Testing a Dehumidifier circuit
 

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

Testing a Dehumidifier circuit
 

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.

Testing a Dehumidifier circuit
 

This board has no humidity sensor. that is external and a mechanical
one. what this board does or is suppose to do when you turn the knob on
humidistat this waits for a couple of mins and then relay clicks and
the dehumidifier starts. this doesnt click at all. I moved the relay to
another board and tested and that is good. any other reference material
or site/forum to get additional help would be appreciated.



John wrote:
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.

Testing a Dehumidifier circuit
 

wrote in message
ups.com...

This board has no humidity sensor. that is external and a mechanical
one. what this board does or is suppose to do when you turn the knob on
humidistat this waits for a couple of mins and then relay clicks and
the dehumidifier starts. this doesnt click at all. I moved the relay to
another board and tested and that is good. any other reference material
or site/forum to get additional help would be appreciated.

Then it is a time delay, designed to prevent quick restart of the
compressor. You need a circuit diagram, service manual or several years of
experience to repair it.

Testing a Dehumidifier circuit
 

Homer J Simpson wrote:
wrote in message
ups.com...

This board has no humidity sensor. that is external and a mechanical
one. what this board does or is suppose to do when you turn the knob on
humidistat this waits for a couple of mins and then relay clicks and
the dehumidifier starts. this doesnt click at all. I moved the relay to
another board and tested and that is good. any other reference material
or site/forum to get additional help would be appreciated.

Then it is a time delay, designed to prevent quick restart of the
compressor. You need a circuit diagram, service manual or several years of
experience to repair it.

Yes, or if youre lucky posting the cct diag for us to see might get you
somewhere. No circuit, forget it.


NT

Testing a Dehumidifier circuit
 

Homer J Simpson wrote:

Then it is a time delay, designed to prevent quick restart of the
compressor. You need a circuit diagram, service manual or several years of
experience to repair it.

Yes, or if youre lucky posting the cct diag for us to see might get you
somewhere. No circuit, forget it.

Forgot to mention, if its a time delay you could likely run the system
without it, if necessary.


NT

Testing a Dehumidifier circuit
 

wrote in message
ps.com...

Forgot to mention, if its a time delay you could likely run the system
without it, if necessary.

If you replace it with a manual switch and don't quickly restart the
compressor. But even then there may be an anti freeze or overflow switch.

Testing a Dehumidifier circuit
 

There is an IC on the board which I believe has the time delay. Should
I try replacing that ? I did a manual test and gave a little voltage
across emitter and base and the relay clicked, so the transistor is ok.
I can post the PCB picture if you guys think will help, let me know
pls.


Homer J Simpson wrote:
wrote in message
ps.com...

Forgot to mention, if its a time delay you could likely run the system
without it, if necessary.

If you replace it with a manual switch and don't quickly restart the
compressor. But even then there may be an anti freeze or overflow switch.

Testing a Dehumidifier circuit
 

wrote in message
oups.com...

There is an IC on the board which I believe has the time delay. Should
I try replacing that ? I did a manual test and gave a little voltage
across emitter and base and the relay clicked, so the transistor is ok.
I can post the PCB picture if you guys think will help, let me know
pls.

How much experience have you with appliances and AC powered equipment?

Testing a Dehumidifier circuit
 

Testing a Dehumidifier circuit
 

Testing a Dehumidifier circuit
 

checked that the IC pin1 and pin8 should be getting 5v DC. its getting
about 0.3v so the timer is not kicking in which in result doesnt start
the relay through transistor. i have checked Diodes they conduct one
way, also checked all resistors and one 47uF 65v capacitor. There are
two small capacitors 0.1uF I believe which doesnt show me any signal.
maybe too small to be tested ? How do I check the transistor, Its C556B
PNP I believe. It looks to be ok because when I gave a small voltage
across two pins on the transistor the relay contacted.


On Oct 26, 4:33 am, wrote:
wrote:
There is an IC on the board which I believe has the time delay. Should
I try replacing that ?no

Testing a Dehumidifier circuit
 

Testing a Dehumidifier circuit
 

I will try and create a circuit diagram by hand for this board, its a
small board so someone here can give me idea what failed thats stopping
from giving 5v across the timer IC.


James Sweet wrote:
wrote:
checked that the IC pin1 and pin8 should be getting 5v DC. its getting
about 0.3v so the timer is not kicking in which in result doesnt start
the relay through transistor. i have checked Diodes they conduct one
way, also checked all resistors and one 47uF 65v capacitor. There are
two small capacitors 0.1uF I believe which doesnt show me any signal.
maybe too small to be tested ? How do I check the transistor, Its C556B
PNP I believe. It looks to be ok because when I gave a small voltage
across two pins on the transistor the relay contacted.



What does the 5V come from? Something may be shorted across it holding
it down, or the power supply may have failed.