Lincoln 369155 Oven Conveyor Control Board

Discussion in 'General Electronics Chat' started by tracecom, May 15, 2014.

  1. tracecom

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    I have a friend (cousin, actually) who has opened a pizza parlor. His ovens were used and, after only a week or so of operation, are both down. In both cases, the oven conveyor control board has failed. He has three boards, which he says are all defective in one way or another.

    Because he has exhausted all other options, he is bringing the boards to me in the morning. I have the service manual for the ovens: Lincoln 1000, but I don't have a schematic for the 369155 conveyor control board.

    Any input or advice would be appreciated.

    Thanks
     
  2. THE_RB

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    Check the motors to see what type they are.

    You won't always need a schematic to fix a motor driver PCB because often the faults are very obvious like burnt out power components. But it will be really handy to know if they are DC motors (ie treadmill style) or brushed universal motors or shaded pole type motors.
     
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  3. Alec_t

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    Judging by this pic of the board you might get lucky without a schematic, as RB says.
    http://ep.yimg.com/ca/I/yhst-58676777550784_2273_245582110
    Things to check first would be the fuses, the big cap and the semiconductors.

    Edit:
    The board looks as though it would be relatively easy to reverse-engineer to draw the schematic if necessary.
    From the service manual it seems the control board provides a variable DC voltage to the conveyor motor for speed control. Depending on serial number there may or may not be a tacho for speed feedback.
     
    Last edited: May 16, 2014
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  4. tracecom

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    The motors are DC. Here's the explanation from the service manual of what the oven conveyor control board does.

    Closing the fan switch and the normally open conveyor switch supplies 120 VAC to the Motor Control Board. AC volts are converted to DC volts and are supplied to the Conveyor Motor at terminals A+ and A-. Adjustment of the Speed Control Potentiometer (5,000 ohm 10 turn) will change resistance at terminals P1, P2, and P3 varying the DC voltage to the motor. The speed of the conveyor motor will increase or decrease as the DC voltage from the board increases or decreases respectively. As the motor turns, it drives both the reducer gearbox and the tach.generator. The tach. generator is a DC voltage generator which supplies a voltage to the DC motor control board and is used as a reference for maintaining a constant conveyor speed.

    Thanks for the responses. I am afraid that one of the motors may be bad, which is taking out the control boards.
     
  5. Alec_t

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    That description applies to Model 1000 units with a Serial Number >=4390. Earlier units have no tach generator.
     
  6. MaxHeadRoom

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    It is relatively easy to test the motor using a automotive battery to test both directions, as Alec_t mentions the board does not appear to have tach connections, the sign of a large cap and only two power devices points to a PWM controller rather than SCR.
    Max.
     
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  7. tracecom

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    Yes. I think that's what I am going to be dealing with. The attached (hi res) photo shows one of the boards actually installed in the oven; it has the A+ and A- terminals, which I believe ID it as a unit with a tach generator.
     
    Last edited: May 16, 2014
  8. tracecom

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    The board has a couple of A69104 SCRs, but I can't find a datasheet for them.

    ETA: The 14 pin IC with a sticker on top is an LM2917N voltage to frequency converter.

    (This is what I learned from talking to my cousin on the phone last night; he is bringing the boards this morning. I won't have access to the actual ovens without making a road trip...which may be necessary.)
     
  9. MaxHeadRoom

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    Hmm a Large cap usually is only required for PWM types and the LM2917 is a digital to analogue convertor.
    [​IMG]
    Max.
     
  10. tracecom

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    I don't see a transformer on the board to step the 120VAC down to 12VAC. Any idea on that?
     
  11. MaxHeadRoom

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    In most it is done with a simple zener/resistor/capacitor set up.
    Max.
     
  12. Alec_t

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    Agreed; that board looks to have the tacho function, handled by the LM2917 frequency-to-voltage converter. More complex than the earlier non-tacho version I linked to :).
     
  13. Alec_t

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    There is space for one, marked 'T2', but presumably R25 now drops the Volts instead?

    Edit:
    Pages 27-28 of the manual have some useful trouble-shooting tips.
     
    Last edited: May 16, 2014
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  14. tracecom

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    Probably. I haven't seen the motor, but I just assumed it drew a couple of amps...maybe not.

    At any rate, I just got a call for my cousin. He has found a replacement board within driving distance, so won't be bringing the bad boards here today. When I get them, I will post again.

    Thanks to all for the help. :)
     
  15. Alec_t

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    Best he checks the motor before installing the board; otherwise you'll have an extra one to fix :).
     
  16. tracecom

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    I warned him about that very thing.

    ETA: Just got word that the replacement board didn't work.
     
    Last edited: May 16, 2014
  17. THE_RB

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    It uses dual SCRs (phase angle controlled) and dual fixed rectifiers (grey diodes) acting as a controlled bridge, going to a large cap (to approximate DC), then to the motor. :)
     
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  18. tracecom

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    I missed those. Thanks.
     
    Last edited: May 17, 2014
  19. tracecom

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    I believe you are correct. In the service manual, it indicates that the voltage to the motor is DC, but is 150 to 160VDC. Thanks.

    And again, thanks to everyone who posted. At least I now have some baseline information, and I feel certain that I will eventually need it. :D
     
  20. MaxHeadRoom

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    I realize how an SCR bridge works, it is just very unusual to see such a large cap on SCR drive, these are more common on the PWM versions.
    The KB/Baldor drives and other makes of this type typically never use a capacitor after the bridge, at least not on any of all the makes I have installed.
    Max.
     
    Last edited: May 17, 2014
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