Author Topic: Hotair station microcontroller not controlling ???  (Read 251 times)

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Offline MathWizard

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Hotair station microcontroller not controlling ???
« on: October 17, 2021, 09:10:47 am »
I have a 858D clone hotair station that stopped working. It seems all the external circuits are working, but it won't enable the fan, or turn on the BJT to turn on the AC-opto-coupler. Both BJTs checkout fine. The display lights up and I can move the temp setting up/down like normal, and I can see the MCU talk to the ram chip when you push the button.

But it won't turn on the fan or heater. The LM358 temp circuit seems about as expected, but I don't know if P0.1 is doing what it should be.
hotair station
https://blog.enbewe.de/posts/images/858D/858D_Schematic-big.png
S3F94C4
https://ixapps.ixys.com/DataSheet/PS0315.pdf

I see it has SDA and SCK, there's also a reset pin I wired a 10k onto, but never tried yet. Is there any way to "ask" the MCU if it's ok ? Those pins are in use by the circuit, I'd probably have to pull it, but then what, I have a Buspirate but I don't know programing so I don't know what to do.

I meant to put this under repair
« Last Edit: October 17, 2021, 10:20:23 am by MathWizard »
 

Offline MathWizard

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Re: Hotair station microcontroller not controlling ???
« Reply #1 on: October 21, 2021, 11:11:52 am »
Hmm I thought maybe the temp sensor burned out, it seems it's a PTC at 1.5R at room-temp. Then I thought maybe the schematic was labeled wrong, but no I had the 3pin connectors for the fan VR swapped with the PTC sensor. That makes sense in the op-amp circuit with the MCU setting P0.1

I think I the triac burned out ages ago, because I definitely remember it working, then stopping working in the middle of something. Then ages later I replaced it, and a filter cap too close to it's voltage rating. But I mixed up the connectors, and forgot all about it.
 


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