[Chiltern Hills]

Perhaps buried deep within the forum archive, but I wonder if anyone has taken apart a Pentax Motor Drive LX ?
With a successful outcome !

[Lord Lucan]

I have. What is the problem?

[Chiltern Hills]

Thanks for your reply. I have a faulty Motor Drive LX; but also have a good one with Grip LX, so able to give power to the faulty one.
No power is getting from the Grip to to MD motors (off the camera). Taken top plate off MD, and can see that it might be wise to go no further before asking for advice.
Happy to push on and get it going if possible, since I have a working MD with power from the Grip.
Is a circuit diagram available?

[Lord Lucan]

It is at least 25 years since I dismantled mine to repair a mechnical failure, so I can't remember much but I have found a few notes I made.

I removed the outer top plate like you have done. I then removed some screws from the inner top plate but that did not get me anywhere. It looks like I then peeled back some leatherette and undid a total of eight horizontally oriented countersunk screws around the periphery of the top plate and also four screws around the rear control panel. I may also have needed to remove a tiny screw in the bottom next to the tripod socket. I think I could then pull the top plate out of the rest of the body - my memory is vague but I must have solved the problem, whatever it was, because it works now. The main reason I made notes and sketches was to note the sizes and positions of the numerous screws, measuring the length and diameter of each with vernier calipers as I remove it - like some are 2.9mm long and others are 3.2mm.

I also took a look inside the battery pistol grip. Looking down at the four contacts that lead up to the camera, from behind (ie the photographer's position), the one at north-west with a red wire is 18 v (battery volts) when the selector switch is at C or S, the one at south-west with an orange wire is 18v when ditto and the trigger is pressed, the one at north-east with a green wire is at 0v when the selector is at C (otherwise it is disconnected), and the one at south-east with a black wire is at 0v when the selector is at C or S (otherwise it is disconnected).

Limited help I'm afraid, but hopefully better than nothing.

[Chiltern Hills]

Very helpful, thanks.
I aim to make a start in a day or two. You peeled back the leatherette, that's a good clue. I was hoping the top or bottom 'plastic' plates would be freed up by removal of the screws we discussed. Obviously not quite that simple.

OK: All small screws around each side close to top plate removed, these are just underneath the leatherette. Single small screw removed next to tripod mount thread. The whole of the bottom section, consisting of the entire surround and base plate slides off. (As discovered, no need to remove single screw top centre of control switch panel, this holds a small printed circuit board in place).
Inside: at least two printed circuit boards, with very fine connecting wires. Presumed pulsing circuits for motors.
1st point of weakness: Gold plated, leaf spring actuated contacts, which feed power to motor drive; these are very delicate. One leaf spring seems not making good contact with gold plated pin.
TO BE CONTINUED..!