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I have a broken linear encoder that I want to repair...

Dan Boy

Jun 12, 2015
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Hi, I allowed some coolant fluid get into my linear scale and now the read head won't work. I am guessing that the fluid, mainly water based has broken some of the components.

I hope someone can them and tell me how to test and or replace them.

003_zpspr83zilq.jpg


004_zps5ukpoe4c.jpg
 

Minder

Apr 24, 2015
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Is it optical or inductive/capacitive?
It could be cured by cleaning and drying, especially if optical.
Use de-natured alcohol on the scale.
M.
 

Dan Boy

Jun 12, 2015
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I am guessing but I think it is optical. It reads lines printed on a piece of glass. Do you mean to clean the glass or the component?

Thanks Dan.
 

Dan Boy

Jun 12, 2015
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Just gave it a clean, both the glass and the sensors. A little dirt came off but it still doesn't work. Can I test the components on the PCB?
 

Arouse1973

Adam
Dec 18, 2013
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Hi Dan Boy
Can you take some better pictures please they are a bit unclear. We can't see the extent of the damage
Thanks
Adam
 

Dan Boy

Jun 12, 2015
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Is this any better, the thing is so damn small. I can test the components if I know what reading I should be getting.

Untitled1_zpsln7usudj.png
 

Arouse1973

Adam
Dec 18, 2013
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Those three resistors look like they could do with a re-solder. One looks like its moved quite a bit. Or not centered during reflow, an indication of not enough solder or too low heat.
Adam
 

Minder

Apr 24, 2015
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Is that the read head itself? The part the moves over the scale? It does not appear to much in the way of electronics on it, if optical there should also be opto RX TX and a part of a grating similar to the head, Unless it is capacitive?
M.
 

Martaine2005

May 12, 2015
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Those three resistors look like they could do with a re-solder. One looks like its moved quite a bit.
That middle resistor definitely tried AWOL during the wave soldering.
Perhaps a good clean with isopropyl (using ear buds / qtips).
And make sure the board is completely dry.
Martin.
 

Dan Boy

Jun 12, 2015
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Before I break out the soldering iron, can I test the resistors to see if they have failed?

There are more boards to this read head but this seemed the most likely one to fail as it was in the coolant.

Thanks Dan.
 

Martaine2005

May 12, 2015
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Hi Dan, you can't really test a resistor without de-soldering a leg. To do so in circuit will give false results.
First clean all boards and let them dry COMPLETELY.
The water based fluid could still short circuit even when you think it is dry.
Heck, I should know, my computer mainboard only got 1/4 of a can of beer.
and wouldn't work for a week. I am typing to you now on it...
Coolant is corrosive and gels. Clean all boards thoroughly as smd's can retain moisture underneath too.
Martin.
 

Minder

Apr 24, 2015
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What make of scale/DRO is it?
The two small bearings at right angles indicates this is the read head, it is imperative for both type that alignment is maintained.
I don't see any optical head there, so is it possible capacitive?
I have always found that they are fairly impervious to coolant etc, that a scale/head clean could not overcome, particularly for the optical type.
M.
 

Minder

Apr 24, 2015
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You can get electronic cleaner in an aerosol can from most electronic suppliers, get the non-residue type, alternatively use de-natured alcohol.
M.
 

Minder

Apr 24, 2015
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They almost appear similar to fuseable links or contact pads?
Do they all measure the same continuity?
M.
.
 

Dan Boy

Jun 12, 2015
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I can't get any reading off them at all. On the other side there is a glass eye.
 

Minder

Apr 24, 2015
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They most certainly are the IR LED's (or could be Photo det side).
M.
 
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