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I have an ancient 74569 motor:

enter image description here

Unfortunately, it's broken: The shaft spins freely by hand, but when I connect power to it, it doesn't spin at all.

I would like to see if I can just open it and place a new DC motor inside, but without breaking it if possible – has anyone opened one of these before or posted instructions as to how?

I was thinking something like this motor:

dc motor

would fit inside it, but of course I would check the dimensions first and make sure it's not a bad solder joint or something else.

I see Philo has disassembled its replacement here, but I don't see anything similar for the 74569.

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Well, I opened it up without much success, and took some pictures of the process:

At first I tried pushing/prying the light grey tabs away from the dark gray "bottom", but those weren't budging

enter image description here

So plan B: wedge it apart:

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It was opening, but I was also distorting the plastic in the process - perhaps if I had a hot air station or something, I could have of softened it, but eventually it gave way:

enter image description here

I didn't open it just yet, but rather went to work on the other side - I made my way around from the front/back, as it seemed easier than going at it directly from the side. Anyways, it was much easier than the first side, and I got it open:

enter image description here

Nothing fell out, and I didn't rip any wires out by opening it, so I proceeded to take out the motor:

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This is where something finally fell out - there was a little "spacer" disk (visible in the top-left) that was between the end of the axle and the back side of the plastic housing.

After that, the electrical connection assembly slid off easily - not sure what the component is or how to test if it's good, but it seems like it was made such that it's replaceable - no solder was used, just metal "crimps"

enter image description here

This is where I found out that the motor itself is good if I just connect a battery to it directly, so I think I may end up drilling some holes and have a DIY wire coming out the back - all the contacts on the inside seemed good and clean, but unfortunately the bottom seems to be rusted to the point of not making contact anymore.

I think it will snap back together just fine, but it will have scars from the surgery.

For anyone curious, the motor itself is a mabuchi 70586, but any FC-280 motor should fit.

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    You were lucky that the snap fit joints didn't break. I attempted basically the same thing in order to strap a PF plug to such a motor and broke about half of them in the process. Had to use super glue to put everything back together.
    – Shadocko
    Commented Jul 22, 2015 at 16:02
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    Some precisions: the shiny disk is a resettable thermal fuse aimed at limiting current in the motor if it is stalled for a long time. The black cylinder is a 15V surge suppressor, limiting voltage spikes caused by motor brushes.
    – Philo
    Commented Mar 14, 2017 at 15:03

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