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Thread: 6910 Stays on!??

  1. #1
    Tassiebean Phil_Jones's Avatar
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    6910 Stays on!??

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi,

    Sorry to be posting so much at the moment, but this is alarming! I've had the sneaking feeling that my 6910 wasn't shutting down, since when I'd come back for another coffee, it always seemed to be still quite warm from the last time (several hours ago!). Well, I connected it up to an ammeter tonight, and it continues to cycle on and off at 5A, about 15 secs on and maybe 3 minutes off. Surprise, surprise! To be clear, this behaviour is when it has been turned off at the soft switch (no LEDs on), but is still on at the wall outlet. The steam wand side remains warm, especially over the ventilation ducts, and keeps the whole top plate toasty warm (!).

    Is this normal? I would think not?

    It seems from the schematic that if the thristor or whatever it is on the main board is permanently failed shorted (on), then it is just the safety thermistor cycling on the side of the steam thermoblock. Certainly, I can hear a soft click and clack as the element turns on and off (follows the 5A on and off).

    Comments?

    Thanks, Phil

  2. #2
    Member peteru's Avatar
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    I assume you've read the manual and it's not something described there, in which case it sounds like it's going in the power saving sleep mode, rather than fully turning off. No such issues with mine.

  3. #3
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    Hi Phil...my machine is over 5 years old and one night I was woken up by the sound of the machine running through some cycle, even though I had switched it off from the machine switch earlier in the evening. From memory, Anger Management advised a faulty thyristor was probably the cause.

    I now take the extra step of switching it off at the wall once I have finished with it.

  4. #4
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    Quote Originally Posted by Phil_Jones View Post
    Hi,

    Sorry to be posting so much at the moment, but this is alarming! I've had the sneaking feeling that my 6910 wasn't shutting down, since when I'd come back for another coffee, it always seemed to be still quite warm from the last time (several hours ago!). Well, I connected it up to an ammeter tonight, and it continues to cycle on and off at 5A, about 15 secs on and maybe 3 minutes off. Surprise, surprise! To be clear, this behaviour is when it has been turned off at the soft switch (no LEDs on), but is still on at the wall outlet. The steam wand side remains warm, especially over the ventilation ducts, and keeps the whole top plate toasty warm (!).

    Is this normal? I would think not?

    It seems from the schematic that if the thristor or whatever it is on the main board is permanently failed shorted (on), then it is just the safety thermistor cycling on the side of the steam thermoblock. Certainly, I can hear a soft click and clack as the element turns on and off (follows the 5A on and off).

    Comments?

    Thanks, Phil
    I'm pretty sure mine goes off properly (using the "soft off" on the control panel). Yours sounds like it's dropping to the standby - which is what mine does if I leave it on - the power button flashes slowly when in this mode and it keeps heat.

    I remember the barrista at our work coffee shop that had this machine had deliberately by-passed his so it did what you were describing - but I don't think it's a standard feature!

    Anthony..

  5. #5
    Tassiebean Phil_Jones's Avatar
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    According to the manual, after 1 hour, it goes onto standby (reducing power to 70% of normal), and the power led flashes red to indicate this. After 24 hours, it then turns fully off.

    I plugged it in this morning, and without touching the soft button panel, all leds are off, but it is drawing 5A. That is, it begins to warm up. I'll have to pull it apart tonight. Eventually, the thermostat would wear out, if I left it that way, to say nothing of the wasted electricity! I'm pretty confident that the thermostat on the side of the steam block is a safety feature, that would only need to operate if something had gone wrong with the control board. That is, the microprocessor should sense the temperature (via its own sensor) and cycle the power to the heating element to keep it at the correct temperature without the "crude" mechanical thermostat needing to do anything. As an aside, the unit also has a thermal fuse on the block as well, so that if the micro fails on and the thermostat sticks on, the block will heat up, and eventually melt the thermal fuse. All round, good, safe, design.

  6. #6
    Tassiebean Phil_Jones's Avatar
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    OK, just to conclude this for any that are interested. It turns out that the control board is very easy to get to. But before that, a WARNING that this information is not to be acted on unless you are qualified to work on equipment like this (and, yes, I am). You undo the four screws in a vertical row behind the back door (easiest to remove the back door first, via its single screw), and there it is. The two thermoblocks are controlled by small 6V coil relays. My steam thermoblock one had frozen short. After desoldering it, of course, it did come better, but I'm wise enough to know best to replace anyway. So, end of the story. Now after I replace it, I'll find out if this has been the cause of my steaming problems!

  7. #7
    Tassiebean Phil_Jones's Avatar
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    Final note - for people qualified to do this type of repair, the relay is part number OJ-SH-106LMH, manufacturer OEG/Tyco. Since this part would not be available from any site sponsor, I don't think I'm a bad boy to let you know where this is easily obtained from: au.element14.com, part number 1891680. Fixed my machine, but not my steaming problem



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