Jump to content

Sketches

Star Adventurer Tuning


Thalestris24
 Share

Recommended Posts

Hi

I'm looking at my old SA with a view to maybe resurrecting it... It has never worked properly - at least, not to my satisfaction...

Has anyone ever stripped out the block that holds the motor and gears? I can't see an easy way of doing it (I'm probably missing something obvious).

There seems to be quite a bit of backlash in the motor gears which I reckon could be minimised. I made a quick video

I have a sneaky suspicion that I'll have to undo the polarscope in order to remove the motor + gears en bloc?

Thanks for any help :)

Louise

Link to comment
Share on other sites

Ok - I figured it out! :) Wasn't difficult...

Anyway, you just need to take off the Dovetail holder, then the RA mechanism, then undo 2 hex bolts et voila!

1)

Taking the dovetail holder off reveals 4 hex bolts

SA_undo_1.jpg.d706980abb3296ddeb392cda66a4e308.jpg

 

 

2) Then the RA clutch mechanism and gear comes off. Then just undo the two hex bolts under the polarscope. One of them was very tight on mine!

SA_undo_2.jpg.e043e44153241736910c8d8d8139e180.jpg

 

3)
SA_undo_3.jpg.046f76ae155645d77c48140d0164975f.jpg

Hopefully, I 'll be able to adjust the backlash now. Will it ever work well? We'll see.

Louise

  • Like 4
Link to comment
Share on other sites

1 hour ago, Thalestris24 said:

I did the motor adjustment ok. Had a go at adjusting the worm but that was not a very positive adjust - it seems worm drives never are!

 

Hi Louise watching with great interest after all the problems I am having on the other blog where I found this link. Good luck Alec

Link to comment
Share on other sites

11 minutes ago, alcol620 said:

Louise are you re-greasing as well?

 

Hi

Um, I wasn't going to bother. I don't think it needs much and there's probably enough still there. I have to do a small electronics mod (adding a 2.1mm socket for 5V). Then I'll put it all back together and give it a test :)

Louise

ps will finish it tomorrow

Edited by Thalestris24
  • Thanks 1
Link to comment
Share on other sites

2 hours ago, Thalestris24 said:

Hi

Um, I wasn't going to bother. I don't think it needs much and there's probably enough still there. I have to do a small electronics mod (adding a 2.1mm socket for 5V). Then I'll put it all back together and give it a test :)

Louise

ps will finish it tomorrow

fingers crossed

  • Like 1
Link to comment
Share on other sites

Here is a pic of my SA pcb. Should anyone have any interest, I've figured out what most of the ic's are:

PCB_crop.thumb.jpg.6bacc224bd5d4c2601ea64c51d051465.jpg

 

U1 is a 1502 programmable logic array - 'the brains'

U2 is a 352 optocoupler

U3 ? (managed to skip that one... It's probably a linear device to do with the motor control)

U4 is a 6552 Motor driver

U5 is a LD1117 low dropout voltage regulator - anything slightly over 5V is regulated to 5V which is probably how the nominally 6V batteries last so long! It can supply up to 800mA

U6 is a PL2303 Prolific usb-serial bridge controller. Presumably only used for upgrading the firmware in the 1502

So not much to it really :)

My usb/5V input seems to be working now :D All put back together for (initial) testing :) 

Louise

 

  • Like 2
Link to comment
Share on other sites

Given that the firmware can be updated, in theory at least one might expect that if the drive rate were a little out (ie. not as close to sidereal rate as desired) it might be possible to patch the firmware to fix it.

In practice, could be a bit tricky however :)

James

Link to comment
Share on other sites

6 minutes ago, JamesF said:

Given that the firmware can be updated, in theory at least one might expect that if the drive rate were a little out (ie. not as close to sidereal rate as desired) it might be possible to patch the firmware to fix it.

In practice, could be a bit tricky however :)

James

I think life's too short ha ha

Link to comment
Share on other sites

I did a quick Sidereal Day test earlier though I cheated, hee hee. I ran it at the 12x speed which meant it completed one revolution in 2hrs. It was pretty spot on so that was reassuring. Maybe one of these days, in the not-too-distant future I'll get some clear enough skies that will let me test it properly. Fingers crossed!

Louise

Link to comment
Share on other sites

Hi Louise..you have far more bottle than what I have to open it up and have a dabble..are you some sort of electronics geek...those boards just look the same to me,let alone find out what they do..

A friend opened his up but said there wasn't any adjustment on the gears? Maybe he ment the worm...but we'll done for doing it although not re-greasing while you have a chance just seems criminal..

Link to comment
Share on other sites

17 minutes ago, newbie alert said:

Hi Louise..you have far more bottle than what I have to open it up and have a dabble..are you some sort of electronics geek...those boards just look the same to me,let alone find out what they do..

A friend opened his up but said there wasn't any adjustment on the gears? Maybe he ment the worm...but we'll done for doing it although not re-greasing while you have a chance just seems criminal..

I have some electronics knowledge :) It was a case of having to open it up but, as astro equipment goes, it's not that expensive and it had been gathering dust more or less since I bought it 3 years ago. So nothing to lose! There isn't much of a load on it so not much grease required, I don't think. There's only one bearing which kept it's grease. In normal use it only moves really slowly so I don't think the grease is that important - just a little required. Now I know how to undo it, I could easily go back and add some grease should I ever feel it's necessary. The above 2hr 12x test was fine, so that was encouraging.

There are two screws which hold the motor in place. By slackening them off you can move the motor to minimize backlash. As I mentioned, you can only get to the second motor screw by undoing everything. There is a hex nut which slackens off the worm gear and an adjuster next to it. I decided not to adjust the adjuster! I hate worm gear adjustment! There is noticeably less play in the RA axis now. I posted a video showing the play in RA 3 years ago but then just put it to one side... I might, possibly, get a chance to give it a test tonight but I'm not holding my breath on that!

Louise

Link to comment
Share on other sites

Gave it a quick test last night with a 75-300mm lens set at 75mm. Seemed to give ok 60s images at first sight but close up the stars weren't so good. But I only did a guesstimate PA so that could have been quite out. Today I did a bit of diy and drilled some aluminium bar to fit in place of the counterweight bar. That's allowed me to attach a guidescope so will try that out in the hopefully, not-too-distant future...

Louise

Link to comment
Share on other sites

Well done Louise, great stuff. You have encouraged me to have a go at the SA as well. Currently in pieces on the dining room table, while I read this and other posts before I start adjusting things

Fingers crossed

Link to comment
Share on other sites

  • 1 month later...

Hi Louise,

Just read this post adn couple weeks ago I also decided to open up the SA and found exactly the same backlash on the gears as yours in the video.

Tried to adjust the gears and I believe it now has less backlash but it is still there. It also looks from your video that the smallest gear is "bad aligned" . Mine was positioned more on the inside. Not aligned with the gear next to it. I had to take out the motor to change the 2 screws holding the little gear. 

Tests showed that it didn't change much and still had the same accuracy as before. Did you managed to get rid of the backlash somehow?

Ken

Link to comment
Share on other sites

13 minutes ago, Ken Mitchell said:

Hi Louise,

Just read this post adn couple weeks ago I also decided to open up the SA and found exactly the same backlash on the gears as yours in the video.

Tried to adjust the gears and I believe it now has less backlash but it is still there. It also looks from your video that the smallest gear is "bad aligned" . Mine was positioned more on the inside. Not aligned with the gear next to it. I had to take out the motor to change the 2 screws holding the little gear. 

Tests showed that it didn't change much and still had the same accuracy as before. Did you managed to get rid of the backlash somehow?

Ken

Hi

I think I improved things but I seem to remember it was still far from as good as I hoped it would be. Not done anything with it for a long time. I get very few opportunities to do any kind of imaging here cos of the weather/poor sky conditions

Louise

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.