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Thread: Cold Sunbeam 6910 thermoblock

  1. #1
    Member nathanharley's Avatar
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    Cold Sunbeam 6910 thermoblock

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi guys, i have tried to search and have found a few posts, but nothing with the answers i'm chasing.

    Im (attempting) repairing my sisters 6910, it has the usual flashing green light that never gets to ready to go phase, from what i have read on other posts, i can be a number of things, thermistors, thermostats, elements thermal fuses or in some cases the PCB.

    After putting the meter on all the components i'm fairly sure that my culprit is the PCB, not to mention it has some dodgy looking tracks on it that look darker than i would expect to be normal.

    If i turn on the machine and allow it to heat up then turn off an unplug, i can feel that the brew block is hot, the steam is stone cold....

    The readings:
    Boiler element - 52.6 Ω
    Steam - 47.6 Ω
    Steam Thermistor - 77kΩ (Checked function by blowing warm air over it, the reading dropped, im told this is normal function)
    Brew Thermistor - 90kΩ

    Not sure about reading the thermostats, ie what resistance they should be if anything at all, i get continuity with both...

    I have continuity with both thermal fuses also.

    I can hear relays at warm up, i feel as though the steam relay is buggered, unless a thermistor is confusing it by telling it its already at temp, but surely i would be able to run the machin but would have wet steam, or cold water as it were?

    Any advice are welcomed!


    Nate

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    Obviously voltage is not getting to the element in the steam thermoblock for whatever reason. If you're comfortable I would test it with it powered up, multi-meter in AC voltage mode and measure across the element, then work your way back and find out which component has failed. Or check the relay first if you think it's that.

  3. #3
    Member nathanharley's Avatar
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    Quote Originally Posted by JoshNZ View Post
    Obviously voltage is not getting to the element in the steam thermoblock for whatever reason. If you're comfortable I would test it with it powered up, multi-meter in AC voltage mode and measure across the element, then work your way back and find out which component has failed. Or check the relay first if you think it's that.
    Yeah cheers Josh, good point. Just wasnt sure how the thermistors and thermostats interacted with the PCB to determine what may be faulty.

    Cheers!

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    Quote Originally Posted by nathanharley View Post
    Yeah cheers Josh, good point. Just wasnt sure how the thermistors and thermostats interacted with the PCB to determine what may be faulty.

    Cheers!
    I would guess if it has a flashing green light indicating it's not ready, then it is getting a correct reading from the thermocouple or whatever sensor is used, and 'trying' to heat. So, that wouldn't be the first place I'd look, it's more likely something between the output of the PCB and the element.

    I'm not even sure how they're wired up but if you follow the circuit backwards from the element and find a relay it should be obvious which pins are signal (relay coil) and which are switched (element). With the machine turned on if there is AC or DC voltage (test for both) on the coil pins you know the PCB is functioning properly at least.

    I'd be interested to see a photo of what you're looking at if you get time! Don't think I've ever poked around in a sunbeam haha.

  5. #5
    Member nathanharley's Avatar
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    So i managed to get my hands on a spare parts machine, it was working just the steam microswitch was RS, so i now have access to any part i need!

    I swapped over the PCB and it now gets to the ready to go phase, but now i also get a flashing red light, and the thermoblock is stone cold, so might swap out the thermistor and thermostat too, just because haha.

    Cheers!

    If anyone needs parts let me know.

    Nate

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    Member nathanharley's Avatar
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    Cool thanks for the pics. Let us know what fixes it in the end!
    nathanharley likes this.

  8. #8
    Senior Member Jackster's Avatar
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    Thermisters- both the same, ntc, 100000 ohm (100k ohm) @ 25
    So if it's warmer, they read less. Waving close to a soldering iron gets around 60k ohm.



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