Quest M3 fan not working?

Discuss roast levels and profiles for espresso, equipment for roasting coffee.
sternocleido

#1: Post by sternocleido »

Hello again!

I am getting to know my shiny new M3 roaster, and have another question. I have read countless posts on air flow, and seen a video on it on youtube (https://www.youtube.com/watch?v=HxhbQmuO8yI). It seems that fan speed control should give me a granular control of my various temperatures - but I have been perched over my roaster for the better half of yesterday's afternoon, and could not get *any* change in *any* temperature by adjusting the fan knob. I have cleaned every conceivable part of the fan, and still nothing. Finally, in my desperation today I tried to set the fan to full and adjust the inflow by opening the chimney door to various degrees - and voilá! Almost instant minute control of the temperature! Open the chimney (ie stop the air flow), BT ramp slows down and MET increases; close the trap door and air is pulled through the roaster, BT increases and MET decreases. So as far as I know - everything is as it should be, although holding the trap door in various positions by hand is rather tedious...

Does anyone have a clue why the fan knob adjustment does give me the desired results? I can see the fan rotating and I can hear slight difference in speed between 0 and 9 settings (although it is rather subtle). By putting my fingers into the chimney I can feel air being pulled through the system, but cannot feel any perceivable difference between max and min settings. Is there a way to increase this difference?

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another_jim
Team HB

#2: Post by another_jim »

My fan stops completely at around 3. It looks like the dimmer circuit on your is out of whack.
Jim Schulman

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sternocleido (original poster)

#3: Post by sternocleido (original poster) »

As far as I have read, older M3's fans stopped completely around 3-4. But the newer models have been altered to keep the fan on even at the lowest setting. However, I would think that the change in speed should have been much more significant than it is in my case.

I took a look at the circuitry, it looked rather messy to say the least. I am slightly cautious about tampering with it... Does anyone have some kind of schematic of the internal wiring?

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another_jim
Team HB

#4: Post by another_jim »

On mine, it's an old school triac circuit, all soldered onto the pot's leads themselves. Changing it would involve changing one of the fixed resistors. Sadly, I don't know the exact details.

A simpler, but less elegant approach might be something to block and unblock the rear exit vent. That would probably give you less drastic, more adjustable control than manipulating the bean chute.
Jim Schulman

sternocleido (original poster)

#5: Post by sternocleido (original poster) »

Thank you, I'll get out my trusty multimeter then, and do some research...

In the mean time I chose a slightly different approach than blocking the exit vent... I put a small piece of folded aluminium foil behind the trap door on the chimney. You can slide it up and down to control opening of the pipe leading to the fan. I have also made marks on the foil where it allow the opening to be 0/25/50/75/100%.

Besides controlling the air flow this has the added advantage of shielding the horizontal pipe when charging beans in the beginning of the roast so that they don't end up in the pipe instead of the drum. Works like a charm!

Here are some pictures:

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another_jim
Team HB

#6: Post by another_jim »

Even better.
Jim Schulman

sternocleido (original poster)

#7: Post by sternocleido (original poster) »

After doing some more googling, I found this thread: http://www.kaffee-netz.de/threads/quest ... ung.84946/

It links to a document originally sent by Molly. Here is an excerpt:



So, you only need to cut the 300k resistor in parallell with the trim pot. I have just made the modification and can report that it works like a charm! :D

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Goldensncoffee

#8: Post by Goldensncoffee »

Very interesting. I have a newer Quest and the fan works the same way. I would love more control over it. Let us know if you cut that wire and what happens.

Edit*** just saw that you did it at the bottom of the post....awesome !

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FotonDrv

#9: Post by FotonDrv »

Great information! Thank you for the Posts :)
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Md ca

#10: Post by Md ca »

sternocleido wrote:After doing some more googling, I found this thread: http://www.kaffee-netz.de/threads/quest ... ung.84946/

It links to a document originally sent by Molly.

So, you only need to cut the 300k resistor in parallell with the trim pot. I have just made the modification and can report that it works like a charm! :D
Thank you! I made the same mod to my Quest, and it is now a different roaster.

Thanks, Maureen