Telescope repair update:
Last night it was clear for a couple a few hours, but my telescope was not cooperating. The declination runaway problem went from being intermittent to happening constantly. I had to give up after gathering only 20 minutes of data.
I haven't received the optical encoders yet. As a matter of fact, according to Digi-Key's website, they haven't even shipped yet.
This afternoon I saw that the forecast was clear skies all night. Gaah! it's the first fully clear night in weeks! I couldn't just twiddle my thumbs all night, waiting. I had to do
something. Anything that might help. I didn't really have anything to lose. For all I knew, a termite might have laid her eggs in the optical encoder, and all I needed to do was clean it out. I had to at least try.
So I decided to try to clean or fix the existing encoder, as long as I'm waiting for the new ones to arrive. So I carefully ripped out the declination motor assembly, and took it up to my private laboratory (pronounced lab-OR-a-TOR-ee).
Fig 4. Declination motor assembly in laboratory. Much of the hot glue that Meade put on it has been carefully stripped away with an X-ACTO knife by this point.
I had to take an X-ACTO knife and remove as much hot glue as I could. I'm not sure why Meade used the hot glue, but it was concentrated around the motor's electrical connections and the encoder's electrical connector (the one on the encoder itself). Maybe it's to prevent corrosion? I don't know, I'm guessing Meade had their reasons.
By the way, that thing to the left in Figure 4 that looks like a back-to-the-future flux capacitor is a choke coil, I assume. Presumably it's to prevent the motor's back-emf from damaging the controller board. Or maybe it's for electrostatic discharge reasons, but I'm still guessing back-emf. (Do you think it could be there to reduce RF interference caused by the motor? This scope does support GPS, so maybe it's to reduce the interference caused by the motor, with the GPS receiver in mind, maybe.)
The optical encoder is that thing on the end of the motor that has the label on it.
Btw, for those who don't know, an optical encoder is able to provide feedback letting the motor controller know how far the motor has advanced and in which direction.
Fig. 5 Theory of operation.
Figure 5 shows the basic theory of operation. The encoder that I'm working with is like that, except the encoder disk has one side completely reflective, thus allowing the LED source and the two photodetectors to all be mounted on the same side of the disk. (To be clear, one side of the glass disk has the stripes on it, and the other side of the glass is mirrored.)
Anyway, after getting rid of most of that hot-glue, I was was able to take off the encoder's cap. Everything appeared to be in working order (visually). There didn't appear to be anything I could do besides dust it off. So that's what I did with a handheld air blower. I put the cap back on. I also removed and re-seated the encoder's electrical connector that was previously covered in hot-glue.
I reattached everything back out on the telescope. Good news: it seems to work now! I don't know what I did. But maybe one of the photodetectors or the LED had big piece of dust on it or something. I'm not sure.
Before it got dark I slewed it back and forth for several minutes without problems. So far tonight I've been able to image nearly 4 hours so far, and everything is still working.
Of course, the problem
might rear its vomitus, disgusting head again. The problem was intermittent before. I just hope it lasts until the new encoder arrives. So far so good.
Edit: Oh, and
@dlgoff, I have a package of hundreds of these cable ties. I need to remove the flux-capacitor-looking choke coil everytime I remove the motor assembly, since its covering a screw I need to get to. Then I put a new one on when I reassemble. But I have plenty. I should have enough to work on the thing hundreds of times. Thanks!
Fig. 6 cable ties by the hundreds.