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John is an engineer in Texas who is trying to repair his Slide Cube projector himself Derek is an experienced technician in Canada walking him through the repair procedure John: Derek, I'm looking to see if you have an obsolete B&H "slide cube" projector slide advance motor. The motor is a small "slot car" type motor. Do you have any leads on where I might be able to locate the motor or perhaps a used projector I can get to motor out of? Any assistance or direction you can give me would be appreciated. Thanks Derek: Hi John- I just got in a "Junker" but haven't had time to evaluate the parts. I believe the motor is working though. As I recall the user had shaved away parts of the turntable in a misguided attempt to improve transport and I can't get a new one. (The caveat...of course, any advice I give you below is for your guidance only and I take no responsibility for your ability or inability to do any of the procedures safely or to obtain desired results..etc, etc.) Let me qualify something first though. Are you certain that it is the motor that is at fault (I've only seen one die before) or is it the teeth on the little (black, or white) gear that it drives and that engages the turntable? This is more common problem. To check the gear (if you haven't) lift the top cover to expose the turntable. Note the little silver "finger" that is resting in one of the slots on the side of the turntable. When you reassemble, you'll want to fit it in again like that; doesn't have to be the same slot. Now, with a tiny screwdriver, pry off the c-clip in the middle of the turntable, note and remove the tiny black washer, then lift the turntable straight up at the 1:00 o'clock position is the little gear. check the condition of the teeth. This gear is still available, but I don't know the source. There is a company in nearby Toronto that gets them but they cost a fortune. If needed I can direct you later. Now, if you've already gone past this stage and are into the "guts" inside, I'll assume you've diagnosed the motor correctly. (Check that there are no loose wires) While you're in there, look essentially in the middle and you'll see a locking nut on which the shutter blades pivot. This eventually gets sticky as the lubricant dries up. If you feel adventurous, you can disassemble the shutters, clean off the old lubricant and use a very light grease in small quantity when reassembling. If you don't have a very light grease, no grease is preferable to heavy grease. If you do this, note carefully the shape and orientation of the two shutter blades. They are not identical. Also note their position under a crescent shaped metal guide at the edge of the shutter blades. Remove the nut, then gently lift the shutter blades, one at a time. Note a small plastic washer under the first, and usually under the 2nd shutter blade arm (at the pivot point). Note the order in which they all come off. Clean and, if possible, re-lubricate the pivot points. Reassemble. Tighten the nut down to the point that there is some friction, then back it off a little. You don't want to bind the shutter mechanism. This is all to stop the projector from "skipping" slides and/or jamming. (They often jam paper mount slides anyway) When re-assembling the projector, there are 3 things to remember: Be absolutely certain no wires are pinched between the casing and the mechanism or inner casing. It WILL fit together, though it will not appear to until you are very, very frustrated. Do not swear in front of the children when reassembling. You will want to. Now, after all that, if you are certain it is the motor you need, please get back to me and I'll double check the motor I have and fix a price and mailing costs. John: Derek, I took it apart further, though I wished I had waited to read your email as I discovered many of the things you mentioned on my own last night. Yes, I attempted to remove the black lever. I loosened the mounting screws of the solenoid and finally determined, as you pointed out, the black lever was not worth removing. It appeared to move back and forth fine, but now the unit really 'buzzes" when I push the slide advance button. I'll tweak the solenoid position to see if I can get it quieter. Derek: That should do it. You'll have to experiment a little. Look for any tell-tale traces of the original position, made by the washer under the adjusting screws. Use that as a starting point. It's a pain to have to partially reassemble and test and repeat. John: There also seems to be an adjustment of the shutters that I haven't quite figured out, but there is an elegant design of an cam adjuster connecting the metal shutter arm to the black lever. Derek: I call it the eccentric, below. You don't want to touch that. John: I suppose if I ever get to the point of getting the turntable to turn (and stop) smoothly and consistently, I'll be able to appreciate the meaning of that adjustment. Derek: All things being equal, and the shutter blades assembled correctly and closing properly(see below) the eccentric adjusts the blades so that no light shows through when closed. Very unlikely to need adjustment. John: I learned the importance of that black lever and the switch position, this seems very critical (the first time I tried it after reassembly, the table just kept rotating). I think I have the switch position adjusted properly now, so the motor shuts off just as the "finger" begins to slide into the slot. Derek: You've been having a lot of fun haven't you? John: I found a potentiometer limiting the current to the motor so I cranked this for highest motor output and that helped immensely. It still rotates slowly and inconsistently, so I think a new motor and new potentiometer would help. Derek: Hmmm...Are the shutters opening/closing easily now? The locknut can't be too tight. One point of friction that MAY be a problem is where that eccentric meets the silver lever that pushes the shutters. While I wouldn't advise adjusting the eccentric, if you can lift the eccentric carefully to disengage it, clean the little silver "nub" that goes into the eccentric with solvent (WD40 is fine) on a Q-tip. See if you can get a tiny bit of WD40 into the "cup" of the eccentric. Again this is usually not a problem area, but you never know. As for the potentiometer, it's unlikely that it would need replacement unless you are getting irregular gain from it i.e. good contact/poor contact at different points. John: The "finger" that is connected to the black lever sometimes sticks halfway in the slot so the shutters don't open completely. I cannot find any additional source of friction in the assembly so I pulled the return spring and hooked it on the tang a few coils down to give it a little more force, but this may be contributing to the solenoid "buzz" problem. Derek: I've had to do that sometimes too, but I'd turn the potentiometer down a little. Again, only once in a while, do I find one that needs to have the silver "finger" turned ever so slightly from side to side to fit into the slot on the turntable. I do not recommend it as you can get it more out of whack than before. But it may be a last resort. Get the speed down a bit and that should do it, assuming mechanism is not binding somewhere. Just thought of something- when the shutters close, is there any light showing through? If so, try putting the blade that overlaps the other in position so it is under the other. They may close more fully that way. John: I really have a lot of respect for guys like you that work on these elegant mechanical systems. Everything must be timed and adjusted just right or they become temperamental, but that is the way machines like these were possible before digital sensors and timers. It's kind of a fun challenge for me to see if this mechanical thing will beat me. Derek: Frankly, I hate working on them. They were a good concept, poorly executed, with quality of parts and assembly going downhill the last few years of production. John: I'm going to work on it some more this weekend. Thank you for your excellent advise. I'll be writing you again when I've done all the damage... that is... I have explored it further and have decided what to do with it. John: Well, the projector works like new now! Derek: Glad to hear it! John: I located the source of the friction in the turntable assembly. It wasn't coming from the turntable itself, it was coming from the motor & gear assembly. When I originally reassembled it, I used moderate force to push the motor up against the plastic reduction gear. Since this gear has been referred to as the "Achilles heel" of the projector I was attempting to minimize tooth clearance and any premature gear wear. This preloaded the bearing surface between the gear and spindle causing a large amount of friction. I loosened the motor and reassembled it using light pressure on the motor and that speeded things up a lot. I also discovered that the projector itself contained a "spare" motor. I found an identical motor in the autofocus assembly. Derek: That's a new one on me. It never occurred to me. John: Since this had only a fraction of the mileage and load of the turntable motor, I swapped them. It may not have been necessary, but it couldn't hurt. The autofocus motor required a good "solder sucker" to remove the pool of solder from the PC board holding the motor's solder tabs. The turntable now turns swiftly and smoothly. Keeping the turntable at a constant speed, I found, is key to keeping the timing of all the mechanicals just right. After working on the switch timing a little more and readjusting the solenoid to remove the buzz, the projector works flawlessly. I did find that the spring still needed to be stretched and reattached a few coils down for consistent reliability. The spring may have lost some of its force from being stretched for so long. Lesson's learned: Don't apply much force on the motor to the gear when installing the motor. Don't apply much force on the motor/gear assembly to the turntable when installing the assembly Don't ever, ever bend the finger that slides in the slot. Be assured this is not the problem. It will work when the motor speed and switch timing is correct. The timing of the lever switch that controls the motor is very critical. It is adjusted like "points" are (were) in a car's distributor. It must open (shut off the motor) just as the finger slides off the "ramp" and into the slot. When it closes is dependent on the motor speed for smooth operation. Thanks for all your help, Derek! Derek: You're welcome (but you did all the work.)