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CG-4 Hand Controller-Have I burned it?

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#1 alibinreceb

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Posted 26 February 2021 - 03:47 PM

Hi. I applied 7.5v to my cg-4 mount motor drive (stupid me). Now when I give it 6 volts the LED on the hand controller is constantly red/orange and there is no movement in motors no matter what I do. If anyone has burned theirs before, is this how it behaves when it gets burned because of high voltage? And also is there a way to fix this by maybe replacing some of the damaged components or is it hopeless? Thank you.



#2 emflocater

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Posted 26 February 2021 - 04:00 PM

Curious...how in the name of the Lord did you apply 7.5v to mount? Sound like you may have fried the main board if it has one like the CG5 or fried the Motor or fried the Hand Controller or 2 of the 3 or all 3. 

 

Cheers

Don



#3 alibinreceb

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Posted 26 February 2021 - 04:18 PM

Curious...how in the name of the Lord did you apply 7.5v to mount? Sound like you may have fried the main board if it has one like the CG5 or fried the Motor or fried the Hand Controller or 2 of the 3 or all 3. 

 

Cheers

Don

I used to use a 6v dc adapter to power the mount. It has adjustable voltage and one of the options is 7.5v. That is how I applied 7.5

Right now the only thing that gives me little hope is that red LED



#4 Celerondon

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Posted 26 February 2021 - 10:25 PM

You may have let the smoke out of something. frown.gif

 

What normally happens with your controller LED?  Does it flicker during drive operation or is it perhaps a constant but different color? 

 

The good news is that your problem can definitely be repaired.  Some solutions require pre repair diagnosis and others merely require cash.      smiley-char145.gif  /  moneyeyes.gif

 

Good luck!

Don 


Edited by Celerondon, 26 February 2021 - 10:34 PM.


#5 DAVIDG

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Posted 26 February 2021 - 10:30 PM

 I bought a dead one and repaired it a couple of  years ago  so it has been awhile and I'm going from memory. What I found is that the circuit used a "brown out" IC that if the voltage is  below a certain value it  would  shut down the microcontroller. So if that IC was damaged it is holding the enable line on the microcontroller in  a state that is stopping it from turning on. I believe it also supplied a reference voltage that went to  an OP amp setup as  a comparator which controlled the color of the LED. So if the reference voltage isn't there it could also cause the LED to stay red.

 

             - Dave 


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#6 alibinreceb

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Posted 27 February 2021 - 04:26 AM

You may have let the smoke out of something. frown.gif

 

What normally happens with your controller LED?  Does it flicker during drive operation or is it perhaps a constant but different color? 

 

The good news is that your problem can definitely be repaired.  Some solutions require pre repair diagnosis and others merely require cash.      smiley-char145.gif  /  moneyeyes.gif

 

Good luck!

Don 

Normally the LED is green until one of the buttons on the hand controller, while they are pressed it goes red, then when the button is released it goes green again. And also normally, it is constantly red when the voltage is low. (Which I don't think is the case with my controller) Thanks Don. 



#7 alibinreceb

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Posted 27 February 2021 - 04:53 AM

I bought a dead one and repaired it a couple of  years ago  so it has been awhile and I'm going from memory. What I found is that the circuit used a "brown out" IC that if the voltage is  below a certain value it  would  shut down the microcontroller. So if that IC was damaged it is holding the enable line on the microcontroller in  a state that is stopping it from turning on. I believe it also supplied a reference voltage that went to  an OP amp setup as  a comparator which controlled the color of the LED. So if the reference voltage isn't there it could also cause the LED to stay red.
 
             - Dave

Thank you very much for your answer. I am not very good with electronics so I will have a few questions. Firstly I want to send some photos to identify these IC and OP amp you are talking about.

 

 

HC lid off

This is what the hand controller looks with the lid off. (I have added an ST4 port (grey piece on the right top side) manually but I don't think that has anything to do with the problem because it used to work just fine with it)

 

OP amp

I am guessing that this is the OP amp? It is written ''7AW0V7EF3    LM393P'' on it.

 

microcontroller

And is this the IC? This one says: ''STC 89LE52RC    40I-PDIP40    1426HBN535C90C''

 

 

So which of these should I try replacing?


Edited by alibinreceb, 27 February 2021 - 01:00 PM.


#8 DAVIDG

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Posted 27 February 2021 - 11:22 AM

 The LM393 is  the OP amp and I don't think that is bad. The  40I-PDIP40 is the microcontroller that is custom programmed so if it is damaged you won't be able to get one that is programmed. It has a  operating voltage that is  between 3.3 to 5.5 so it might have been damaged by the higher voltage. 

   The "brown out" device I believe is located under the black 22uf capacitor located next to the slide switch on the lower right of your picture that shows the  microcontroller. I'm going from memory from a few years ago but I think it is 3 pin device. I remember that I could get it with a number of different brown out  voltages that ranged from around 2 volts to around 5 volts.  I got mine off of Ebay and I had to be careful to get one that the highest brown out voltage since they were listed with the part number but some without the brown out voltage.

   If I'm right  you should be able to trace a line going from the brown out device to a Reset pin or enable pin on the microcontroller. Here is link to the data sheet for the microcontroller.  It looks like either pin 9  or pin 31 might be used http://www.stcmicro....C89C51RC-en.pdf

  I thought I trouble shot mine be  by pulling that line to the  correct  state that microcontroller wanted  to run and saw the waveforms being generated that would  pulse the motor.

 

            - Dave  


Edited by DAVIDG, 27 February 2021 - 12:17 PM.

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#9 alibinreceb

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Posted 27 February 2021 - 01:11 PM

The LM393 is  the OP amp and I don't think that is bad. The  40I-PDIP40 is the microcontroller that is custom programmed so if it is damaged you won't be able to get one that is programmed. It has a  operating voltage that is  between 3.3 to 5.5 so it might have been damaged by the higher voltage. 
   The "brown out" device I believe is located under the black 22uf capacitor located next to the slide switch on the lower right of your picture that shows the  microcontroller. I'm going from memory from a few years ago but I think it is 3 pin device. I remember that I could get it with a number of different brown out  voltages that ranged from around 2 volts to around 5 volts.  I got mine off of Ebay and I had to be careful to get one that the highest brown out voltage since they were listed with the part number but some without the brown out voltage.
   If I'm right  you should be able to trace a line going from the brown out device to a Reset pin or enable pin on the microcontroller. Here is link to the data sheet for the microcontroller.  It looks like either pin 9  or pin 31 might be used http://www.stcmicro....C89C51RC-en.pdf
  I thought I trouble shot mine be  by pulling that line to the  correct  state that microcontroller wanted  to run and saw the waveforms being generated that would  pulse the motor.
 
            - Dave

 
 
brown out device

 
This should be the ''brown out'' device (it has 3 pins as you said)
 
STC microcontroller reset pin:9

In the datasheet you sent I've found this. It shows pin 9 as the RST pin which I guess is ''reset''
 

connection line bottom

This line goes from where the brown out device is to the 9th pin of the microcontroller. 
 
connecting point top

And I believe this is where the connection point is (seen from top).

Please correct me if I am wrong with these

 

 

  I thought I trouble shot mine be  by pulling that line to the  correct  state that microcontroller wanted  to run and saw the waveforms being generated that would  pulse the motor.

After you replaced the brown out device with the new one you got off ebay, did it work right away with 6v?


Edited by alibinreceb, 27 February 2021 - 03:16 PM.


#10 alibinreceb

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Posted 27 February 2021 - 04:01 PM

I've just found the datasheet for this brown out device called IMP810:

http://pdf.datasheet...5/255222_DS.pdf

 

It says IMP810 on the board and it is written ALAA on the device itself:

IMP810 close Up

 

Looking at this table from the datasheet that shows different kinds of these devices (as far  as I understand the difference is the brown out voltage as you mentioned) I am confused which of these two models I should get, IMP810LEUR-T or IMP810REUR-T:

IMP810 kinds table

 

The package marking is ''ALXX'' on the REUR one (the one inside the controller is ALAA as seen in the photo above) but the voltage is higher on the LEUR one.

 

BTW I am very thankful for the useful information you have given, I couldn't have come this far without your help.


Edited by alibinreceb, 27 February 2021 - 04:46 PM.


#11 DAVIDG

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Posted 27 February 2021 - 05:20 PM

 It has been awhile but I remember some confusion on the part number vs the voltage required. I thought I found another data sheet that cleared up the markings on the original device and the voltage needed I do remember buying the wrong voltage since the seller on Ebay didn't list the  brown out voltage and I had to but a different part.  I 'm pretty sure I used one with a brown out voltage around 5 volts since the controller is run off of  6 volts Yes the unit work perfectly once I replaced that part BUT my trouble shooting determine that it was that part that was defective. 

   Pin 9 is the Reset pin and the data sheet states if it is high that causes the microcontroller to reset itself. So PIN 9 should normally be low. So what I most likely did was carefully take the microcontroller out of it's  socket, then carefully bend pin 9 outward so when the IC was placed back in the socket, that pin did not go into the socket. That would force it to be low all the time and the microcontroller should start up. I would have used an oscilloscope on one of the lines that drive the stepper motor and saw pulses on that line indicating that the microcontroller was alive. 

   Happy to help.  

 

                    - Dave 


Edited by DAVIDG, 27 February 2021 - 07:32 PM.


#12 DAVIDG

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Posted 27 February 2021 - 08:25 PM

 The reason why the  version of IMP810 is the ALAA  version  which turns on at 2.63 volts is that the voltage going to it has been reduced to say 1/2 of the input voltage ie 3 volts. I would measure the voltage going to the IMP810 and see what that value is. 

 

                   - Dave 



#13 alibinreceb

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Posted 28 February 2021 - 05:25 AM


Pin 9 is the Reset pin and the data sheet states if it is high that causes the microcontroller to reset itself. So PIN 9 should normally be low. So what I most likely did was carefully take the microcontroller out of it's socket, then carefully bend pin 9 outward so when the IC was placed back in the socket, that pin did not go into the socket. That would force it to be low all the time and the microcontroller should start up. I would have used an oscilloscope on one of the lines that drive the stepper motor and saw pulses on that line indicating that the microcontroller was alive.

I don't have an oscillator but still I wanted to give it a try, so I bended pin 9:
Pin 9 bended


Then I applied 6v again but the LED was still red. You said that the LED colour was controlled by the OP amp, so this should be normal BUT I've also plugged in the motors and they didn't move at all:

Red Led


Is it normal for the motors not to work? Or does it show that the microcontroller is dead?


It has been awhile but I remember some confusion on the part number vs the voltage required. I thought I found another data sheet that cleared up the markings on the original device and the voltage needed I do remember buying the wrong voltage since the seller on Ebay didn't list the brown out voltage and I had to but a different part. I 'm pretty sure I used one with a brown out voltage around 5 volts since the controller is run off of 6 volts Yes the unit work perfectly once I replaced that part BUT my trouble shooting determine that it was that part that was defective.

The reason why the version of IMP810 is the ALAA version which turns on at 2.63 volts is that the voltage going to it has been reduced to say 1/2 of the input voltage ie 3 volts. I would measure the voltage going to the IMP810 and see what that value is.

I couldn't find any other data sheet. So you are saying that the one I should get is ALXX version or maybe I should get both and try them? I couldn't find a seller who sells this part in my country. But I've found a Chinese dealer who sells both and ships to where I live.

Edited by alibinreceb, 28 February 2021 - 08:49 AM.


#14 DAVIDG

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Posted 28 February 2021 - 09:51 AM

 I think your microcontroller might be dead. I would try pulling pin 9 to ground to make sure the controller is not in reset mode. So with  pin 9 still not in the socket run a wire from it to some place that is ground on the circuit and see if the motors start to work. 

 

                   - Dave



#15 alibinreceb

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Posted 28 February 2021 - 11:01 AM

 I think your microcontroller might be dead. I would try pulling pin 9 to ground to make sure the controller is not in reset mode. So with  pin 9 still not in the socket run a wire from it to some place that is ground on the circuit and see if the motors start to work. 

 

                   - Dave

Yeah it is dead :/

I've tried it with pin 31 too, it is definitely dead undecided.gif

 

But at least we have created some content for those who might face the same problem in the future. I wasn't able to find anything on this issue on the internet. Hopefully others will be able to fix theirs. Thank you again Dave for your help and time


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#16 Terra Nova

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Posted 28 February 2021 - 05:49 PM

Using a 12V lithium rechargeable power supply and a plugged in 12V > 6V portable power supply to run these drives is definitely a tantalizing prospect and I have indeed done just that, but it’s taking a road that’s fraught with dangerous curves, can potentially lead to your particular predicament. Even tho I’ve been successful, with the cost of these drive systems increasing, I find myself more and more reluctant to do it, and fall back on the old tried and tested array of four D-cells. After all, their cheap, they work, and they work a long time. For those contemplating going the experimental route, you might want to read this thread:

 

https://www.cloudyni...o-6v-converter/

 

By the way, the Celestron CG-4 dual drive system is identical to the Orion EQ-3M system, and Orion offers both dual drive and single (RA) drive systems. Since yours may now in-fact be dead, you can save yourself both money and battery-life by replacing it with the Orion EQ-3 single axis drive system, (now $99.99, it used to be $69.99):

 

https://www.telescop...rive/p/7829.uts

 

That’s what I’m using on my CG-4 and it works quite well. Just put your manual Dec control knob back on and use it. After all, a Dec slow motion is needed far less anyway, and slewing with it eats your batteries. 


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