Bell & Howell AF70 disassembly

Mabry Tyson
6/26/02
For more info on slide cube projectors, please see John DuBois's site

These images show the insides of the Bell & Howell Slide Cube Projector AF70 as I worked on it to get it working. I hadn't used it in years and it was having problems with not stopping at slides. I was able to get it working properly, without destroying it.

Tools you may need

Make sure the projector is unplugged and has cooled down before taking it apart.

P6260427 It took a while for me to understand how to take the projector apart. It was easy to get the turntable off but I didn't really need to and I didn't need to get under it. You just pop the e-clamps off (be careful, they could spring away). Don't forget the washers, especially the very small one on the pivot of the turntable.

P6260435 P6260434 The key was to get the left hand side off (not difficult), exposing a 3/16" hex-head bolt (with lockwasher). That bolt plus the four screws by the turntable attach the bottom of the projector. I don't think it matters what order you take these out.

P6260415 I found it easier to take off the cover that gives access to the bulb. Then just work the bottom away from the projector. The front and back covers of the projector body may fall off.

P6260416 I had some false starts here, but what you should do next is to take out the bulb by using the lever that lifts it up. Then there are 5 screws to take out the bulb assembly. It will still be attached by wires, so just set it aside.

P6260417 There are three screws to take out the fan assembly. One of those had a wire that is used to restrain the other wires. You'll need to remember to put it back on when you reassemble. Again, just set it aside.

P6260418 P6260421 Then it was a simple matter of removing the locknut and lifting the shutter pieces out, taking care to remember the order. I had already taken off the spring that puts tension on the forked piece. I then worked the forked piece out from under the cap (behind the wires in this picture) that holds it in place near the microswitch, and removed it.

P6260420 Once I had the shutters out of the projector, I cleaned them off with first with alcohol (and then turpentine because I had it handy). They weren't too obviously dirty. The only lubrication that they seemed to have was where the washers were that separated them. There was no sign of lubrication on the black shutter part. I also cleaned the washers.

I found that the outermost, trailing end of the left hand shutter (top left hand corner of it in the the image) was tweaked. If I ran my fingernail over the end, I would catch the metal. I first straightened out the metal as best I could by pressing with a piece of plastic (flashlight) on the shutter while it was on wood. This made it better, but it would still catch my fingernail. I took some flat pliers (jeweler's pliers, not ones with ridges on the flat face), placed the tweaked corner as close to the plier's pivot as I could, and then squeezed hard. I did this twice, one 90 degrees relative to the other. This seemed to make the piece feel smooth to my fingernail.

P6260410 I don't know what happened that could have caused this. Possibly the lock nut was loose enough that the shutter twisted enough to catch that edge.

P6260422 I also took out the forked piece that runs from near the solenoid to the shutters. I cleaned the posts on them (2 at one end, 1 at the other). This seemed to have a slight bit more old grease than the shutters themselves.

P6260413 I also cleaned the pivot post in the center that the shutters fit onto.

I then put a hint of white grease on the shutters around the pivot hole and the holes for the forked piece. I took the smallest amount of grease I could get on my little finger, put it on the hole and turned things so it spread all the way around. I then to a relatively clean thumb and index finger and basically wiped the grease off in the same manner. So there was very little grease left.

I also did the same thing for the washers, the forked piece, and the pivot post. I also put a small bit of grease on the top side (the underside as shown in the pictures) of the forked piece where it might rub against the projector.

P6260423 When I reassembled everything, I was careful to make sure the end of the shutters were under the metal cover at their end (held in place by two screws). They slide on a raised ridge. I saw no evidence of lubrication there, so I didn't touch it.

Make sure that all the washers and shutter pieces are assembled in the right order. I had felt that the shutter pieces were assembled too loosely before. I tightened down the locknut until I could no longer move the shutters. Then I loosened it up slightly until things moved. Then it seemed I could tighten it down a bit tighter than before. This time, once it stopped moving, I loosened it about 1/16 of a turn. The shutters moved freely.

I had unwisely adjusted the screw that is closest to one end of the spring, thinking it would increase the tension on the spring. Bad move. Getting it adjusted right again was difficult.

P6260424 P6260425 I thought it would be correct to set the position so the microswitch closed (i.e., its two blades touched each other) at the position where the finger that stops the turntable was as in this picture. In this position, the shutters were as shown.

This was too tight. The turntable never turned because the finger never released. I had to change a bit from that.

I put the spring back on. I was tempted to find a tighter spring or to hook it a couple of turns from the end, but I didn't. It all worked fine anyway.

I took this occasion to clean the dust off the mirror by the lamp.

Reassembly of the insides was pretty easy. You are screwing metal screws into plastic, so don't use too much pressure or you'll strip the threading. I suggest you get all the screws started before tightening any down too far. Get them all somewhat snug before tightening any of them too much.

Don't forget the short wire to restrain the other wires that should be under one of the screws on the fan assembly.

I then CAREFULLY tested the mechanism. I am comfortable working around open electronics but if you're at all uncertain, don't test until later. Be aware that the fan will spin and might hit your work surface. I made sure all the tools and other metal objects were away from the projector before I plugged it in. After testing, I unplugged the projector.

The trickiest part was getting the sides on the projector. P6260430 If you put on the bottom all the way, then you can't get them in place. But without the bottom, the sides just fall off. So you need to put the bottom on the projector. Be careful here not to pinch any wires and to make sure everything fits properly. It was a bit of a tight fit.

P6260431 P6260432 I had taken the hinged cover (where the on/off switch is) off and it needed to be put back on. The picture shows me attaching the hinged cover with the bottom partly on. Then you need to make sure the bottom of the right side fits inside the rim on the bottom cover. This was a bit tricky.

P6260433 The front and back covers need to be tilted on as shown.

Reinsert the four screws and the nut with lockwasher and replace the left hand side.

If you haven't already reinstalled the bulb, do so now.

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