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Help with circuit troubleshooting


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Hi, I am new to this so any help would be appreciated. If you want me to post to some other category pls let me know.  I have a circuit with relay, some resistors and capacitors, diodes and a transistor. The circuit has problem as the relay doesnt click and the dehumidifier doesnt start. I tried the relay on this circuit on another one and the relay works fine, so its not the relay that has issue. Diode seem to be ok they conduct one way (could there still be some potential problem  even though they show working ?)

I am not sure how to test the other components, I tried testing the resistors and they all seem fine and show me a value on digital multimeter. How do you test all the components on a circuit, i read it suggested that the components be tested outside the circuit, certainly with so many components they cant all be taken out of the board and tested ?  what else should I check and what could be wrong here...


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ok I will post some layout /sketch. I dont have a complete schematic but I will post some stuff and pictures of the circuit soon.

btw, the humidistat is external and is a mechanical one. when I tested the other circuit (the working one) the humidistat clicked and the dehumidifer worked. When I attached this circuit back, nothing. The relay on this one is good I checked it on the other circuit.  There is one IC on this which I suspect ,

its 12C5028A (probably a re-programmable IC?).

1 Tanssistor is C556B

4 caps (one of them is 47uf 63v, others are small ones)

will post more details and pictures soon.

Thanks for your help in advance.

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Sorry I misplaced my password and the system here does not send password when you forget it, no email sent. so had to get another id.

I couldnt find any circuit diagrams and am attaching some pictures of the circuit to start with.
A few notes

Input from the unit is AC 110/120v

Relay tested is ok

Transistor when given small voltage on emitter and base it works and the relay clicks manually. so transister seems ok.

I guess the diodes on the circuit are used to convert to DC voltage since relay is 24v DC. ?

Checked the Capacitor, shows 54 volts DC across the big one.

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attaching another picture, labels on this one are much clearer. If you need any other view/picture from another direction/angle let me know. whatever that will help clarify the circuit/PCB layout. let me know your thoughts pls. How do I troubleshoot the voltage across components. looking forward to hearing from you guys

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