MD-15 motor drive for FA - shorted when batteries are put in

Hi,

I just got a nice MD-15 motor drive for my Nikon FAs, and I got it cheap. When I insert the battery bay, it gets hot so I assume it's a short. When I measure between the poles inside the battery compartment there is no short but high resistance. I'm not an expert but I'm now hoping that someone has a clue for me to start finding a solution.

I can solder and fix general things that are reasonably complicated, but I can't see what this might be

tilder said:

Hi,

I just got a nice MD-15 motor drive for my Nikon FAs, and I got it cheap. When I insert the battery bay, it gets hot so I assume it's a short. When I measure between the poles inside the battery compartment there is no short but high resistance. I'm not an expert but I'm now hoping that someone has a clue for me to start finding a solution.

I can solder and fix general things that are reasonably complicated, but I can't see what this might be

Click to expand...

are these rechargable batteries?

RalphLambrecht said:

are these rechargable batteries?

Click to expand...

No, just normal AA batteries. I’ve checked that they are correctly installed and that they give 12v. There’s been some earlier battery corrosion but it’s hard to see how extensive it has been to circuitry. Don’t look that bad.

Open up the unit and start poking around.

tilder said:

here’s been some earlier battery corrosion but it’s hard to see how extensive it has been to circuitry.

Click to expand...

This suggests there may be crud left on the electronics that causes this problem.

There's really nothing else to suggest based on what you've posted; proper diagnosis will involve disassembling the unit and starting with simple visual inspection and some proper cleaning. Based on the findings, see if additional probing around is necessary.

koraks said:

Open up the unit and start poking around.


This suggests there may be crud left on the electronics that causes this problem.

There's really nothing else to suggest based on what you've posted; proper diagnosis will involve disassembling the unit and starting with simple visual inspection and some proper cleaning. Based on the findings, see if additional probing around is necessary.

Click to expand...

Got it, yes, I suppose it's only a matter of getting in there. It cost me about 10$ so it's more a challenge than a loss

Also consider the possibility of “black wire syndrome “, where leaked battery electrolyte destroys the wire inside of the plastic insulator. The wires might look good but not be.

From the Nikon Service Manual for the MD-15.

Without opening it and systematically troubleshooting, all that remains is intuition.

Since normally nothing changes in an analogue circuit on its own, except for defective electrolytic capacitors, faulty mechanical switching contacts and damage due to moisture, heat, force or contamination, I would first start by examining the battery compartment. Corrosion caused by leaking battery electrolyte also continues behind the battery contacts and attacks the circuit behind them, even if everything looks fine from the outside.

The Nikon Motor Drives that I have opened so far are all tightly wired, which means that you should be careful when taking them apart and assembling them.

The solid housings can often only be opened with patience.

I would definitely get the service manual and proceed systematically when troubleshooting by visually inspecting the circuit and using a multimeter basing on the analysis of possible errors. Test points are also listed on the page above making troubleshooting more effective.

When I was assembling an MD-12, I had pinched the positive connection of the battery cable. There was a short circuit to ground (metal housing) and the batteries quickly became hot due to the short.

Perhaps the cause is immediately apparent; I would take a close look at the wiring in the housing. If a component has burned out, there is a cause that must be rectified before it can be replaced.


As always:

All information provided without guarantee and use at your own risk.

BrianShaw said:

Also consider the possibility of “black wire syndrome “, where leaked battery electrolyte destroys the wire inside of the plastic insulator. The wires might look good but not be.

Click to expand...

In this case, the plastic insulation remains intact and the conductor, including soldering points, could corrode inside. In the worst case, it becomes highly resistive, and then no or only a small amount of current flows.

However, a high current flow is needed that the batteries become hot due to overload. This is the case with a short to ground or a component that has become low-resistance.

Andreas Thaler said:

In this case, the plastic insulation remains intact and the conductor, including soldering points, could corrode inside. In the worst case, it becomes highly resistive, and then no or only a small amount of current flows.

However, a high current flow is needed that the batteries become hot due to overload. This is the case with a short to ground or a component that has become low-resistance.

Click to expand...

Thanks Andreas,

This is golden!