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  1. #1
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    Perplexing power problem

    So I was installing parts for a coworker on a Hobart mixer model HL600. The initial problem that my coworker responded to was the bowl would not lift (electric lift). According to him he found 24 VDC gong to the linear actuator but zero movement. He proceeded to order the actuator, rectifier and the rocker switch.

    I went to install his parts today and after reading his paperwork and looking at the parts he ordered I decided to re-diagnose the mixer. It didn't make sense to me why he ordered the switch and rectifier, looks like he was guessing to me. The rectifier ohmed out properly, anode to cathode and vice versa compared to the new one he had ordered. The rocker switch also ohmed fine, as did the linear actuator. So I power it up and I have 24.47 VDC supplied to the actuator but zero movement. Ok, actuator needs replaced.

    I put the new one in and it works! Great right? Wrong... After I have the unit put back together it won't lift or lower the bowl. I take the actuator out to see if the bowl mechanism is jammed. It's not. It's heavy as hell but it moves freely and is not jammed. While the actuator is out I power it up and nothing. Won't budge. Again I have the correct voltage being supplied, measured at the motor leads 23.1 VDC. At this point I put the switch and rectifier that he ordered in. Still no movement.

    I have zero continuity to ground in the entire circuit. Full voltage (211 VAC) being supplied to the transformer, 24.5 VAC coming out and into the rectifier and 24.4 VDC out of the rectifier to the switch. The upper and lower limit switches were working fine but just for good measure I jumped them out to eliminate them as a variable. Still zero movement with the 24 VDC to the actuator.

    Then, all of the sudden, it starts working great! I tried to recreate the problem by moving the wiring around, thinking there might be a problem there but no. I saw something similar once in a Franke Sinfonia. That issue happened to be a solenoid coil had been "absorbing" to much of the amperage. Once the cool was replaced it worked fine. I'm thinking that my wiring or transformer has some continuity to ground and I'm loosing some VA's to ground?? If that were happening would I still have full voltage to my actuator? Maybe full voltage but not amperage to make it move?? This is where a Megger would come in handy.


    Sorry for the super long post. It's just not often that I get this stumped.

  2. #2
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    Dec 2012
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    If you had a short you wouldn't be seeing full voltage to the actuator.

    I assume the actuator is supposed to be 24vdc.

    I've worker on one similar to that unit but it was a bad limit switch so it was easy. Lol


    Sent from my iPhone using Tapatalk

  3. #3
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    >and 24.4 VDC out of the rectifier to the switch

    >Again I have the correct voltage being supplied, measured at the motor leads 23.1 VDC

    Just. Stop. Right. There.

    So, either the switch is dropping 1.3 volts accross it (impossible if there's no load in the circuit), OR more likely, the actuator is being powered fully, but is jammed (not moving) and is drawing down the voltage in the circuit. I'll bet if you had an ammeter in series there would be a goodly amount of amp draw, indicaticating *there is nothing wrong with the transformer, rectifier and switch.*

    Voltage is voltage. If you get the proper voltage to something, you need not look at anything before that measured point. It's good.

    I'll be the actuator over-traveled and jammed at the end, and if powered up in the "reverse" mode, smack it with a hammer it might free up.

  4. #4
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    The actuator was tested out of the unit as stated. Zero load. Nothing jammed. Voltmeter set to DC amps in series= zero current draw. The voltage disparity is due to crappy supply voltage in the area. It's always fluctuating. I've seen it drop from 202 to 177 in seconds at this sight. According to the electric company this restaurant is the second to last customer on this line. This store and the one next door are CONSTANTLY going through motors, compressors even light bulbs. Summer heat waves are the worst.

  5. #5
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    I think your right, voltage is voltage. But if it doesn't have the amperage along with it then it's not going to move the actuator. Plus it's working fine, for now... So it's not jammed. In fact the old actuator works as well.

  6. #6
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    >I think your right, voltage is voltage. But if it doesn't have the amperage along with it

    Measured voltage doesn't *have* amperage. Amperage is a function of load. And if you have excessive load, the measured voltage will drop if the current source (transformer) can not supply the required amperage.

    In other words, if you have a load, and you measure the voltage at the load terminals, and it's near normal, you are flowing an acceptable amount of amperage to power the load. If the load is exceeding the amperage draw available in the circuit, the measured voltage will drop.

    > even light bulbs.

    Now that's odd, because a filiment light bulb will not fail due to low voltage, the opposite is actually true. "Long life" bulbs (in the olden days were rated at 130 VAC. That was the cheap way to do it. Rough Service bulbs are another matter.

    Must be some nasty surges in that power.

  7. #7
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    Forgive me but I'm not seeing where you are helping me with my problem. You seem to be just correcting verbiage. Not helpful. The 5% voltage drop is nominal at best. The zero amps clearly show there isn't a load. Also I would never smack an actuator. That's a great way to break one and seriously mess up the encoder if it uses one. Try spinning the shaft, that's the recommended way to do it. Please keep correcting me while not solving the real issue. Awesome....

  8. #8
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    Mmmmm. Not a good response towards one who took the time to attempt to help.

    Read what you said in your previous post and you'll understand that it didn't demonstrate a proper understanding of an electrical circuit.

    I hope this helps...

    Sent from my HTC0P3P7 using Tapatalk


    "You never know what others don't know." -

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  9. #9
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    Sorru ECtofix, sorry BadBozo. I just didn't find what you said to be helpful. Mostly condescending.

    ECtofix, I wrote the post so it makes sense to me. Can you show me where I lack the understanding?

  10. #10
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    Quote Originally Posted by VanMan812 View Post
    Sorru ECtofix, sorry BadBozo. I just didn't find what you said to be helpful. Mostly condescending.

    ECtofix, I wrote the post so it makes sense to me. Can you show me where I lack the understanding?
    Well, Badbozo explained the volts/amps relationship pretty well, so I won't go there.

    Back to your problem: You had your 24+change VDC applied TO THE MOTOR TERMINALS. The motor should therefore run. Yet, it didn't. You measured zero amps of current, so there was not a complete circuit. Therein, the problem was an open inside the actuator.

    An actuator is DC driven. There's brushes to feed the applied voltage to the armature's commutator. It's far fetched notion - but plausible, that your open circuit within the NEW actuator could've been...say, a poorly seated brush. Yet, with enough jostling of it around while trying to check for jams and such, you managed to gain enough brush contact to get it a connection.

    Maybe there was a speck of dust offsetting that brush just enough so that it initially didn't properly get connected to that particular segment of the armature's commutator.

    Just my thoughts. Could have been something else altogether. These things happen. But...if it's running now, let it ride.

    Ya never know when to stop being surprised by what challenges logic. I replaced an ice cube relay once with a brand new one. The machine still didn't work. Took that new relay's cover off and...it was empty. No coil. No springs. No contacts.


    "You never know what others don't know." -

    If I can't laugh at myself...then I'll laugh at YOU! -

  11. #11
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    It's just weird to have the same problem with two actuators. I put together this exact circuit in my garage with the spare parts (minus the limit switches) and an old transformer and I've been running up and down for hours. No issues. I had a guy with 35 yrs experience come and check it out with me at the site yesterday and he couldn't explain any of it either. Sometimes the actuators worked, both old and new, and sometimes they didn't. Whether they were in the carriage or not. All the while they were being fed 24VDC. Both actuators ohmed the same as well.

    I know I look like a clown here guys. I'm basic saying, "My motor is being fed the correct voltage but won't run, what's my problem?" Lol reading it out loud is hilarious. I guess you shoulda been there because I'm doing a terrible job of explaining the phenomenon it would seem.

    I'm sorry I was short with you BadBozo. Your knowledge is vast and you are very willing to share it. Thank you.

    I'm at this site quite often so I'll be able to keep a close eye on it. If anything happens I'll throw out a post.

    Thank you for the responses!!

  12. #12
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    Which drive do you have..MD,FD,SR??
    Several thing I have run into out in the field on these models...
    (1)bowl up switch with high resistance(full of debris/oil/water)
    (2)T1 transformer output goofy due to burnt connection on L1/L2 on drive
    (3)Bridge rectifier. Always read across diode with a meter that has diode check as this will show the drop resistance of that diode and all should be the close to the same, if you have one that is lower it is bleeding off to ground. Just taking a ohms or tone check across it wont tell ya this.
    (4)Timer board K1 relay failing

  13. #13
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    I thought I'd fill everyone in on how his machine is doing...

    The sight continued to have problems with the bowl lift so they had the local Hobart branch take over the job, kind of a kick in the nuts but what can you do. I spoke with the branch manager yesterday and he told me that over the last six weeks they put 4 actuators in this thing, three brand new and one from an older unit. They were thinking there was a bad batch of actuators so they pulled one from an older unit but it still had the same problems. So, as I thought, the actuators were not the problem. They changed every part in the circuit, one by one, to find the problem. And.... Wait for it..... It was the transformer!!

    He said they always had 24vdc at the actuators but no movement so the transformer was the last part replaced. Before they changed it they ohmed it out with the new one and the readings were the same. BUT, when they put it on the megger the readings were much different. He said they were losing current to ground but had the voltage. I directed him to this page and showed him that that isn't possible lol. Then he laughed at my original post and said "Get yourself a G***amn megger". Yeah probably a good idea.

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