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ETX-90 reverse polarity fix.

cassegrain equipment Maksutov Meade mount
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#1 Myk Rian

Myk Rian

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Posted 16 February 2020 - 06:30 PM

Connecting the power to an ETX-90, and an LX-90, in reverse, suddenly gives you a dead mount. It burns a trace on the board, as you can see.

There is a fix. It takes a very small tipped soldering iron, a little dis-assembly of the mount and RA gears.

 

I soldered a 1a fuse to a couple wires, and soldered those to JP1 pin 4, and J1 pin 1.

A cheap fix for an impossible to find board.

 

20200216_165126.jpg


Edited by Myk Rian, 16 February 2020 - 07:09 PM.

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#2 Myk Rian

Myk Rian

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Posted 16 February 2020 - 06:32 PM

A couple more pics

 

20200216_152650.jpg

 

20200216_163054.jpg

 


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#3 Piet Le Roux

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Posted 18 February 2020 - 11:04 AM

Adding a fuse is a good idea but by the time it blows a lot of damage could still have been done. Add a diode (like a 1N4001) after the fuse with its anode to negative and cathode to positive, the diode would not conduct if the polarity is correct but when it gets reversed it would conduct and blow the fuse immediately before any damage could occur.  




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