Etx125 Dec motor board
Posted 15 May 2021 - 01:05 AM
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.
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).
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.
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.
Posted 15 May 2021 - 05:50 PM
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.
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.