Polar Mohr 76 EM will not cycle intermittently

Discussion in 'Cutters and Trimmers' started by vtlco, Jun 8, 2016.

  1. vtlco

    vtlco Member

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    Hi,
    Needing some help on a Polar Mohr 78 EM, unit will not complete cycle intermittently, stuck with blade down position.
    I replaced the 4 clutch carbon brush contactor as they were at the end of their life and I replaced the two cut switch. It work for about a day, now the problem is it won't cycle at all, nothing moves when the cut switch is activated. I can move the clamp by activating the foot control, thats it. I don't have any wiring diagram so I don't know what to look for. All help is greatly appreciated. My email is vtlco1@yahoo.ca
    Thanks,
    Vergil
    (780)-498-0063
     
  2. NimeshSilva

    NimeshSilva Senior Member

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    Hi,
    Did you replace cut buttons with genuine ones? Anyway, let's check the cut buttons first. You have a card called HK in the card rack under the table. It has lot of indicator LEDs. Press the.buttons one by one. Normally V6 and V7 should light up. When you press the right side button, V6 should go out and V8 lights up. With the left button, V7 should go out and V9 should light up. Check it for correct function.

    Did you get any error codes? When you press the cut buttons, is the decimal point (dot) in the right hand side display blinking? If so, press the but buttons another 3 times. Then sometimes you will get an error. Let me know the error.

    Cheers
     
  3. vtlco

    vtlco Member

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    Hi NimeshSilva,
    The cutter still work intermittently, sometimes will not cycle or will not complete its cycle blade stuck haft way up. I also clean the contact for the k21a and k21b relay contact on the KUP card just in case. to answer some of your questions:
    Did you replace cut buttons with genuine ones?(Yes, I replaced it with two new Klockner Moeller switch K10 contacts). You have a card called HK in the card rack under the table. It has lot of indicator LEDs. Press the.buttons one by one. Normally V6 and V7 should light up. When you press the right side button, V6 should go out and V8 lights up. With the left button, V7 should go out and V9 should light up. Check it for correct function.(Yes, the leds light up the way you describe it, when working right) I can't check it now because it is working right now, just waiting for it to hung up.
    Did you get any error codes?(No) When you press the cut buttons, is the decimal point (dot) in the right hand side display blinking?( I did not notice it, I'll watch for it this time). Can you think of anymore thing that I should be looking out for while it is not working right. I also prepared an LED matrix so that I can compare the LED once it hungs up. There are 18 LED's do you have information on what their indication are for?
    Do you have schematic for this unit? if so, I'm willing to compensate. my email vtlco1@yahoo.ca
    Thank you for taking time to lend a hand,
    Regards,
    Vergil
     
  4. NimeshSilva

    NimeshSilva Senior Member

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    Hi,
    While reading your description, I got a feeling that, you have 2 problems.
    1. Knife and clamp cannot be operated at all. You press the cut buttons, just nothing,

    2. Knife get stuck during the upstroke.

    Am I correct?

    It's strange that you don't get any error code. Anyway, in the latter case, you should first check the cam switches. Since the problem is intermittent, probably the contacts of the cam switches might be dirty. Clean them with solvent. IPA will do. If it's not the cam switches, follow the wire coming out of the cam switches unit and you will find a small box which having 2 relays. Sometimes these relays go bad. I have replaced them several times, but I got an error code in all cases. But worth a try.

    Cheers
     
  5. vtlco

    vtlco Member

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    Hi NimeshSilva,

    1. Knife and clamp cannot be operated at all. You press the cut buttons, just nothing,(YES)

    2. Knife get stuck during the upstroke.(YES)
    Is there any commonality in the two problem?
    Yes, There is no error code display.
    Is the cam switch behind the upright frame above the main motor? just behind the anti double cycle solenoid plunger?
    Where is the two relay located physically.
    I'll try to clean that contact tomorrow. is the switch contact accessible like a open relay contact?

    I have another unit Polar Mohr 92 CS s/n 4911242 that is doing the same thing too, intermittently, but this one sometime the blade get stuck on the upward swing only so in seems. I still can't figure this out. we been limping for more than a month now.
    Thanks
    Vergil
     
  6. NimeshSilva

    NimeshSilva Senior Member

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    Hi,
    The two machines have totally different control systems. So no commonality between two. But I still suspect relays. Because both machines are quite old now. Relays have limited number of operations and most probably should be exceeded by now. So it's worth it to change the relays with new, good ones before doing anything else.

    In the EM machine, yes, the cam switches are under the safety bolt (knife locking solenoid) you follow the wire coming out of it and halfway through the wire, you will find a small plastic box which enclose 2 relays. Small one and a wide one. Check them and replace them if necessary.

    Check It out and let me know.
     
  7. vtlco

    vtlco Member

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    Hi NimeshSilva,
    answer to your questions:
    While reading your description, I got a feeling that, you have 2 problems.
    1. Knife and clamp cannot be operated at all. You press the cut buttons, just nothing,
    2. Knife get stuck during the upstroke.
    Am I correct?(Yes)
    Can you think of any commonality in the two above problem?


    Do you know a good source for these old relays? they are Haller Releis brand on the 92CS.
    Thanks,
    Vergil
     
  8. NimeshSilva

    NimeshSilva Senior Member

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    Haller and Erni relays are no more available in the off the shelf market. And if you could find them somehow, they are used ones and much much expensive. So, if you are really into repair it, you have to do a modification here. Panasonic/NAIS NF4EB24V relays become handy here. But the pinout is totally different. So you've to match the pinout and replace.

    You need industrial experience from now on. And please note that I cannot be responsible for any damage to you or your equipment might occur after the repair. Because I'm not the one who is doing the physical work. I'm only supporting you with the thoughts and words. So do at your own risk.

    Cheers.
     
  9. vtlco

    vtlco Member

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    Hi NimeshSilva
    It finally quit on me yesterday. This are my observation.
    1. The Decimal point was flashing.
    2. No error code displayed.(I did not press the cut switch three times, my bad)
    2. LED lights 1,3,5,6,7,12,16 are ON when it hung up, with the cut button relax.
    3. When it hung up I notice that the clamp was in the up position and the blade was in the down position.
    4. But when I manually lower the clamp using the foot pedal and press the cut button again, it will complete the cycle.

    I found the cam switch and the relay box which was tuck inside the electrical tray. I tested the cam switch S 22a, the normally open contact has a high resistance when activated, so I replaced it with a newer style Siemens 3SE5112-0CE01. The old p/n is 3SE3 120-1 E is no longer available so is the contact, it has the same footprint but 1/2" thinner. How critically is the tolerance between the cam the the limit switch roller. there is an illustration on one of the limit switch indicating 1.5mm measured at the highest cam position, is this right?
    I will replace the other cam switch S 22b when I hear back from you, as I don't want to messed it up. By the way I scribe the cam switch to the bracket before I removed it, and I replace it back in the same spot.
    I did not touch the relay yet, I'll try to measure the dry contacts Monday.

    "You need industrial experience from now on. And please note that I cannot be responsible for any damage to you or your equipment might occur after the repair. Because I'm not the one who is doing the physical work. I'm only supporting you with the thoughts and words. So do at your own risk."( I totally understand your concern and I know I'm doing this at my own risk)
    I have industrial instrumentation experience in the oil field, and in my younger year I work for NCR (National Cash Register)
    Thanks again for pointing me in the right direction,
    Vergil
     
    Last edited: Jun 14, 2016
  10. vtlco

    vtlco Member

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    Hi,
    Normally on power on idle, LED 1,3,4,6,7,12 are ON. if the unit will not cycle LED 1,3,4,6,7 are ON only, missing the 12, it will not cycle when both cut switch are activated,nothing happen. I have replaced both CAM switch. dry test the relay K22b there is high resistance on the normally close contact. I'll replace this tomorrow. do you know of anything that I should be checking and what turn on LED#12?
    Thanks,
    Vergil
     
  11. NimeshSilva

    NimeshSilva Senior Member

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    Hi,
    LED V12, that's the point. First of all you make it correct. LED V12 ON means the "light barrier is clear of obstructions". Since the light barrier is not physically fitted with the 78 machines, you have so called "light barrier simulator" fixed to the back side of the back panel board where the cable from the light barrier should fit in. It is a small black box with a brown color connector, located at lower right corner of the back panel board seen from behind.

    I don't think that you have a problem with this little device. If it has a problem, most of the times you won't be able to cycle the blade at all. Since the problem is "intermittent", first you check for bad connection. Take the device out and re insert it several times, this will make the contacts clean. And if you have a better way to clean the contacts, go ahead and clean it. Then check it out again and let me know.
     
  12. vtlco

    vtlco Member

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    Hi,
    I'm not near the machine right now. When you talk about the back panel board is it the Card cage back panel where the cards plug into eg: KUP,HK,KK card.
    Thanks,
    Vergil
     
  13. NimeshSilva

    NimeshSilva Senior Member

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    Hi,

    Yes it is, remove the back cover and you will find the light barrier simulator in right lower corner
     
  14. vtlco

    vtlco Member

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    Hi,
    I found the black light barrier simulator, I tried to re-seat it and cleaned the contacts but I'm still not getting the light to come on. Is there a way to test the module or it there anything I should also be checking also? Is there a way to bypass or jumper the circuit. Now it won't cycle at all a few days back it was just intermittent.
    This is what I did so far, replaced both cut switch, and the two cam switch. I'll replace the inline relay once I resolve LED V12 problem. Could I have done anything to this?
    If the module is indeed defective is it still available. or can I do anything to overcome this or fabricate something only if I know what signal it is looking for. would you have schematic for the module?
    Thanks for your help,
    Vergil
     
  15. vtlco

    vtlco Member

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    Hi.
    I tested the light barrier simulator module on another machine and it is defective. I have already order a replacement module.
    While trying to test the barrier module on another machine, I decided to clean and vacuum the front card cage and the back side of the machine. when I tried to start the cut cycle the machine got stuck. the bade is up but the clamp is stuck half way. I can not activate the clamp even with the foot control. I notice that it blow the F1 6.3 amp fuse it is for the 32 V ac. Can you tell me what the 32vac is used for? and how to isolate it.
    Thanks,
    Vergil
     
  16. NimeshSilva

    NimeshSilva Senior Member

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    Hi,
    Sorry for delayed reply, bit busy on last few days.
    Glad you've found the culprit. The F1 is for power supply for PS5 and PS24 regulator cards. Is it keep on blowing? Then you have to check out what makes the fuse to blow
     
  17. vtlco

    vtlco Member

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    Hi,
    I have found out that the 5 Volt module was blowing the fuse. With no schematic diagram I did a hail mary repair, found out that the output power transistor and the driver was blown. I was able to get the power transistor and have to order the driver transistor. I was also thinking of replacing the two capacitors as they are already old.
    "when I tried to start the cut cycle the machine got stuck. the bade is up but the clamp is stuck half way" do you have any suggestion on where to look. I notice the the paper clamp ram is stuck midway won't retract fully. I don't know if this is related the the blown 5V module? At this time the 5V module is not it yet since I'm still waiting for parts to come in.
    Thank you for spending the time to help me out, you were right of the ball.
    Vergil
     
  18. NimeshSilva

    NimeshSilva Senior Member

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    Hi,
    How about the fuse on PS5 itself? Was it blown too? There is no direct connection from the clamp to PS5. It is only supplying power to the logic circuitry. After you've repaired it, don't directly put it in and turn on the power. First pull out all the cards and power it up alone. Check the voltage and make sure the output voltage is not more than 5.1V.

    Clamp is stuck halfway because the conical value is not open, I think because of this fuse issue. (The conical value should open to return the oil in the Jack to the oil tank) you might see that over night, the clamp will slowly return to the upper position because of the small leakage of the conical value. Then you don't have any mechanical stiffness on the clamp railings.

    If I have the schematics, I would like to give it to you. But unfortunately, me too don't have any internal schematics of the cards. I'm telling you all these through my experience on these cutters. So that is the maximum help which I can do for you
     
  19. vtlco

    vtlco Member

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    Hi NimeshSilva,
    I'm looking for the fuse on the PS5 module and can't find it where is it located on the board? Is it a fuseable resistor type fuse?
    Again thank you for you time and help.
    Vergil
     

  20. vtlco

    vtlco Member

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    Hi,
    I finally found a replacement PS5 module. I've followed your instruction to leave the rest of the board out and check the 5 volt supply from the test point. I'm getting a nominal voltage of around 5 volts. I starter to plug the rest of the module to the card cage one at a time and all is well. I'm still looking for a HK Card.
    Thank you for your help,
    Vergil
     
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