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Any ideas on repairing a (slightly!) blown motor board ?


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Yes indeed...  🍺🍺🍺  whoopee.....

The board arrived from Malcolm in today's post and after I plugged it in and tried the up/down buttons, the Alt motor whirred into life again !!

I've been busy all day putting it through it's paces and it's tracking and "going too" with no problems. 

It displays the co-ordinates correctly when "pushed too" as well. (These goto Dobs have dual encoders).

The only very slight glitch at the moment is that when the slew speed of the Alt motor is lowered below 5, it single steps in jerks, rather than smooth slow motion.

When I put it in siderial tracking, both motors are "ticking" quietly so it appears that the Alt can move slowly and smoothly when under auto control.

I tried "daylight" alignment on the Moon, and then it correctly slewed to Polaris and Vega as gotos.  (I was able to check in daylight using the setting circles on it, as well as the handset's "show position" function.

Malcolm and Archie have not only saved me a great deal of money, but the alternative cure of buying replacement parts was fraught with uncertainty due to the Skywatcher Goto Dobs having just been "upgraded", making it difficult to know whether a new replacement Alt board would work with my still functioning AZ board,  (and would take 4 months to obtain from China).

 

Edited by Astro-Geek
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Well I've just received a PM from the owner and he's a happy bunny... Yes it's four out of four guys Due to their personal commitments they haven't had the time to put the thing through its pace

Well it's been a busy morning... The SGL member with the damaged MC003 board had a change of heart and contacted me again to see if I would still be willing to attempt to repair  his board.  Natu

We'll it looks like we've scored another goal in extra time The first thing I did this morning was to re-flash the PICs with the same 209 hex file I originally used.  Now as the PICs were solder

Posted Images

It was a team effort.  I couldn't have undertaken the swapping out of the PIC without Archies help in sorting the code, and you also put in a lot of effort in replacing the driver and encoder chips as well. 

I have no idea why it has that glitch below speed value of 5, but the fact it aligns, goto's and tracks is the main thing.....

It's been challenging but fun, and I'm glad to have been involved in helping you out. It's what these forums are for.  To share knowledge, experience and help where we can.

 

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Hi Malcolm and Padriac,

Glad that all is restored. Congatulations Malc for your persistence and dedication.

Hopefully, if I get back to the northern hemisphere, I will get to meet you in person and enjoy a beer or two.

Meanwhile, I wish you both clears skies and warm nights.

Cheers

Archie

 

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21 minutes ago, ozarchie said:

Hi Malcolm and Padriac,

Glad that all is restored. Congatulations Malc for your persistence and dedication.

Hopefully, if I get back to the northern hemisphere, I will get to meet you in person and enjoy a beer or two.

Meanwhile, I wish you both clears skies and warm nights.

Cheers

Archie

 

Sounds like a plan, and I'm sure the beers will be on AstroGeek :) :) 🍻

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8 hours ago, ozarchie said:

Hi Malcolm and Padriac,

Glad that all is restored. Congatulations Malc for your persistence and dedication.

Hopefully, if I get back to the northern hemisphere, I will get to meet you in person and enjoy a beer or two.

Meanwhile, I wish you both clears skies and warm nights.

Cheers

Archie

 

Thanks Archie, you and Malcolm have  saved me a great deal of money, and even more importantly, saved me having to wait 4 months for the parts to arrive by slow balloon from China...... 🍺

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Well done to you all - I've been admiring your perseverance as well as your skill! There has been some great knowledge building and sharing on this thread and it deserves to be captured for future reference.

I'm afraid I took the lazy route and received my replacement HEQ5 board last week. All installed and back working, in time for a weekend of clear skies. I'm not impressed at how easy it is to blow control boards on these mounts - they may be 'entry level' but they are by no means cheap. Input voltage protection seems to me like an essential design feature at this level - you'd expect some opto-isolators at a minimum; it just seems shoddy that Skywatcher/Synta decided not to include them in the design. 

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5 hours ago, Padraic M said:

Well done to you all - I've been admiring your perseverance as well as your skill! There has been some great knowledge building and sharing on this thread and it deserves to be captured for future reference.

I'm afraid I took the lazy route and received my replacement HEQ5 board last week. All installed and back working, in time for a weekend of clear skies. I'm not impressed at how easy it is to blow control boards on these mounts - they may be 'entry level' but they are by no means cheap. Input voltage protection seems to me like an essential design feature at this level - you'd expect some opto-isolators at a minimum; it just seems shoddy that Skywatcher/Synta decided not to include them in the design. 

Thanks, and having received a message from Astrogeek I can confirm that the board is now working 100% after reflowing a solder joint on a pin of the decoder chip, so now the mount moves smoothly in all directions and at all speed settings.  

I have to agree, seeing the number of posts here and on the EQMod group reporting blown boards, or the typical no response to directions you would have thought that even the basics of reverse polarity circuits or even a quick blow fuse, either self resetting or even a single use should be included to protect the rest of the electronics.  On looking back at this, if we had replaced the PIC at the start, the cost would be no more than a couple of pounds, and in my case where my HEQ5 board was blown, 56p for two capacitors fixed the board, so it does peeve me when the manufacture, importer and retailers don't support repairs on boards that cost an average £120.

If anything, this thread shows that such repairs are possible with the combined efforts of forum members.  Without Archies expertise in processing the firmware file we would have struggled, at least until I had got answers from other forums or spent ages and ages googling for an answer.  I'm sure if Archie wasn't 1000's of miles away on the other side of the globe he would have offered to have reprogrammed the PIC the same as I did.... The logistics being that both the OP and I are in the UK which made things a tad easier.  Above all its been teamwork! 

In full transparency, even though I had said I required no payment for my part in this, the OP was very insistent, and having worked out the total costs came to £4.50 for the PIC and two lots of postage, the OP generously rounded that up to £10 for which I'm very grateful.  I shall enjoy the couple of pints of stout that will get me at my local watering hole :) 

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sorry to hijack but i'm in dire straights..

can anybody help me?

i think ive messed up one or possibly both boards trying to connect a Celestron StarSense Accessory for Sky-Watcher Mounts to me 250 goto flextube dob 

any help would be appreciated

i'm not looking for a free fix but i can get any of the shops to even discuss it at the moment 

 

thanks 

ira

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On 02/06/2020 at 16:55, malc-c said:

I can confirm that the board is now working 100%

That's fantastic!

I've been following this thread from the beginning and have enjoyed watching the situation develop. Highs and lows came and went :)

I understood the electronics side but the code and programming stuff went right over at great altitude. Still, I never doubted a successful outcome!

Well done all! 

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13 minutes ago, Paul M said:

 

I understood the electronics side but the code and programming stuff went right over at great altitude. 

 

LOL - to be honest, whilst I understand the basics, a lot of what Archie took me through with the conversion of the files and using python scripts from the command line was over my head too :) 

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34 minutes ago, palatine said:

sorry to hijack but i'm in dire straights..

can anybody help me?

i think ive messed up one or possibly both boards trying to connect a Celestron StarSense Accessory for Sky-Watcher Mounts to me 250 goto flextube dob 

any help would be appreciated

i'm not looking for a free fix but i can get any of the shops to even discuss it at the moment 

 

thanks 

ira

Ira, it might be worth starting a new thread for this... if you can include more information as to what you plugged in where, to what board, if both boards were connected at the time, and what actually happens when you connect the handset it will help.  Are you able to check the board for any obvious damage?

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29 minutes ago, malc-c said:

Ira, it might be worth starting a new thread for this... if you can include more information as to what you plugged in where, to what board, if both boards were connected at the time, and what actually happens when you connect the handset it will help.  Are you able to check the board for any obvious damage?

This Is my original post. I will write at length what I experienced later. 

Thanks 

ira 

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  • 2 months later...

Dear Malcolm and Archie,

I found this topic with Google when my HEQ5 failed after a Comet NEOWISE expedition up in the mountains. With the help of your posts, I was able to repair my mount and I would like to shortly summarize how I did it.

So, it started when I turned on the mount one week later, and the hand controller said: "No response both axles"

I like to build my own PCBs and Arduino / ESP projects, so I am a bit familiar with electronics. I took the mount apart and after I traced the power supply, checked the capacitors and it was all OK, I suspected, that the serial communication of the microcontrollers should be faulty. But the mount was still under the 5 year warranty, so I decided to return it before I take out my soldering iron. Unfortunately the shop told me, that the warranty is void, because I installed a belt kit earlier what I purchased from them. (Nice...) So, I had the option to buy a new panel for ~180 EUR or fix it. I ordered the PICs and the motor controller ICs for about 20EUR total, plus a PICkit3 clone and a SOIP28 to DIP28 adapter for a few euros.

I never programmed PICs earlier, so I had to found out, that the PICKit alone is not enough to load the .HEX, I needed to supply external 5V to the PIC. I downloaded from here the different HEQ5.hex files, which turned out to be different than what I created with bin2hex.

I made a "test environment" on a breadboard, the PIC, the RX/TX, 5V supply and the HC. Pin 21 tells to the PIC on the HEQ5 PCB, that which PIC is DEC (GND) and which is RA (5V) With this I was able to test the PICs before soldering them on the board. The only .HEX worked was the original HEQ5.HEX uoloaded by Malcolm on 27th of May.

The test schematic is here: https://easyeda.com/Higany/synscan-esp8266 I supplied the HC from USB 5V, because it works from 5V as well, but this needs extreme caution, don't connect 12V while testing. (Pictures:  https://photos.app.goo.gl/DFYHGF5gYhKZSGPw8 )

All the parts on the PIC side of the HEQ5 PCB are glued onto the PCB, which makes the removal of the PICs difficult, the best is to cut the legs next to the package and pry them off with a prier. This will help save the delicate PCB traces.

Unfortunately I somehow fried one  PIC and all 4pcs. A3959SLBT stepper drivers. I wanted to test them without the motors connected, and while I was checked for not properly soldered legs, they got very hot and developed short circuits inside. The situation at this point semmed hopeless and it was very difficult to find out what happened, but luckily I could locate this new problem.  After replacing the faulty PIC and the stepper drivers, I connected the motors. The HC initialized OK, but the DEC motor only vibrated and missed the steps, and one of the stepper driver ICs started getting hot. I quickly turned the power off, reworked the hot IC's output pins, which solved the problem. After testing I assembled the mount and it works fine again.

Another interesting finding, which may help others to locate problems with this board: The LED on the mount is driven by the DEC PIC. So, if the LED lights, the PIC works.

I read somewhere, that this "No response both axles" of HEQ5 / EQ6 failure can happen when dew gets in the mount through the polar scope hole. That hole was uncovered on my mount as well during its last night. So, always cover that hole after using the polar scope. If the cover was lost, a standard 1,25" tube end cap is a perfect replacement, because  the hole diameter is 1,25" as well.

I added TVS diodes on the RX / TX lines and to the 12V input. And I also designed a small protection PCB to protect the mount from reverse polarity, overcurrent, overvoltage and transients, but it is not delivered yet.

 

So, thank you again guys for this topic!

 

Edited by BZd
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@BZd fantastic work! Thanks for this post, it will unfortunately be very useful to others.

I would be very interested in knowing more about your protection circuits.

That's interesting about the LED. The LED on my HEQ5 board flashes constantly while powered on - at about 1Hz, but not regular enough to be a feature. I don't think it's supposed to. Does anyone else have this behaviour?

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  • 1 month later...

HI Astro-Geek

I have been trying to solve exactly the same problem with my  Skywatcher GOTO Dobson 14"  Behaves exactly like yours (did) previous to upgrading HC only AZ motor worked, now neither Alt/AZ. motors respond.  I get same errors message when trying to update MC firmware (it fails at 100% MCU 1). I've checked all cables and connections, etc. I've been communicating with SW in UK on this.. They been very help far, and have suggested a few things... non of which has worked so  far.  I'm no electronics genius, but it seems that  Malcom was able to repair your board. by reprograming a PIC (I've no idea what that is!).  Any assistance from either of you on this would be greatly appreciated.  I would be fine, buying a new Alt MC board.... any recommendations for a source that might have one in stock?  Thanks in advance. 

Edited by Mikeshuerto
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Hi,

Can you post up some pictures of the boards to confirm what PIC they use.  In theory it should be the same as those used in AstroGeeks DOB.  If they are 16F886's the pair can be had for under £5.

I notice that your location is in Spain, which may be the only logistical issue, in that I would suggest some form of trackable delivery service is used to send me the faulty boards and for the repaired boards to be returned should you want to take a punt on having the PICs replaced in order to see if that resolves the issue.

I'll drop you a PM with some details, and we can go from there.  It's also been a while since I did these (I've slept since doing the last set of boards :) ) so will need to look at my notes, but I'm sure we can get your dob back up and running if it is the PICs that are at fault

 

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  • 3 weeks later...

Well  done Malcom.. you have your hatt trick! . My problem appears to have been solved! Both Alt and Az motors are now responsive. Long story short -  Malcom purchased and reprogramed two PICs - one for my Alt and the other for my Az MCB. He mailed them to me in Spain, and a friend (who is a circuit board engineer) installed one of them on my Alt MCB. I had suspected that it was only the Alt board that was bad (as per AstroGeeks problem).  Anyway, both Alt and Az motors are now responsive. I still need to test alignment and tracking, but will report back on that. Thank you again Malcom... you are a 'star'..  I will keep the other PIC as backup!     FYI. I figured out that I had probably blown the Alt board when I  had inadvertently plugged the 9V battery pack of a new electric focussed into the HC socket. (both are Rj11). Dumb I know, but easy to do!

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Took the scope for a ride last night. Alignment and tracking working just fine. Here's a quick snap of Jupiter using a ZWOASI224MC with 3xBarlow.  1000 of 3000 frames captured with ASCAP, then aligned, stacked and processed in Lynkeos, then color improved in LrC. Also have about 15,000 frames of Mars to work on... Later.  Bottom line, my Skywatcher 14 inch GoTo Dobson is back up and running!  Thanks again Malcom for reprograming the PIC ... and my my mate Adam. for soldiering into MCB.

 I'm still a novice at this, so any tips on improving photo are appreciated. Plan to experiment a bit with Firecapture, but the ASICAP software is very easy to use. Im a bit limited in choice of stacking software, running a Mac... and dont want to yet dish out out for PC emulation software. 

 

2020-10-23-1855_8-Jupiter.jpg

Edited by Mikeshuerto
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Wow, that's an impressive image, love the colouration.

Glad to see that the scope is functional, and only required the one PIC.  

I don't frequent the forum as often as I used to, so if any of you guys see posts from someone having similar issues get them to tag a post on the end of this one and that will notify me.  I still have four PICs left in the bag, so can repair another four boards (or a pair of HEQ5 / EQ6 boards)

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I received another PM over the weekend from a member who just purchased a second hand 250px goto dob that had dead motorboard (MC003).  I gave the member the option of a repair, but he's since decided to look at using the arduino platform as a controller, but knows that he can always fall back on having the PICs replaced on the original board should his DIY project prove problematical.  

The thing that struck me is that all these blow boards seem to be from owners with Dobsonian telescopes.  Now this may be a coincidence, or there could be an underlying trend here... who knows :)

Anyway, the 3-0 score will have to remain, looks like I may have missed the post on this one :)  If the member who PM'ed me over the weekend does go with the Arduino, please don't forget to document the project on this forum.  I'm sure it will interest quite a few members.  

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  • 3 weeks later...

Well it's been a busy morning...

The SGL member with the damaged MC003 board had a change of heart and contacted me again to see if I would still be willing to attempt to repair  his board.  Naturally I said yes as I like to try and give these old scopes another lease of life, so details were exchanged and I received the board this morning.

One thing that was pointed out by the owner was that at some point someone had tried to effect a repair by replacing a capacitor, and wasn't sure if that was the cause or not.  He purchased the old scope second hand, so it was most likely the previous owner that had done this.  We agreed that it would be better to swap out the PICs anyway to be on the safe side, and if I was able, try and effect a better repair than the one that was on the board.  Like all the repairs I've done, there was no guarantee that the boards would work, and this is compounded when there are other damaged parts rather than just blown PICs.

I carefully removed the old capacitor, and inspected the PCB.  All but one of the pads where the cap originally sat had been lifted completely.... Evidence of a sharp implement had been used as there was exposed copper on a couple of other tracks, and there was just enough of the track that attached to the Vss pin of the L293DD left to hint that this originally went to the positive leg of the capacitor.  Anyway I managed to solder insulated links to the exposed track, and install a new capacitor, and then hot glued the links in place to prevent further damage.  I can't see any other connections to the power rail at this point, but without a schematic, or decent images of an original undamaged board to compare it, I can only be 90% certain all the connections have been reinstated.

The old PICs were removed using a cutting disk on a minicraft drill.  Only two pads on one PIC lifted due to the age, and fortunately one was just an unconnected pad, and the other had enough left to be able to make a solder joint.  New programmed and verified PICs were soldered in place and the board is now awaiting shipping back to the owner for testing.  I'm hoping that the damage caused by the removal of the original capacitor didn't cause any other issues and that the repair turns out to be another success.

 

S2600002.jpg

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S2600005.JPG

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  • 3 weeks later...

Well it looks like this is one board that is just not repairable.  When the owner received the board back it still displayed the "both axis not present" message, so I persuaded him to send the board back to me and include the handset so I could test the repair.  Well this was received today and I've spent best part of the day having fun trying to resolve this boards problems.

The first thing to do was to power up the board using a Meanwell 12v PSU and see if anything was getting warm, which proved negative, so then it was out with the test meter.  I checked that 5v was getting to the two microcontrollers, which it was, so that was a good sign that the regulator was still OK.  I then spent a few moments tracing out the connections between the handset port and the two TX and RX lines, which wasn't straightforward as it would seem due to the way the two serial ports are connected to the same pins, plus the board is multi layered so sometimes a component would connect to a via that didn't connect to a trace on the top or bottom of the board which makes things difficult.

Anyway, after several hours of testing, tracing and remaining a few jumper wires I would still get the same error message on the handset.  Not having the schematic, or service manual (assuming it may exist) really meant I was just having "educated" guesses as to possible things to try.  In the end I bit the bullet and cut the old PICs off the board and removed the legs, being as careful as I could not to damage any additional pads.  Only one broke, but that was easy to add a link to after the replacement PIC had been soldered back in place.  Two new PICs were programmed with the Dobsonian firmware code, verified and then soldered back into place.  Connections were tested to make sure that each leg that had traces (I had taken photos before) made contact with the VIA or component where required, and then powered on the board and checked the voltages on each pin matched the ones I had noted down before the PICs were removed.  Pleased to say the were the same, so this would suggest that the soldering was good.  But plugging the handset in gave the same message.

I'm still going to try a few things... but my gut feeling is that whatever the previous owner did to this mount when they tried to repair it (presumably then selling it as it no longer worked) has done more damage than just blowing the original PICs.

Stay tuned....

 

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