Chromatography Forum

We have three older Shimadzu LC-10AS in pieces and I took the motor out of one that had a cracked piston plate and put it into another one that had a motor error(the motor did not turn on). When I turn it on it makes 2 or 3 revolutions and then a pump pos error comes on...the manual says this is due to the motor slipping or that it can't find the home position. I cleaned all the dirt out, oiled the cam, and cleaned the sensor and wheel with IPA but no luck..I took the sensor out and the wheel and tried the other two and no luck..I also tried moving the wheel from left to right a little to get it in the middle of the sensor but that didnt help...I took the pump head off and it does the same thing...it seems to do it when the piston is fully withdrawn , i.e. when the spring is fuly extended...I'm not getting any pressure either in those few seconds nothing but the piston seal seems ok and I primed the pump and am getting solvent out witha syringe...called shimazdu and they said oil, and replace wheel or sensor..it seems unlikely that all 3 sensors and wheels are bad?
any help would be appreciated!

This may sound silly - but did you put the cover back on? Sometimes the sensor won't work if there is too much light shining on it.

HA! Yes we did try that and still no luck! Thanks that woulda been real funny if that was it!

It is interesting that you are losing pressure at that one point in time. Is there a spacer that goes behind the plunger that is missing?? - usually you will have leaking though too, or your check valves could be bad. I haven't touched a 6 series pump in 10 years... They did seem to run forever though! - good luck!

thanks for the feedback..I'm sorry what I meant to say was that I was not getting any pressure after turning the pump on and before the motor error came on-in those few seconds maybe 10 or 20 the pressure was still at 0..I just tried turning the flow rate from 0.1 to 1 to 2 to 5 ml/min and the motor did turn faster from 0.1 to 1 but from 1 to 2 to 5 it stayed about the same which is not a good sign..maybe the motor is just about shot? The head and check valves I pulled from a pump that was working and dont see any leaks or piston scores.. I havent pulled the piston out though so maybe its worth checking to see if something is missing per your suggestion...I figured with the head off but the piston still in there would be less resistance on the motor and that it might work but it gives the same result...thanks for the suggestion and I'll pull the piston to see if there is something missing...

I just pulled the piston out and there is no backing plate behind it and it looks fine....I pulled the other two pumps apart and they look the same...still not getting any pressure and still getting the same error! wish I had another working motor to try...

Is the problem sorted out? if not the following may be helpful:

1) The sensors can be easily checked with you multimuter in diode mode (google on testing stepper motors with LED and interuptor sensors to test)
2) The cam is connected with the motor and while it rotates, a bearing in the front called "cam follower bearing" rotates to move the plunger. If the bearing does not rotate freely then the cam has to put more effort to rotate because of which the stepper motor slips hence the error. 3) You can press cam follower a bit hard to the front, allowing the motor to rotate freely to confirm they run without errors.
Best wishes to solve the problem.