22 replies to this topic

[Ryuno]

I accidentally confused the net adapters of the two EM11s I have and plugged the 24V power supply of the green Temma 2 Jr. into the white 12V Temma 2 M and fried it. It's now completely dead.

 

I live only 40 miles from the Takahashi factory, but their repair shop isn't cheap at all, and their retailer in Tokyo, Starbase, is closed from today until at least May 6th, because of the Corona-crisis, which has finally caught up with Japan as well. 

My questions:

 

Can I repair the fried mount myself?

Is there anyone out there who might have tried this before, be it with Takahashi or any other brand, or some other experienced DIY-astronomers who could give me some advice?

 

Thanks and clear skies from Tokyo

 

Here are the two actors in this drama, as well as some close-ups to show that it might not be so trivial to remove the cover of this box, because the motor cables run through it. I suppose you have to unplug the cables from the motors first. I once tried to loosen some of the screws that apparently are holding the box in place, but gave up rather quickly, because I had a feeling that something unfathomable was happening on the inside. Well, maybe I should just try again with a little more courage?

 

 

 

Edited by Ryuno, 09 April 2020 - 11:28 AM.

[Geo.]

https://1.bp.blogspo...00/IMG_1799.JPG

 

http://astrosurf.com...i EM-200/EM.htm

 

Look for damage in the location indicated.

 

[Phil Sherman]

I wouldn't try to fix the motor control board inside the mount because there's probably a number of fried components on it. You might be better of getting a replacement board and swapping them. If the mount hand controller was attached, you probably blew that too unless it's powered from a regulator that survived.

 

Check the web for instructions/video for getting to the board.

[Ryuno]

Thank you, George and Phil, for replying so quickly. This is the first light at the horizon. I searched the web intensely for disassembly and board removal instructions, so far to no avail. I started my career as a professional astronomer many years ago, then changed direction, and finally came back to  astrononomy, this time as an amateur, but I have never dealt with the inside of the gear I have been using.

 

The people at Starbase told me there were no fuses.

 

I was hoping I could open the box and look at the boards inside, and maybe see some damage, or check some of the components with a multimeter to find blown resistors. Being a physicist, I know how to do that, but that's about all I probably could try. I might even be able to replace defective resistors. I have good soldering gear, and on the web there are a large number of videos explaining how to solder on boards.

 

 

The other option is to wait for Starbase to reopen, but that can take months, nobody really knows. And in these Corona-times it is wise to avoid expenses if possible. I've got time now and would like to try a few things myself.

Warranty has ended, nothing to lose there, but of course i want to avoid doing any further damage to the mount.

 

I hadn't thought of the possibility of having damaged the hand controller too. Thank you, Phil, for  pointing that out.

Edited by Ryuno, 09 April 2020 - 05:41 PM.

[SonnyE]

I'd recommend you return it for servicing at the factory. Explain what you did. Pay the bill.

Then you'll have it back in 100% working order.

 

And put an unmistakable flag on the 24 volt power supply so you never do that again.

I would change the connector so it cannot be poked in the wrong hole again.

[Ryuno]

Well, SonnyE, the story might end as you are suggesting, thanks for the advice.

In the meantime I opened the hand controller. If there is any damage on this board, I don't think I could ever fix it and have to wait until Starbase reopens, or pay a visit to the factory itself. But of course I have no idea if they are open. And if they are, would they receive me at all?

[orlyandico]

The Temma electronics is antiquated. If you can get the parts, it should be possible to retrofit with OnStep

 

http://www.stellarjo...quipment_onstep

 

using the existing motors and for under $100.

[Phil Sherman]

The most sensitive component in your hand controller is an IC. Overvoltage will instantly blow these. The same applies to the board in the mount. The most common device to fail on an overvoltage is a capacitor. The boards may have 15 or 20v capacitors which will blow with 24v applied to them. A capacitor is usually one of the first components to get power on the board.

 

Most ICs are 5V devices. If true for the board, then 12V in feeds a regulator. Most of these will take 30V without failing. It's also possible that the board contains an overvoltage crowbar circuit that blew a fuse and saved the rest of the circuitry. A schematic would show this.

Edited by Phil Sherman, 10 April 2020 - 01:24 PM.

[Ryuno]

Orlyandico, the Onstep looks very interesting. I'll have closer look at it. Thank you for pointing it out.

 

Phil, as I wasn't able to find disassembly instructions for the EM11 online, I made one more attempt to open the box. And gave up again, because the only result is  a loose washer or something moving freely around inside the box. There has to be some secret way how to disassmble it. Without detailed instructions I believe it's impossible. Remains SonnyE's proposal. I'll take it.

Edited by Ryuno, 10 April 2020 - 05:30 PM.

[SteveGR]

Thank you, George and Phil, for replying so quickly. This is the first light at the horizon. I searched the web intensely for disassembly and board removal instructions, so far to no avail. I started my career as a professional astronomer many years ago, then changed direction, and finally came back to astrononomy, this time as an amateur, but I have never dealt with the inside of the gear I have been using.

The people at Starbase told me there were no fuses.

I was hoping I could open the box and look at the boards inside, and maybe see some damage, or check some of the components with a multimeter to find blown resistors. Being a physicist, I know how to do that, but that's about all I probably could try. I might even be able to replace defective resistors. I have good soldering gear, and on the web there are a large number of videos explaining how to solder on boards.


The other option is to wait for Starbase to reopen, but that can take months, nobody really knows. And in these Corona-times it is wise to avoid expenses if possible. I've got time now and would like to try a few things myself.
Warranty has ended, nothing to lose there, but of course i want to avoid doing any further damage to the mount.

I hadn't thought of the possibility of having damaged the hand controller too. Thank you, Phil, for pointing that out.

Fuses would not have helped, I'm afraid, fuses prevent fires, they don't really protect any electronics. If a component is going to fry, it will do so faster than even a quick acting fuse will.

[MCinAZ]

  From the liability perspective, it would be a bit unusual if there weren't a fuse or some kind of protection device. An internal short of a device potentially connected to a 12 V automotive battery with no current limiting element is a fire hazard. Perhaps there is some type of protection device such as a conventional or poly fuse soldered to the board, so not considered user serviceable, thus the information from Starbase.

 

  If there is a protection device, it may well have opened, though not necessarily before other components failed. A capacitor failure by itself wouldn't necessarily lead to a dead unit since it's a DC circuit. Also, catastrophic capacitor failures are usually accompanied by smoke, a loud pop, or both. Most voltage regulators can withstand 24 V, however the power dissipation limit could easily be exceeded, leading to internal failure. That may result in a charred package, but that isn't always the case.

 

  It's very difficult to estimate the extent of damage likely in a sustained overvoltage situation, especially without access to a circuit schematic. If the only component exposed was a linear voltage regulator, damage may have been limited to it. Or it's possible that the regulator withstood the overload condition long enough that a protection device opened (as voltage increases, so does current draw, which is what triggers such elements), and everything downstream is still good. But cascade failures are possible, in which case many other components could be damaged.

 

  Since the mount is out of warranty, you're probably not out a lot if you want to attempt repair. So long as you don't physically damage anything in your attempts to disassemble the controller from its housing, board repair costs shouldn't be affected. If you do succeed in removing the circuit board, good quality photos of the front and back may provide some useful hints in assessing potential damage. It would also be easier to spot a protection device.

 

  As a simple preliminary test, I would measure the resistance between the two 12V power leads. If you see an open circuit, that may be an indication that there is an internal protection device which has opened. If you measure resistance, things are still connected internally, but obviously something is not right.

 

  When the unit was connected to the 24 V supply, was there any smoke, popping or crackling noises coming from the controller, or did you smell burning insulation? How long was 24 power applied to the unit?

[SonnyE]

Well, SonnyE, the story might end as you are suggesting, thanks for the advice.

In the meantime I opened the hand controller. If there is any damage on this board, I don't think I could ever fix it and have to wait until Starbase reopens, or pay a visit to the factory itself. But of course I have no idea if they are open. And if they are, would they receive me at all?

I think the professional help is the best route in these cases.

 

Welcome to the Human Race! You aren't the first, and surely won't be the last to accidentally connect wrong.

It is very fortunate you are so close to the source.

 

They might have a complete tune up package to go with the repair.

Imagine getting back a better than new mount to enjoy for decades ahead. 

[Ryuno]

MCinAZ,

let me answer your questions first: 

 

1. When the unit was connected to the 24 V supply, was there any smoke, popping or crackling noises coming from the controller, or did you smell burning insulation? 

I have to answer "No" to all of these questions. My friend, who was with me via Skype, confirms this fact. The mount just stopped working quietly without further ado.

 

2. How long was 24V power applied to the unit?
Just for a very short moment. My friend even insists that the mount stopped working after 10-20 seconds. I don't know if it was that short, but short it was.

 

Your message provided the courage and the knowledge to make me try one last time to access the interior of the EM11, at last with success. It was in the end easier than expected.. Here are some photos. I connected a 12V power supply and tested the voltage between the two points indicated by arrows. The voltage was 0V.  If these two point were the correct ones to measure, I suspect that the 12V-in-port was fried by the 24V power supply and needs to be replaced. If I am lucky, this solves the problem. I tested the 12V power supply I used, before I started. It was working as advertised and I measured 12 V within the stick. 

In case you need a higher resolution, you can find them in my galler/y

 

What do you think? Is my reasoning correct? And if yes, do you believe that after some practicing I would be able to exchange the defective power-port myself? What else would you recommend to check at this moment?

 

Thank you very much for your explanations and concern so far.

 

 

[Ryuno]

I think the professional help is the best route in these cases.

 

Welcome to the Human Race! You aren't the first, and surely won't be the last to accidentally connect wrong.

It is very fortunate you are so close to the source.

 

They might have a complete tune up package to go with the repair.

Imagine getting back a better than new mount to enjoy for decades ahead. 

SonnyE, If my attempt to repair the mount myself fails, I will have to send it to Takahashi for repair, I suppose.

With regard to a possible upgrade in connection with a repair, as far as I know, Takahashi have no record in this respect, but it would of course be a nice surprise.

[Live_Steam_Mad]

OK I think I might have an answer for my friend in Japan ;- have a look at that picture of the EM11 main PCB that you posted here in your Gallery. Locate component "EX1-2U1S" right next to the 12V socket in your picture, the one made by NEC / TOKIN, the big white thing. EX1-2U1S is a 12V relay. The coil is rated for 12V, I imagine that you have burnt the relay out by giving it 24V, that's maybe why we didn't smell anything. Replacement looks like this ;- https://www.amazon.c...J/dp/B079HWSCJD

 

It's 5 solder joints onto the PCB holding the relay in place. Desoldering is possible, but tricky. You will need a 50W iron and a large tip, I happen to have one, an Antex TCS iron with 4.7mm chisel bit (angled, oval, single face bit). The third picture down in that Amazon link above shows the 5 legs that the relay has that holds the relay onto the PCB and the legs will be soldered onto the PCB. It's a fairly straight forward task to desolder the relay to get it off the PCB, but I don't know if it is possible that in the time it took for the relay to burn out that other components in the chain later on might have been damaged also but let's hope not.

 

Here is an example listing on Ebay UK for a replacement relay ;- https://www.ebay.co....VcAAOSwqpBdVAXv . Googling for "overvoltage protection relay" shows that using a relay as an overvoltage protection device is apparently reasonably common throughout industry for circuit over voltage protection. Seems that Takahashi were expecting some people to make this mistake of plugging 24V in from people who previously owned the old mount or had both old and new mounts and it appears that Tak have already thought of it before...  I imagine that the Tak factory has been asked to repair a few of these over the years and have seen this all before. I wonder what the factory would charge for the repair?

 

Best Regards,

AG

Edited by Live_Steam_Mad, 14 April 2020 - 08:58 AM.

[PaulE54]

If it is the relay coil that has gone, it will be open circuit, hopefully could confirm with a multimeter before bothering to unsolder? If the relay coil is still measuring as if it is intact, need to look elsewhere. Crossed fingers....

 

Paul

[Ryuno]

AG and Paul, thanks a lot for your replies. I am not so firm in electronics. What is an open circuit and how can I check if this is indeed an open circuit, and if the relay is fried or not?

[Michael Covington]

Open circuit means no current flow (no connection).  Test with an ohmmeter.

 

I have no experience with this particular circuit, but I can tell you that commonly, when excessive voltage is applied to a piece of equipment, the damage is confined to one or two components very close to the power input.

[Iver]

Hi, if it turns out you need to send it in for repair there is this option. Someone already mentioned the OnStep project, but if you are not comfortable building one you can get one already built here.

 

http://instein.eu/onstep.htm

 

If my Temma 2 Jr. fails I plan to convert to this!

[Phil Sherman]

If you lack the electronics skills to further diagnose the problem, you might try locating an amateur radio club near you. They should have a number of members familiar with electronics testing and working on printed circuit boards. Another possible location to get assistance is a school with an electronics program.

[Ryuno]

Problem solved by intercontinental cooperation!
My friend in England and I fixed the mount together. I pass the word on to him, to give you a short report, because it was mostly due to his expertise, we succeeded.

[Live_Steam_Mad]

As an update for you all, I have been helping with my friend in Japan, and between us we worked out how to fix the mount, both temporarily and permanently. As I suspected, the culprit was indeed the 12V relay, and first we tested the coil between pins 2 and 3 (see datasheet ;- https://www.mouser.c...2_e-844962.pdf

...and suprisingly there was still a resistance measured, about 600 Ohms if I remember correctly, but when power was applied at the 12V socket, the relay didn't ever go click with an audible click, we checked. To make the mount work without the relay, we jumped it by connecting pin 1 and 4 (using a multimeter without a suitable wire at hand) , because when the relay is off the connection is between pins 1 and 5, and when the relay is on, the connection is between pins 1 and 4. Bingo!, the mount's LED light on the main PCB lit up and it seems that we had carried power to the rest of the circuit, and bypassed the relay. Hopefully the rest of the components were protected by the relay... well we can only hope.

So... to fix this temporarily all that has to be done is to connect up pins 1 and 4 on the relay with a thin wire insulated except for at both ends, soldered onto the relay at pins 1 and 4. However this would not be a good idea in the long term in case 24V is fed into it again, because this time the rest of the components would go pop! So the best course of action is to replace the relay. The relays are about 20p from AliExpress (if we can get hold of one at present) But at least we now have some (!) life back in the mount and maybe all is not lost.

 

Best Regards,

AG

[Ryuno]

On this image, the relay ist the whitish box up at the centre. Below it on the underside of the board I have marked the five "feet" (pins) of the relay 1-5, as mentioned in AG's text in accordance with the drawing EX1 on page 2 of the data-sheet linked to above.

 

 

Thank you very much to all of you for your contribution to solving this. By repairing the mount myself I saved a LOT of repair cost at the Takahashi factory, of which I still don't know if it is up and running or closed down because of Corona. And I learned a geat deal about the electronics of my mount. In the end it was all far easier than I had feared.

 

All the best in these Corona-times. Take it as easy as you can, just like the Italians in this video-clip.

Edited by Ryuno, 18 April 2020 - 05:34 AM.