyway.  This mount really is rather generic and, as far as functionality, precision, and current electronics, this mount could even be classified as archaic and maybe even obsolete.  

Once the new slow motion control knobs arrive as well as the new saddle, I'm looking forward to testing this manual mount under the night sky (or under the sun since most nights tend to be cloudy around here).