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  • Hobart 2812 Sometimes spinning backwards

     fixbear updated 1 year, 1 month ago 1 Member · 28 Posts
  • guest

    Member
    September 17, 2018 at 12:00 am

     Hey I have a Hobart slicer model 2812 which is  Sometimes spinning backwards , I did not see the issue myself I ran it a few times and I do not see it spinning backwards the only thing I tested is the capacitor and I found that it is dead can that be a cause of why sometimes it’s running backwards or is there anything else I can check? it is a regular 110v unit.

  • ectofix

    Member
    September 17, 2018 at 6:13 pm

    I don’t know what you mean by finding the capacitor to be dead.  What did your test of it indicate?

  • eritech1

    Member
    September 17, 2018 at 6:35 pm

    I tested the µF . And tested 0 , suppose to be 189-227 

    i installed a new one and hoping that solves the issue!

  • fixbear

    Member
    September 17, 2018 at 6:41 pm

    First I have to know what type of case the capacitor has.  Black plastic or metal.  Second, how did you test it and what did you use.

     

    If a split phase or capacitor start motor, it very well can run  backward with a bad cap or start switch.  If a PSC motor, not likely.

  • eritech1

    Member
    September 17, 2018 at 6:52 pm

    It’s a black round plastic start capacitor , I have A DVM UEi dl429, that u can test µF.

    So I think this slicer has a split phase motor but how does  A bad cap make it spin backwards?

  • fixbear

    Member
    September 17, 2018 at 7:06 pm

    Ok, check the centrifugal start switch.  Often they get spark burns or wear from the armiture and out of adjustment. It is closed for starting.. Unfortunately I don’t think you can buy Flexstones or point files anymore.  So a dollar bill and a little fine abrasive compound is about the best you can do at cleaning them

  • ectofix

    Member
    September 17, 2018 at 7:18 pm

    It’s THIS:

     

     

     

     

     

     

     

    Hobart part number 00-070487-00026 

     

     

     

     

     

     

     

     

     

     

     

     

    Sound like you got it, eritech1.

     

    The only other component to affect the motor start would be the electronic start switch:

     

     

     

     

    Hobart part number 00-271612-00002 

     

     

     

     

     

     

     

     

    Both of those are a PITA to get to to functionally test, so I’d replace BOTH while you’re in there.

     

    Here’s Hobart’s latest manual (2017):

    CATALOG OF REPLACEMENT PARTS MODEL 2000 SERIES SLICER 

  • ectofix

    Member
    September 17, 2018 at 7:24 pm

    I’ve never taken any of the motors apart in OUR 2812s, but I don’t think they have a centrifugal switch in them.  They’re probably an solid state version of start relays for common refrigeration compressors.

  • ectofix

    Member
    September 17, 2018 at 7:30 pm

    Hearing about single-phase induction motors running BACKWARDS has always been a mystery to me.  I’ve worked on MANY motor-driven units, but have never seen it myself.  Therefore I can only suspect the start components as being the culprit.

  • fixbear

    Member
    September 17, 2018 at 8:13 pm

    I can’t tell if that is a current or a potential relay.. But if potential, it has to be indexed dead level to work correctly.  I still have a problem with how you tested the cap.  You can only test one and measure the micro-farads with a dedicated capacitor tester. And they are not cheap.  Hell, I don ‘t even own one.  I can check if a capacitor works, but I can not measure how many uf it is capable of. That requires a very specialized machine/ instrument. You can test with a Ohm meter if the capacitor works, but not it’s value.  First you must discharge it for both safety and test reasons. Then connect a analog ohm meter and watch the needle.  It will sweep from 0 to infinity.  now reverse the leads and it will do it again

     

    To actually measure the capacitor requires a programed power input supply, and a measured load output.  Handheld DVOM’s can not achieve this requirement.

  • badbozo2315

    Member
    September 17, 2018 at 8:17 pm

    Naa, it’s a solid state switch. I’ve let the magic smoke out of a few over the years…

     

    And most good meters these days will do temperature, frequency, and micro farads. Even my little one does DC clamp measurements. Cool stuff…

  • ectofix

    Member
    September 17, 2018 at 8:36 pm

    fixbear wrote:

     

    You can only test one and measure the micro-farads with a dedicated capacitor tester. And they are not cheap.  Hell, I don ‘t even own one.  I can check if a capacitor works, but I can not measure how many MF it is capable of. That requires a very specialized machine/ instrument.

     

    In my twenty years in the military (until 1998), we had Simpson 260s and then were upgraded to Fluke DMMs.  Up until then, the only way I’d learned to test a capacitor was by using the OHMMETER (YOU know that crude method).  Back then, though, my need for testing a cap was a RARE occurrence.  My occupation THEN was working on power generating equipment.

     

    In 1998, I entered THIS trade.  Hence…I’ve always preferred Fluke meters (because of my familiarity with them).  The first meter I bought (in ’98) had a capacitor test mode.  The other prerequisite features it had to have were to test µA (flame sensing circuits) and temperature. 

     

    Later on, THAT meter was replaced by this Fluke 116:

     

     

     

     

    However, for the sake of expedience (and convenience), I’ve never actually done that testing method.

  • ectofix

    Member
    September 17, 2018 at 8:49 pm

    WELL.  The bad-Man comes back from retirement to chime in again. 

  • fixbear

    Member
    September 17, 2018 at 8:50 pm

    That is reactive power.  To really test a start circuit requires a scope and phase angle.  Induction moves phase angle back, capacitance moves it forward. I actually found a improperly installed substation transformer on a power distribution grid that was built different than the other two. Phase angle of A phase was 4 degrees behind where it should have been. Lot’s of motor load unbalance and vibration. Amazing how they suddenly stop talking and involve lawyers when you show a power company engineers that they are wrong. They actually told there employees they could not talk to me.  Yet they provided me a $45,000.00 ABB  solid state motor control to place on the service supply for the plant. I had previously worked very closely with there meter and test personnel.

     

    I know that there are test and meter manufacturing company’s that claim things, but I need to see proof before I believe them.  Knowing what I do about Capacitors, voltage, time, and return all falls into it. I have yet to find a hand meter that will do that.

  • ectofix

    Member
    September 17, 2018 at 8:56 pm

    fixbear, even if I lived to be 150, I don’t think I could ever learn the things you know. 

  • fixbear

    Member
    September 17, 2018 at 9:04 pm

    Oh how I miss my Simpson 260.  I loved that meter.  Wish a fiend I loaned it to hadn’t died before returning it.  But, I do like my Flukes as well.  I use a 87 for the field. A $400 meter with capacitance, but does it accurately measure it.  NO.  I’ve also had the use of a 980, but it is beyond my budget.  I do own a field Oscilloscope and TIF, UEI and belkan meters as well. None approach the flukes for stability,  accuracy and usability.  And the 80 series are as rugged is it gets.

  • fixbear

    Member
    September 17, 2018 at 9:09 pm

    Likewise.  We have both had our life experiences and have learned from them.  It’s the pleasure of passing it on and learning for each other that is the best part. When I was a scoutmaster, The reward of seeing the light come on in a boys eyes with a discovery was one of the greatest rewards a man can have.

  • fixbear

    Member
    September 18, 2018 at 8:00 am

    What you have pictured here is a PSC motor.  Not a split phase.

  • fixbear

    Member
    September 18, 2018 at 10:08 am

    But, let’s explore why a capacitive start, induction run motor runs backwards. To understand this we have to know how the motor is made and why it can run in reverse.

     

    The motor is wound with two or four poles, but also a extra set of winding’s a few degrees ahead of the run winding’s.  The start winding’s have more turns and a finer wire than the run winding’s. Normally the start winding and the run winding get power at the same time. The calculations on where to place the start winding in electrical degrees is different than mechanical due to capacitor charge  time and inrush delays etc.  Suffice it to say that the run winding is almost dead center till there is rotation of the rotor. That gives capacitor time to charge and energize the start winding to create the start torque. Also why start inrush current is 17 times full load run current.  If the rotor winding line up slightly ahead of the run winding and the start is delayed by say a starter contact resistance, the rotor will move to the reverse rotation till corrected by the start winding. Once momentum is developed, if fast enough to carry over a pole the motor will run in reverse. Rarely is that amount of momentum developed, but it does happen.

     

    So from this, we know that if the capacitor starts the motor normally after a reversal the place to look is the start control and wiring. Doesn’t matter whether a centrifugal switch, potential relay or current relay. They all are designed to drop out the start winding at 75%.

     

    I once had a South Bend lathe that regularly would not start without a push on the chuck. Or would start backward.  The reason I dug into this many many years ago.

     

    So, eritech1, you may want to replace the relay

  • eritech1

    Member
    September 18, 2018 at 1:54 pm

    Wow thank you all for taking ur time and helping me, i had no time answer anything yet because I work crazy hours and really hard, I’m sure u experienced that years ago lol.

    but any way I will call the customer back at the end of the week to see if they experienced the issue again and if they do I will definitely put that relay in. I have them in stock so I”m not worried.

    There  are two relays in there the one ectofix mentioned earlier wich is electronic start switch and the black relay.

  • badbozo2315

    Member
    September 18, 2018 at 3:48 pm

    >To really test a start circuit requires a scope and phase angle

     

    I would *love* to get a call at a mom & pop place on a slicer or mixer, and drag out a bunch of meters and a scope, and maybe even a wifi router with all ports with cables in them or something. A satellite dish even.

     

    Spend a few hours fiddling with the knobs, then replace the capacitor. Pack it all back in the truck. They’d talk about it for weeks. 

  • badbozo2315

    Member
    September 18, 2018 at 3:51 pm

    Trying to forget….forget…forget,,,

  • ectofix

    Member
    September 18, 2018 at 5:28 pm

     

    I spit out my swig of beer when I read that.

  • fixbear

    Member
    September 18, 2018 at 7:33 pm

    The electronic start relay.  But just by removing and replacing the spade terminal on it and the cap you may already have solved it.

  • fixbear

    Member
    September 18, 2018 at 7:37 pm

    I don’t know about that cap, but I bet they would be talking about the bill. Tech and knowledge cost money. But will identify the real problem.

  • fixbear

    Member
    September 18, 2018 at 7:38 pm

    Let’s not be wasting the golden nectar now.

  • ectofix

    Member
    September 18, 2018 at 7:51 pm

    Your statement reminds me of this old story that my former boss shared with us techs once (RIP Ray Riggs):

    The Boilermaker Story

  • fixbear

    Member
    September 18, 2018 at 8:43 pm

    I had a fiend that passed about 10 years ago.  He did nothing but troubleshoot Alco diesel locomotives as a independent mechanic..Apparently he was the only one in the world that was good at it and traveled all over the world. Right till his death at 82. I got to work with him once and peruse his manuals. They were well worn, but he held the most complete documentation in existence. He had worked for Alco in the same capacity when they closed down.  And yes, he was not afraid to get his price as there was no competition.  He even had drawings to make what he needed. .

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