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Modding the behmor

Postby popeye on Wed Nov 19, 2008 3:53 am

Has anyone replaced the thermostat of the behmor with a variac? I'm tired of mine cycling on and off and I'm tired of having to "preset and guess" using P2. I've been using a variac, but once the P2 kicks to 60%, even 131 volts doesn't do anything. Has anyone opened up a behmor? I'm thinking i'm about to.
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Postby farmroast on Wed Nov 19, 2008 10:08 am

I would not suggest putting more than about 122v through the Behmor or any roaster with circuit boards.
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Postby Marshall_S on Wed Nov 19, 2008 11:34 am

I know very little about electricity but my experience may be helpful here.

I've had a Behmor since it came out about a year ago and I've been very happy with it. I started using a Variac several months ago as a way of manipulating the profiles. Could be coincidental but I've had to replace 3 afterburners in the last couple of months (which is no picnic).

Since I stopped using the Variac I've had no problems.

It could be that I was actually causing mini power surges which kept burning out this part.

Just thought I'd pass this on - I have to agree with farm about being careful with the variac-
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Postby Marshall on Wed Nov 19, 2008 8:51 pm

Marshall_S wrote:...

Uh, oh. :roll:
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Postby shadowfax on Wed Nov 19, 2008 10:31 pm

Marshall wrote:Uh, oh. :roll:


This forum ain't big enough fer the two of us!

Rrrrrrrumble! :shock: :mrgreen:
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Postby ira on Thu Nov 20, 2008 9:40 pm

If you're using a variac on a Behmor I presume it's to lower the temp right ar first crack so I'd guess the right answer is P1 and turn the variac down to lower the temp and never more than 120. As long as the motors are still running I assume it's not too low, just remember to turn it back to 115 when cool kicks in.

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Postby drdna on Fri Nov 21, 2008 1:17 am

A variac will vary the B+ rail voltage for all the circuits in the Behmor. This includes the integrated circuits that run the LED display, regulate the timer, etc. Even if you opened up the Behmor and put the variac ONLY on heating circuit, the temperature is controlled by switching the heating coils on and off intermittently, in essence a simple "digital" on-off system with a negative feedback loop to provide regulation. It is not controlled in a continuously variable fashion to the extent that you assume.

Because of certain tolerances in the circuitry to allow for voltage spikes and surges, it is possible that you can continue to operate the Behmor using a variac, but your results will be essentially the product of bringing the circuit into a state of poor operation.

There is the distinct possibility that you will damage the machine, burn out some parts, or perhaps burn your house down. I would advise against it.

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Postby popeye on Sat Nov 22, 2008 4:00 am

I see not many adventurous people are out there. I'm willing to sacrifice the behmor. Burn it out, burn it down, whatever. Not that it's not a great roaster (and i would probably replace it) - it's just that I want more consistent and better roasts. The machine, barring an explosion that sends molten metal flying, will not burn anything down if it goes up. It is outside the house. I was planning on separating the heating element from the board it's on, and running it directly off the variac. My only question is what will happen to the rest of the machine. Since the element is cycled on and off, I was hoping a short in the element circuit would not harm the machine.

I have had the machine for over a year, and i've been operating it at 125-127v for over 4 months. I only expected to get a year out of it. The interior light has burned out, and the external screws are rusting out (appear not to be stainless). I do live on a beach though (and leave it outside overnight sometimes).
My roasting history has been heatgun/dogbowl, home-made air roaster, home-made drum roaster, iroast2, and now the behmor. I don't really think roasts can get much better than the best roast i've pulled off the behmor. I frequently buy from ecco, klatch, intelligentsia, to compare my roasts. But as consistent as the behmor is, "guess and press" to time first crack and heat reduction means that I have consistency issues - and while all are good roasts, I want all to be great. Yes, a variac and P1 does the same thing, but i can't seem to drop the element low enough after first crack. I assume undervoltage, as well as overvoltage, could damage the behmor. I probably would want to drop the behmor down to about 70-80 volts to simulate the 60% of P2. Has anyone dropped voltage that low? is there any danger?
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Postby prof_stack on Sun Nov 23, 2008 3:36 pm

Until I found an outlet with strong voltage in this old house I tried a variac with the Behmor. The 10A fuse didn't take long to blow. But now all is well without the voltage controller and a consistent 121-122V showing on the Kill-A-Watt.

I don't think the Behmor will take much modding without a fight. I would like a new button put on the front marked FIRST CRACK that you push once P1 gets the beans a cracking. Then the temperature would be lowered a little to stretch out the 1C. That is what P2 is supposed to do, with full power at the end to finish off the roast.

The work around is to use P1 on a bean and measure where 1C begins, and then adjust the initial time or time just after beginning P2 to get the drop-off to occur where YOU want it. The BehmorThing software that Ira worked on is perfect for that sort of thing.
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Postby ira on Tue Nov 25, 2008 2:54 pm

popeye wrote:I see not many adventurous people are out there. I'm willing to sacrifice the behmor. Burn it out, burn it down, whatever. Not that it's not a great roaster (and i would probably replace it) - it's just that I want more consistent and better roasts.


Probably the best way to do that would be to add a couple of switches and a couple of pots to allow you to alter the temperature the control board sees. It's a relatively simple task, but I don't really want to post that info in public as the potential risk(fire) if done wrong is a bit high.

Feel free to contact me off list and if you're not comfortable with messing with wires, I'm just a couple of hour drive from you. My contact info is on the BehmorThing site.

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