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Large dough mixer acting up -different diagnoses

Posted by marknmt (My Page) on
Sun, Jan 31, 10 at 15:59

We use a fairly old -30+ yrs-, but still very serviceable, Boku two-speed spiral bread dough mixer. Recently we started experiencing an intermittent symptom which also occured several years ago, and was promptly, and easily, fixed in short order.

As I understand it this is a three phase, 240 V motor. It's easily capable of mixing 250# of dough in second speed. It looks like a giant mix master. The bowl is about four feet across and over two feet deep.

The symptom is that when we turn it on from the OFF position to the "1" position it makes a groaning sound that I associate with the motor not getting enough voltage to operate correctly, but still getting some power. We can readily replicate the sound by switching it to an "in-between" position between "1" and "2".

The motor performs flawlessly in second speed, and if you switch it down from second to first it is also fine, albeit the shift makes a considerable "clunk" -always has.

Last time we had the problem the tech swapped out some relays. They were readily accessible at the top of the mixer and it took maybe 45 minutes.

But an electrician that we've used before and is who is great with most stuff can't find anything in the relays and switching and says we have to pull the motor.

I didn't let him do it. Was I right to look for another opinion before doing a major motor repair? Or do I need to bit the bullet and get along without the beast for a week or two?



Follow-Up Postings:

RE: Large dough mixer acting up -different diagnoses

How is the speed change created?

Mechanical gearing with a solenoid?

3-phase motors are single speed devices unless you vary the number of poles in the motor, or use a modern device like a variable frequency drive that it seems unlikely for this equipment to use.

Once you determine how the speed change is implemented you can look into how to fix it.

Gears and a solenoid would be a likely method for older equipment.

RE: Large dough mixer acting up -different diagnoses

You should contact a mixer dealer and repair facility, preferably one that deals in that brand of mixer. 30 yrs is not that old. These mixers are routinely bought and sold and refurbished and repaired in between.

If you can find the tech who fixed it last time, that would be best.

RE: Large dough mixer acting up -different diagnoses

Thanks, both of you.

We did have a mixer repairman look at it- the Hobart guy was able to get right to us. Looks like a new speed selector, which will have to be shipped from Germany and will cost about $400 plus shipping, and take up to a day of the tech's time. All told could be close to a $1200 bill!

For anybody who's curious, it's a Boku SK 160 A, 220V 3 phase. I get confused about 220 vs 240, so please make adjustments as needed!

Hendricus, I'm sorry to say that the tech who fixed it last time tired of his employer and decided to buy a bar instead. But the guy who is working on it has a lot of experience and should do well.

The tech mentioned "overload voltage" or something to that effect. I don't know if it has an actual transmission; it very well could have without me knowing it. I did get the distinct impression that it involved a change of motor speed, but I get a lot of things wrong.

Thanks very much again.

Amazingly, beyond replacing relays and belts, there have been no other issues with this machine in spite of heavy use for most of those 30 years. Well, it needs a timer, but we're afraid to ask the cost ...

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