Question about Hobart D300 Stand Mixer

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Having problems figuring out what is wrong with my older d300 hobart mixer. Mixing dough the other day the agitator slowed down until it stopped, then the motor just buzzed. It did this twice and the second time I couldn't get it to move again, by hand or by turning it on. It was my weekend and I let it sit 2 days and low and behold it spun again, though when I went to finish my dough (in 2nd gear) it wound down and froze again. My tech says I need a new brass worm gear as this one is concave, meaning worn according to him. The Hobart service man I talked to said the gear is supposed to be concaved and that my gear doesn't show enough wear to be a problem. Any thoughts?

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Could be a bunch of different things. Depending on how old the mixer is, brushes at the back of the motor. If the brass armature is worn down I have been told its too expensive to replace. They haven't used brushes in 25 years. There are a number of bearings that could be going bad. If the main bearings at the back housing or at the gearbox are badly worn, they may be letting the armature come in contact with the windings. If that is the case the motor will be really hot when running. One obvious question is do you have the proper lubricant and have enough of it? Remove the top cover then pop the inspection hole cover off with a screwdriver. The grease inside should be the consistency of heavy wheel bearing grease. If you had a slug of it on a tablespoon it would stay on it if you turned it upside down. It is a food safe grease available at Hobart parts stores. If the lubricant is thin like motor oil, it is totally worn out and is probably not lubing your bearings at all. One other thing to look at is capacitors. A capacitor looks like a large flashlight battery shaped black object with two wires running from one end of it. It is usually located behind the mixer bowl behind a plate held on by two screws. If your mixer has a "run" capacitor, it may be bad. Remove it and head for WW Graingers or such supply house. Get a capacitor of exactly the same voltage and microfarads. Hook it back up and give it a shot.
Back to the bearings. The main motor shaft should have no play at all if you try to wiggle the shaft up, down or sideways. If it does, the bearings are available at industrial supply houses and are not realy hard to replace if you go slow and have a lot of patience in taking things apart and keeping them in the proper order to reassemble.

Posted on Sep 11, 2010

  • mattseverson Sep 11, 2010

    Thanks! There was plenty of grease in the housing, and now I have it mostly drained and have fresh stuff from hobart to replace it with. I'll take a look at that main bearing tomorrow. The capacitor was suggested by someone else, as it's a cheap replacement, and is on the list to replace. The motor is a bit sluggish starting sometimes, and won't turn at all when the agitator is in a certain spot. I haven't noticed it ever running hot.
    Could the worm gear be the culprit, and is it supposed to be concaved on it's profile? Someone keeps telling me it's worn, though the Hobart tech says it's not worn enough to be causing any problems. Looks fine to me, if it is worn it's extremely uniform along the whole gear.
    Once in a while it will stop for a second when running in second gear, i'll hear a clink and then it continues to run. Kinda heart stopping, and not sure what's happening..
    thanks again for the help!

  • vestxre Dec 07, 2010

    D300's did not have a run capacitor they only had start capacitors. Your symptom sounds like the old repulsion induction motor which used brushes to start rather than a capacitor. The brushes are at the rear of the motor. The rear bearing bracket should have two covers that can be removed without removing the entire bracket. If that's the case then you can see the brushes and the commutator that the brushes ride on. The commutator will burn and pit and the brushes will wear out. If the commutator is too bad to clean with sandpaper you can take it to a reputable motor shop and they can turn it on a lathe. If they are not familiar with this type of motor do not let them touch it. Find someone who is. When the brushes are worn out they will be real short and just barely supported by the brush guide. If that's the case they will need to be replaced. If the motor shop does not have the exact size brushes you can buy a set that is larger and very carefully grind or file them down to fit. Make sure they slide freely through the brush guides. If it doesn't have brushes let me know.



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