Uggh … a Hail Mary, use the soldering iron to re-flow (heat till solder flows) the connections on the sensor.
In fact lets reflow all the connections and look very closely to see if any traces are broke or cracked.
Noodling what we can try next … were do you live?
I am in Lyman South Carolina. I just made an observation. On the side of the sensor with the anode and cathode there is what appears to be a small clear hemisphere. Like looking at the end of a led. On the side of the sensor with the emitter and collector there is not. Should not be sides have this lens structure? Maybe the plate damaged the lens on that side?
this pict shows two hemispheres.
https://plus.google.com/u/0/photos/113684285877323403487/albums/6334748949069611569/6334748951563130690
You may be right the only way to know is to power the board and look for a signal when you interrupt the sensor.
you can get a new one here: http://www.digikey.com/product-detail/en/vishay-semiconductor-opto-division/TCST1030/TCST1030-ND/2354846?WT.srch=1&gclid=CjwKEAjwjqO_BRDribyJpc_mzHgSJABdnsFWxtL51Xs-gQTcy02na9Bb_jUemKen7F1KwS0BHcrk_xoC-ebw_wcB
I have ordered a new sensor from a local electronics supplier. It was not in stock so I have to wait a few days. In the mean time, I have been in contact with the eBay seller. They instructed me to have it repaired by a local technician and they would pay the repair bill. How do you find someone local to work on a Chinese laser??
Video of the malfunction
If I was closer, I’d do it for ya 
I want to look for a local person to help me with this’
What technical training or occupation should I look for?
electronics technician or electrical engineer. I am willing to help advise anyone you select.
Just wondering Don, If you have viewed the video I posted showing the machines malfunction? After viewing it, what would be your first course of action to troubleshoot the problem?
I would measure the output of the sensor at the Nano end of the white cable while power is on and putting a piece of paper in-out of the Y endstop sensor. It should go from 0v to 5v.
It seems to me that it would be natural for the carriage to move in the wrong direction if the endstop sensor were stuck on. The carriage thinks it is already in the home position, so it moves away from home waiting for the switch to disengage until it reaches some internal maximum distance determined by the software and gives up. If so, this should be easy to test. Disconnect the sensor and wire up a switch with a pullup or pulldown resistor for testing. I don’t know offhand if the endstop is supposed to be active high or low, so try both ways.
@Vince_Lee the endstop is high when interrupted.
Don, referencing your daughter card schematic of the sensor, am I correct that the test points for this would be the Y home lead and ground?
@timb12957 I have to do an errand I will give you a picture when I return in about an hr. You really want to check it at the Nano end of the cable to insure that it is getting all the way through …
If those are the correct points to test, under power I get 2.5v with sensor open, and when interrupted it goes to 4v
Very good, and yes I was testing on the Nano connector
@timb12957 the fact that it changes suggests that you are on the right pin.
4V might be ok but seems low, however when not interrupted Y should be closer to gnd as the photo transistor in the sensor should be turned on.
2.5V is marginal for digital logic to see the sensor as NOT interrupted.
My guess is that the Nano sees this as an interruption or like the sensor is always at home.
Thinking of what could cause this:
What does the power supply read on the controller board?
-Improper current in the transmitting LED side of the sensor.
Look for:
Bad 5V on the daughter card.
Bad 5V on the resistor that goes to the LED side of the sensor.
Bad resistor on LED side…
For reference: Here is a portion of my machines schematic (only the connector and its signals apply to you) the dot is the signal you are testing. Also measure the 5V on that connector that goes back to the daughter.
Resistor checks good. Input voltage to daughter card and at resistor is 3.87v
@timb12957 that seems to low I expected it to be 5V or whatever the LPS puts out. What is the 5V on the nano and the LPS connector measure?