by cynan on Mon Jun 22, 2009 12:07 pm
It is painfully evident that the design of the Gene Cafe's heater unit is just not robust enough. Any sort of build up of chaff residue in the chaff collector or dust build up in the air intake will cause it to wear out over time. My Gene Cafe lasted about 14 to 16 months, averaging about 1 Ib per week until it refused to cycle past 450 degrees with any reliability. Admittedly, I had not been cleaning the inside chaff screen on the chaff collector prior to the failure (did not know it was there) - and maybe had I done so, the heater would have lasted longer.
Interestingly, when I brought this up with the tech at the shop where I bought it (the Greenbeanery in Toronto), he told me that one simple fix was to bypass the heat-activated auto-protection switch inside the heater assembly. This would prevent the heater from relaying the message that it was overheating and not cause the heater to shut off prematurely in the roast cycle.
I took the heater assembly apart, and tried to bypass this switch. The switch consists of two contacts that are separated by a heat-expandable material - when things get too hot, the contacts no longer make - well - contact, and power to the heater shuts off. Strangely, after doing my best to bypass this, things did not improve markedly -but I'm only moderately competent in electronics, so maybe I did something wrong, or do not understand how the over-heat protection works after all... Also, I may have damaged some of the heater elements when trying to reassemble... Not sure.
BTW, for sealant for the heater assembly, I used silicone gasket sealant, available at any automotive parts store. (I think the red tube is rated for at least 500 degrees). I've taken the unit apart since at the sealant seems to be holding up well. I just hope there is no chance of noxious fumes from the sealant mixing with the air that roast the beans, as this might be a health hazard - however, I have not been able to detect any chemical odours that were not there before...
So, now, after that hassle, I'm faced with ordering a new heater for $90. Maybe someone else can post about possible ideas how to disable the over-heat protection circuit, or at least make it less sensitive. I suppose this could be a bit of a fire-hazard, but like all roasting, it should never be left unattended anyway...