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John

On 20 Oct 2006 08:51:43 -0700, wrote:

Hi, I am new to this so any help would be appreciated. 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...

thanks

Humidity sensors are difficult to check, as the sensor element is
often a capcitive device that is driven by an AC voltage which is
generated on the controller board. Without an oscilloscope to check
for the AC waveform and/or a service document that specifies the
expected voltages, this is hard to test.