Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Etx125 Dec motor board

  • Please log in to reply
6 replies to this topic

#1 JerryCronus

JerryCronus

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 07 May 2021

Posted 15 May 2021 - 01:05 AM

Hello,

A while back the declination motor board on my etx125 let out the magic smoke. I've been looking for a replacement for a few months now. Does anyone know where I can source one? I have an etx125pe with lnt.

Thanks

#2 CltFlyboy

CltFlyboy

    Apollo

  • *****
  • Moderators
  • Posts: 1,025
  • Joined: 06 Dec 2019
  • Loc: Charlotte, NC

Posted 15 May 2021 - 08:30 AM

Jerry - Welcome to Cloudy Nights! You might want to post this to the classifieds once you have been on the forums for 30 days (new users can't post to classified until then). There are a LOT of people here, someone may just have what you're looking for (and your want ad will get a lot of visibility).

 

Cheers!



#3 kg74

kg74

    Explorer 1

  • *****
  • Posts: 66
  • Joined: 28 Feb 2021

Posted 15 May 2021 - 11:49 AM

Have you tried the repair route?  First - what caused it to get smoked?  Depending on cause you may need other components other than the board itself.  I am not familiar with the scope, but there are diagrams out there so some level of repair is feasible. 

 

Can you post some pictures of the front and the back of the board?  Do you have a VOM?

 

It could be a voltage regulator and a few other minor items in the power circuit. 



#4 JerryCronus

JerryCronus

    Lift Off

  • -----
  • topic starter
  • Posts: 2
  • Joined: 07 May 2021

Posted 15 May 2021 - 12:05 PM

As a matter of fact I do! I think you mean a volt meter correct? Yes I have one.

Here the front and back of the board in question. You can see a burned trace. One of the chips is burned on the front as well.

http://imgur.com/a/QD4tcrv

#5 kg74

kg74

    Explorer 1

  • *****
  • Posts: 66
  • Joined: 28 Feb 2021

Posted 15 May 2021 - 02:22 PM

What are the printed numbers on Q1 and Q2?  I don't know much, but with the numbers I can pull up the data sheet and that will tell what are the chips' function.

 

Regarding the burned trace - what is the polarity of the pins on JP1 (you should see the plug in wire being red and black is my guess).  In inside pin of JP1 has distorted plastic - is that removal wounds or melt?

 

Before it smoked was anything changed or did it just fail?  Does the other motor work?  Thought being maybe something upstream failed.

 

It looks like every IC on that board except for U1 can be swapped out. U1 is a Pic16 which should have the firmware on it.  I am new to Meade electronics, but from what I have read their Pic chips are locked down. 



#6 OzAndrewJ

OzAndrewJ

    Aurora

  • *****
  • Posts: 4,849
  • Joined: 30 Nov 2010

Posted 15 May 2021 - 05:50 PM

Gday Jerry

 

That burned trace looks like it is going to the jumper pin,

ie it is the power to one side of the motor

 

Q1 and Q2 are dual mosfets that form a HBridge supply for the motor.

It is uncomfortably common that the PCh mosfet burns out on these

and simply replacing them fixes it, as long as they didnt explode and take out the

traces on the chip side of the board.

Q1 should be marked 4936 and is the NCh mosfet

Q2 should be marked 4947 and is the PCh mosfet ( the one that normally dies )

 

It might pay to test the motor using an external power supply to ensure it isnt faulty

as the burnt trace doesnt normally happen, so maybe the motor drew too much current

vs the mosfet died just by itself

 

If you just use the forum search utility and look for "Mosfet"

you will get lots of threads on this problem.

 

Andrew Johansen



#7 Geo.

Geo.

    Vendor - Nexstar Parts

  • *****
  • Vendors
  • Posts: 5,638
  • Joined: 01 Oct 2008
  • Loc: Upstate NY

Posted 21 May 2021 - 07:19 PM

The PE has a somewhat unique board as the cabling for the north/level sensors ran through it. Otherwise any DS or ETX Alt board will work. 




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics