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Astrotrac tt320x ag friendly word of advice regarding servicing!!


MrZuiko
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Hi all,

Just had an email from Mr Richard Taylor,managing director Astrotrac limited regarding the above tracker,mine wasn't powering up from the 8 AA cell battery pack.....read online that you could also power it by a 12v car cigarette lighter ,so you can imagine to my horror a couple of seconds of plugging in and a few whisps of smoke........cut  along story short........Astrotrac no longer offer a repair service for these units as it was discotinued in 2018 and superseded by their 360 model and have no replacement parts available.

I did reply asking Mr Taylor if he could identify the burnt component in the unlikely  event I could source a replacement and solder  a new one back on if it's that easy!!

So ladies and gents please look after them and don't plug them into  your cars cigarette socket or your have a circuit board like mine!!  not sure what I'm gonna buy now  to replace this with I've had Skywatcher SAM and the mk1 adventurer any suggestions only require it to hold my Nikon D800 and telephoto lenses nothing bigger than 300mm....

Clear skies all.

 

Ash.

astrotrac board.jpg

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  • 2 weeks later...

Looks like a tantalum capacitor.

They do have a tendency to go wrong spontaneously and in doing so normally go short circuit.

I can pop the cover off mine to see what value it should be if you're considering repairing it?

Depending on where it is in the circuit it may be sacrificial and protected the rest of the circuit, fingers crossed.

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Hi Stuart,

First apologies for the late reply !

That would be great if you could help me idenify the  part,I did email the managing director again asking for his help  with this matter but got no reply there!

I would like to try and get this working,I even had a crazy idea of connecting a speeed regulator and a reversing switch etc to see if I could spark it in to life.....but your idea sounds the best option.

Fingers crossed it's worth a punt!!

I wait your reply with interest.

 

Thanks Ash.

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Hi Ash,

Finally managed to get a photo of the PCB.

Looks like the capacitor that was damaged is a 47uF, 16V surface mount tantalum capacitor. The fact that it is rated at 16V doesn't leave much room for margin if the unit was powered from anything other than 12V DC. Power is fed through an "idiot" diode coming from the 8 pin header so incorrect polarity shouldn't have been an issue.

Was the unit plugged into something and using the guiding port (the RJ-45 connector) at all? That could have been another path for things to have gone wrong.

The stepper motor is controlled by the Allegro A3984 using a tangential pulse speed that changes over time depending on how far away the head is from the start position to achieve the tracking accuracy. I did some investigations a long time ago on how it all works.

 

PCBLayout.thumb.jpg.ca182bce320678670e92e9041edece39.jpg

Edited by StuartJPP
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Hi Stuart,

Thanks fella for getting back to me and the picture sure does help! now to find a replacement....so far I've found some but the numbers don't match on the casing (475,16R,128)...is it critical that the numbers match up?I had no joy with the 8 AA cell battery pack hence why I tried the 12v cigarette lighter route as I understood it could be powered this way...how wrong was I!

 

Regards Ash.

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Hi Stuart,

Quick update I have found on ebay a seller with a 47uF, 16V surface mount tantalum capacitor but with these case markings......476,16R, 907 not 128!

I have sent a message and photo to them so hopefully I'll get some good news!

Watch this space....pun intended!

Ash.

Edited by MrZuiko
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Hi Ash,

Do you have a multimeter handy?

It would be useful to measure across the capacitor in continuity/Ohms mode to confirm that it is a short, then remove the capacitor and measure again to see if it has gone.

Definitely make sure you're not powering up with anything more than 12V. Can also use a 100uF capacitor as well if they are available.

 

If possible check to see if you can get a 25V capacitor instead of a 16V one, might help going forwards though obviously in the same footprint and height.

I'll have a look in my "bits" box and see what I've got but I don't think I've got many tantalum capacitors at all. If I do I could pop one or two in the post.

If there was space, other types of capacitors could have been used but it is quite a tight fit in there and I doubt you'd get the top lid back on with anything more bulky.

Edited by StuartJPP
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Hi Stuart,

No multimeter I'm afraid......I've  ordered  a bunch of 16v tantalum capacitors that I have found on Ebay and give that a try.......I'm hoping that it will be that easy !!

Thanks for your help so far really appreciate it.

Ash.

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Another update lol......just whipped out my pcb  and the capacitor donesn't match yours! I've got 476c and 30ju2 on mine so I'm guessing it's a "c" size not "d" I'll have to search again for the correct size!

I have found these on Ebay TANTALUM CHIP CAPACITOR 4.7uF 25V 10% Case C KEMET T491C475K025AT PACK of 25

 

Ash.

my pcb.jpg

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Hi,Seem to be going round in circles...I've had to cancell the order as I made the mistake of ordering 475 and not 476c not having luck luck online apart from ordering from China which of course will be on a slow boat and not a speed boat!!

Not finding a UK supplier as I require them to be 6mmx3.2mm otherwise they ain't gonna fit!

Wouldn't have thought it would be so difficult getting hold of the correct part!........so I've ordered 5 from China now just gotta wait!

 

 

Ash.

Edited by MrZuiko
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Hi Stuart,

Can I ask your advice please fella........I have solder and soldering iron  would I need to use flux or can I solder without? this is the state of my pcb now that I have taken off the burnt  capacitor to my untrained eye it looks in good condition with no obvious deep scars!!

Your thoughts please.

 

Ash.

PCB crop.jpg

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Hi Ash, do you have any solder at all? The vast majority of solder has flux infused.

You may be able to get away without using it if not but I doubt you will get a decent solder joint.

Would probably be okay to check if that is the only thing wrong.

Just remember to get the polarity of the capacitor right otherwise it will all have been in vain. Fingers crossed it was just that capacitor. Without a multimeter it's not going to be easy to do much more fault finding.

If I were you I'd get one, just a cheapie, always comes in handy.

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Hi Stuart,

Yes I have solder,not sure if it has the "flux" built in tho, so are you saying that it will be difficult to get a good join even tho it's surface mounted?

How can you tell which way it has to be mounted? these are what I have ordered surely just mount it with the lettering upwards?

I can get my hands on a multimeter what next? I'm crap at electronics but quite handy  with wood!

 

Ash.

Capacititor.jpg

solder.jpg

telescope.jpg

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  • 3 weeks later...

Quick update the capcititor's have arrived at long last and great news I've soldered the new one on was a little awkward as they are so small.......soldered the jack on to a new 8 cell battery holder and bingo I'm back in business as it's working!!!! powered on and it set itself in the home position....pressed play button again and it started tracking....pressed rewind and it rewound back to the home position so now gotta wait for a clear night!

Thanks Stuart for all your help and I to have spares capacitiors should anyone require one....lets hope not!!

Clear skies all and keep safe.

 

Ash.

 

 

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Hi Phil,

I honestly don't know as I did research what power supplies worked as stated from Astrorac themselves.....Suitable Power Supplies The TT320X­AG can be powered by any of the following: ● a car battery ● 8 x 1.5 V alkaline cells (a suitable battery holder with lead can be purchased from your AstroTrac Dealer or from AstroTrac directly) ● 10 x 1.2 V NiCAD or NiMH rechargeable cells ● a mains to 12 V DC adaptor In general, we recommend using a 12 V 7.2 Ah lead acid gel battery.

I have replaced the 8 cell battery holder,I'm just happy that I have been able to fix it.......at one point I almost threw it in the dustbin.

I took sometime to identify and purchase the required capcititor! I have seen these supplied with car the battery adapters  as shown in this picture,so can probably rule that out!

 

Ash.

astrotrac-tt-320x-ag-tracking-mount_360_446bdd250958278e556c961866cbeb0e.jpg

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Evening guys,

Quick update and my first image with the Astrotrac first time using astronomy tools and photoshop,details will be posted in the imaging deep sky section.

 

Ash.

M31 Andromeda copy 3.jpg

Edited by MrZuiko
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  • 2 months later...

That is awesome, you got it working again! I have powered mine from the outlet in my car so it must have been something wrong with the capacitor to make it fail? 

Also, I must say that I´m dissapointed to hear that Astrotrac no longer service or offer any help with these since they were a high end product (compared to other portable trackers) and cost quite a bit.

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