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IKA mag stir plate/hotplate, "RTC" some info...

Discussion in 'Electronic Repair' started by William Beaty, Aug 16, 2013.

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  1. Also find info below at: http://staff.washington.edu/wbeaty/chem_stir.html


    Those IKA-Works stirplates cost upwards of a $1K. So, yes worth repairing.. We see lots of these, mostly with buffer/saline spills, or the DPST power switch has died. For the more involved fails:


    The quick cheap fix is: replace the entire guts, two PCBs with
    a permanent ribbon between, Part No. 5008001, PCB Assy for
    stirplate number RTC-B-S1 $156.00 (2012 price)

    IKA Works
    2635 North Chase Pkwy SE
    Wilmington, NC 28405-7419
    Phone: (910) 452-7059


    See PCB Photo w/notes: http://staff.washington.edu/wbeaty/stir3.jpg



    Safety shutdown

    The LM358 dual op-amp compares the setting of the safety-temperature pot with the output of the main sensor thermistor. If the two values approach tooclosely, or if the safety pot is set too low, the op-amp will drive the base of the SOT23 BC817 (NPN transistor) low to shut off the safety relay; removing 120VAC from heater.

    A second BC817 NPN in series must pull the above NPN's emitter to below approx 5V in order to drive the safety relay on. The second BC817 is driven bythe Q-output pin5 of the 74123 retrig 1-shot, which is kept constantly high-triggered by the LED scan signal from the CPU. And, its own emitter in turn is pulled low by being connected to the 5pin DIN's pin3. The pin3 mustbe grounded in order for the rest of the circuit to drive the safety relayto supply 120VAC to heater (you must add a jumper between pin3 and pin5 onthe rear DIN.)


    Common error msgs

    ERROR-6: Missing temperature probe. You must enable the stirplate by installing the LCD thermal probe assembly, or the small grey jumper plug. Or, just ground pin-3 on the rear connector by using a bent piece of solid wire #16ga to jumper from pin-3 to pin-5. See pin diagram on the PCB photo above.

    ERROR-25: Processor thinks it can't turn triac on/off, or no AC at heater/triac section. Caused by: heater-coil failed or unplugged, or the triac or heater relay is dead, or the safety-relay is forced off (because of 1K thermistors wrong or unplugged, or safety-tempr pot set wrong, or the DIN connector's shorting-plug missing.)

    User manuals (no, not service manuals)
    http://www.ika.com/owa/ika/content.service_manuals

    IKA Works catalog page
    http://www.ika.com/Products-Lab-Eq/Magnetic-Stirrers-Hot-Plate-Lab-Mixer-Stirrer-Blender-csp-188/
     
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