Fan Won't Shut Off


 
B

Bob C

TVWBB Member
I put together a Ver 4.3 board. I also have a microdamper. On my first cook everything worked great. The temp went to my set temperature and leveled off within a couple of degrees. It then stayed within 5-10 degrees the whole 6 hours of the cook.

Earlier today, I was working on my second cook and the temp went right through my set temperature of 250. It went to 300 and I went to figure out what was wrong. The fan was running full speed even though the GUI said it was supposed to be shut off. While I was trying to cool the Big Green Egg down I did some quick troubleshooting.

The servo is working correctly. No matter what the temp was set on 250, 0%, 100%, the blow pin of the network jack was always a little over 12 volts. I hooked it back up to the egg but pulled the fan power wire on the jack so I could use it in servo mode. I'll do some more troubleshooting when this cook is done.

I didn't make any changes to the HeaterMeter between the cooks.. What could have changed and were do I start looking for the issue?
 
Interesting. Did you use the heatshrink provided in the kit? You said the servo was working properly, so the damper should have been closed fully while you were way above temp, but the fan was still blowing full? I imagine that could possibly suck in enough air to get a kamado running high, but I'd think it would take a while, unless your top disc wasn't tightened enough.

Perhaps someone who has better experiencing reading electrical schematics could trace something down to give a specific spot to check - I am not an EE nor do I attempt to be.
 
SteveCK, I did not use the heatshrink tubing but have pulled the microdamper housing apart and verified none of the wires are shorting. Also I disconnected the network cable to the microdamper and still have the 12v on the blower pin on the board.

John Bostwick, I've gone over the board again and can't find any extra pieces shorting anything out. I have also lightly scrubbed the whole board with a dry toothbrush.



Checking the voltages of a few components on the solder side of the board with the power connector on the left side I get the following voltages. The numbers are for the pins left to right

Q1 1.7 , 0, 0

Q3 12, 12, 1.7

Pin 5 (blower) of the ATMega chip bounces between .001 and .003

Should I be getting 12v on the right pin of Q3?
 
You could try changing over to Pulse Mode for the blower in the HM config, this will help you determine if the issue is in the blower driver or feedback portion of the blower circuit. Below is an image I put together to aid in troubleshooting the blower circuit. It is showing the V4.2.4 board so the layout is gonna be different, but I believe the blower circuit is the same on V4.3 so the voltage references may still be useful to you...

HM_Blower_Notes.jpg
 
Like I said, it at least gives you an idea what the voltages should be on the transistors, you'd have to trace out the component locations on the V4.3 board yourself. Or did Bryan change the blower drive circuit on V4.3? (other than to move components locations)
 
I reflowed the solder on some of the components and still having the same issue. I'm not sure what to do next
 
Nothing is impossible, transistors can overheat during soldering... Also, look at the part number on the transistor and make sure it is right, mix ups happen too...
Unfortunately I haven't built a v4.3 board so I can't be much help to you, beyond to say you can measure the voltages on Q1/Q3 while the HM is at 0% and 100% (with the fan config set to Pulse mode) and compare them to the notes I have on the image above. (they will be the same on the v4.3 board)
If this is a new build then you should also be looking for a solder bridge around those components, if you post some closeup pics of the boards maybe somebody will spot something you are missing...
 
RalphTrimble said:
Nothing is impossible, transistors can overheat during soldering... Also, look at the part number on the transistor and make sure it is right, mix ups happen too...
Unfortunately I haven't built a v4.3 board so I can't be much help to you, beyond to say you can measure the voltages on Q1/Q3 while the HM is at 0% and 100% (with the fan config set to Pulse mode) and compare them to the notes I have on the image above. (they will be the same on the v4.3 board)
If this is a new build then you should also be looking for a solder bridge around those components, if you post some closeup pics of the boards maybe somebody will spot something you are missing...
Click to expand...


I finally got motivated to troubleshoot some more. The Q1 is a BS170.

It doesn't matter if it is set to pulse or voltage or set at 0% or 100%, pin 5 of the ATmega chip bounces between 0, .002 and .003.

Any thoughts on why pin 5 doesn't chqng voltage?

IMG_0489_zpsq5vj1hcj.jpg
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ATMega Pin5 should go from 0-3.3v, so definitely a problem there. Couple things that could be going on.... Q1 could be trashed from being overheated during soldering, or one of the legs of Q1 could have a solder bridge to the ground plain (only one pin of Q1 should be ground), same for Q3, I would trim back those legs on Q3 and make sure they are isolated from the ground plain (none of the Q3 pins are ground). Could also be bad/incomplete flash of your ATMega, you can reflash that to be sure.
If Q1 turns out to be bad you can steal the BS170 from the buzzer circuit, everything else will work, the buzzer just wont sound.
 
I got it fixed. Turns out the middle lead came out of the body of Q1. Replaced Q1 and all is working again.

Thanks everyone for the help.
 
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