gene cafe not heating up fully

[greenbe]

Hi all,
Just put a new heater assembly in the gene cafe and have noticed that the roasting is taking longer than it used too.l noticed that on the old one there was glue sealing the heater assembly to the top of the assembly with the bottom.What sort of glue is it!
I did a empty run as per avacuppa instructions and the gene will only reach 208.l performed the test run inside so we can forget about ambient temp.The glue is the only thing l can think of .
thanks greenbe.

[KJM]

Re: gene cafe not heating up fully

Oh dear!
Hazbean has been tearing his hair out over a similar problem!

The "glue" is a high temp silicone, BTW.

Hazbeans Gene will ramp up seemingly normally, but then the heating cuts in and out (as it does if the airflow is restricted). Weve swapped out the heater (no help), and the fan (which I was 99% confident would fix the problem..). To no avail, although replacing the fan has made it a "bit" better.

The Gene is pretty simple - so the remaining item that could be at fault is the temperature probe on the RHS.

For Hazbeans roaster - we swapped out the "motherboard" with the one from mine - so it isnt the board

Weve done some measuring of the output of the probe compared to mine, and they seem to be similar (within normal engineering tolerances anyway..).

Im a bit concerned that this seems to be happening to a few people - I like my Gene!

The actual machine is very sensitive to airflow - if you havent cleaned the fan assembly it might be worth giving that a go. You need to remove the fan to do that, but when you remove the fan you are able to also clean the fine mesh filter : When my machine started doing this not-heat-all-the-way-up trick, I got a 100% cure by cleaning the fan.

Cheers
/Kevin

[hazbean]

Re: gene cafe not heating up fully

greeenbes problem may not be the same as mine; it depends on what is happening when the temp stops rising.

When it gets to 208, is there "cycling" of power to the heater? In other words, is the heater "clicking" on and off (if it is, you can hear it).

If so, this is the same problem as mine, but at lower temp. Mine gets to around 230, but wont go higher due to this limiting behaviour. If thats the problem, then prepare for hair loss ... Seriously, in that case I would pack it up and send it to avacuppa, because they have the workshop, the parts and the expertise to go through the process of elimination needed to identify the problem (ie heater, fan, one or the other temp sensor etc). That of course after following KJMs advice re cleaning the airflow path, which seems to be a much more common cause of such problems.

If not, it may be a problem with the heater or its installation.

Others who have installed heaters say that the sealant makes no difference, but I used it anyway. As KJM says, its just high temp silicone picked up from an auto shop.

Main things that I would check then are the joins of the fan to the airflow, and from the heater box to the damping chamber above it. With care, its possible to run it briefly with the case off to check (with the drum in place).

[KJM]

Re: gene cafe not heating up fully

With care, its possible to run it briefly with the case off to check (with the drum in place).

But you should probably ask Hazbean about the need to hastily purchase replacement plastic bits for those melted by operating the thing when not quite assembled correctly :

Ive not experienced interactions with avacuppa, but they seemed very co-operative when Hazbean was trying to debug the problem..

/Kevin

[greenbe]

Re: gene cafe not heating up fully

Thanks for the info guys. l will pull it apart tonight and get back to you. Hopefully it is not a hair pulling exercise.

I think you might be right about the fan. The sensor isnt clicking in. It just cant get to 250.

rgs greenbe.

[KJM]

Re: gene cafe not heating up fully

One small point I forgot to mention - the mesh filter under the fan is actually quite difficult to see properly. When you use a light on it, youll be surprised how dirty it actually is.

On mine, I have to say it was perfectly clean however. But that was because it was sitting under the PCB - I must have got a Friday afternoon build - it came missing a couple of screws and the filter wasnt installed - it was just flopping around in the machine!

Cleaning the fan itself is not easy. What was on mine was (I think) green bean dust. Which is kind-of sticky. Be prepared for a tedious 30mins of cleaning (and dont try compressed air - youll overspeed the bearings in the assembly).

/Kevin

[greenbe]

Re: gene cafe not heating up fully

l cleaned the fan not perfect but a lot better we are upto 234 deg now.l ran the roaster with the cover off to check for leakage on the heater assembly ,l couldnt feel any.l cleaned the mesh on the bottom as well which was quite dirty.lm not sure were these 16 deg are going to come from.
greenbe

[KJM]

Re: gene cafe not heating up fully

234C is similar to what Hazbeans gets to now.... It is also about the point at which my Gene occasionally hiccups.

Does it slowly continue to ramp up? (The temperature will drop a couple of degrees and then rise and will rise slowly back past the previous peak..).

If that is the behaviour, then that is exactly what we see with Hazbeans Gene and Im at an official loss as to how to help.

The only good thing is that if you get 234C, you can at least roast!

Sorry to have run out of ideas...

/Kevin

[Dimal]

Re: gene cafe not heating up fully

Out of interest, does the Gene use a closed loop temperature control, or some sort of profile modelling like the Behmor does?

If the latter, theres a chance that the thermal output of the new element isnt quite the same as the original and therefore the actual temperature may have shifted south of were it used to be.

If the former however, there should be an adjustment (dont know that it would be a PID Controller though, probably just an On/Off Controller) to move the temperature back up to its nominal setpoint. If this isnt an adjustable feature, there is probably a resistor in the front-end of the controller that can be changed out for a different value to achieve the same result.

I wouldnt give up on it just yet and perhaps this sort of thing has happened to others previously (in the UK perhaps) where someone could advise of a practical solution..... :-?

Mal.

[KJM]

Re: gene cafe not heating up fully

Ive not fully traced the PCB and worked out the circuit diagram Mal, but the device is incredibly simple electronically.

The PIC microcontroller (16F877) is one Ive used a fair bit, and the two sensors appear to be RTDs and sit on one side of a resistive divider. Cheap and cheerful. The control loop seems to be a simple PID from what Ive been able to infer by observation. The user input is simply a set-point input and the heater runs flat chat to achieve that. As a heating widget, it doesnt have much spare capacity and this results in a complete lack of burnt beans! The function of the two temperature sensors is not clearly known, but Hazbean has put a thermocouple probe into the LH end of the Gene (the end at the air exit) and the temps he sees on the multimeter agree with what the Gene displays (offset by a fixed amount.. naturally).

So I infer from this that the RH temperature probe is the one that signals something is amiss. I figure the software computes the difference between the two and if there is too big a difference, it calls on a heater shutdown. Likewise if there is too big an absolute value on the RHS, I suspect the same thing happens.

My Gene exhibits the same behaviour from time-to-time and Ive always restored normality by cleaning either the fan assembly or the filter screens in the chaff box. Those require dis-assembly (or compressed air ;D ) to get clean. The thing seems to be engineered with little tolerance for even slightly reduced airflows (which is probably reasonable, given the way it works - the airflow/heating would be a tightly coupled relationship).

Given what weve swapped out on Hazbeans device, I really strongly suspect that the RHS RTD has moved out of spec. Unfortunately, it doesnt seem to be a spare part! It comes with a chunk of the aluminium castings for the heater end of the drum - so weve not tried getting another or dismantling my machine to quite that level to see if that fixes it.

If the part was available, itd be a 10 minute job to swap it in to see!

/Kevin

[hazbean]

Re: gene cafe not heating up fully

Just adding a couple of points to the above discussion, which pretty much says it all.

If the output of the new heater is low, you can check it by using a power meter. With reasonable voltage, it should read in the 1100-1200W range.

The RH RTD (it seems to be a thermistor from looking at behaviour and specs) can be purchased separately -- avacuppa offered to sell one to me for $20. Im thinking about it. The complete unit (basically the Al assembly that sits above the heater) is $40.

Ive attached two pics. The first (found on the web, forget where) is the RH RTD itself. The second is an extract from my logs, comparing behaviour of two roasts before and after I installed the new fan. Its clear it made a difference, but its also clear (from the red line) that the cutout is still limiting heat input. The log is from my TC, which at roasting temps is a consistent +22C over the readout. In other words, mine gets to about 238 before becoming very slow to rise further. The main point here is to observe the "cycling" behaviour -- the amplitude is less than observed when setpoint temp is reached, but still noticeable, and on my Gene is accompanied by obvious clicking from the relay.

[A_M]

Re: gene cafe not heating up fully

The RH RTD (it seems to be a thermistor from looking at behaviour and specs) can be purchased separately -- avacuppa offered to sell one to me for $20. Im thinking about it. The complete unit (basically the Al assembly that sits above the heater) is $40.

That OEM item ie. teh sensor, is the exact same as the ones used in the Sunbeam me thinks (view only).

At room temp if about 97K then I may even have a couple around...

[greenbe]

Re: gene cafe not heating up fully

l might take the gene apart again tonight and remove the fan take it to work and use the air hose making sure that the fan doest spin.You were wright about the green stuff it is hard to get rid of.You are wright about the fine tolerence in the engineering .You would have thought they would have designed it with a bit more grunt.l remember when it was brand new the consistancy of the roast blew me away, l want those days back again.l think it is important that you are able to roast at 250.

[hazbean]

Re: gene cafe not heating up fully

Thanks AM, but this one seems to be a bit outside most found in readily available spec sheets.

I measure it at around 4Mohm at room temp. This is correct, as three (including a new one) have had this value. The LH thermistor measures about .5 MOhm.

[KJM]

Re: gene cafe not heating up fully

l might take the gene apart again tonight and remove the fan take it to work and use the air hose making sure that the fan doest spin.You were wright about the green stuff it is hard to get rid of.You are wright about the fine tolerence in the engineering .You would have thought they would have designed it with a bit more grunt.l remember when it was brand new the consistancy of the roast blew me away, l want those days back again.l think it is important that you are able to roast at 250.

YIKES! Dont blow the fan out with compressed air unless you lock the fan with your thumb first!

You can seriously over-speed those bearings, with resultant need to spend $40 or so for a new one :

When I mentioned compressed air (which every kitchen should come with, IMHO ) - I was referring to the chaff box. You dont need to have much coffee debris on the inner mesh screen to render the airflow inadequate.

AM: the blinking RTDs on this are sharply different in value! I dont know why - if I were designing it then Id use identical components.... Maybe someone had a wharehouse full of them ;D

Itd be handy to know what the actual component is, and how it might degrade over time...

Sigh.

/Kevin