Electric blanket

Thread Starter

Ravi_UiA

Joined Mar 22, 2020
8
Hi!
I have an electric planket that stopped working and it is showing "E" on the 7-segment display.
I had checked the voltages on different points, all were as it should be except the opto-coupler ( that i replaced with new one). It still shows "E" and not working. Please see the attached schematic, I appreciate all contributions.
 

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drc_567

Joined Dec 29, 2008
1,062
... Another check ... Is there a closed circuit across the two leads going directly into the blanket?
Maybe folding or wear has caused a break in the actual blanket heating wires.
 

Thread Starter

Ravi_UiA

Joined Mar 22, 2020
8
... Another check ... Is there a closed circuit across the two leads going directly into the blanket?
Maybe folding or wear has caused a break in the actual blanket heating wires.
It can be! I have tested the controller of the blanket without connecting the blanket. I have used the multimeter to chech if there is a short but i could not find any.
 

drc_567

Joined Dec 29, 2008
1,062
... please clarify ... There should be a reasonable resistance, some finite number, when the resistance of the blanket leads is measured.
 

Thread Starter

Ravi_UiA

Joined Mar 22, 2020
8
... please clarify ... There should be a reasonable resistance, some finite number, when the resistance of the blanket leads is measured.
I could not measure any resistance between the hot line and gnd (or between H2Red and hotline and gnd) on the blanket. it means there is infinte resistance?
 

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drc_567

Joined Dec 29, 2008
1,062
Can you measure the voltage on the controller between the H2Red lead and ground?
... Be Careful, because the adjacent component on the controller board is a triac, which means that 230 volts AC is present and requires attention to safety. If you measure an AC voltage between H2red and neutral, then it is likely that the problem is a continuity break someplace in the blanket.
...edit ... It looks like the blanket needs to be plugged in to check the triac voltage.
 
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Thread Starter

Ravi_UiA

Joined Mar 22, 2020
8
Can you measure the voltage on the controller between the H2Red lead and ground?
... Be Careful, because the adjacent component on the controller board is a triac, which means that 230 volts AC is present and requires attention to safety. If you measure an AC voltage between H2red and neutral, then it is likely that the problem is a continuity break someplace in the blanket.
...edit ... It looks like the blanket needs to be plugged in to check the triac voltage.
It shows ZERO voltage. but what is the function of H2red? the hotline is connected to blanket.
 

drc_567

Joined Dec 29, 2008
1,062
... If there is no AC voltage at H2red, that seems to indicate a fault or problem of some sort between the 230 volt supply at the wall and its connection to the controller. This might be a broken wire someplace. If you had an identical good blanket you could plug it into the control board and verify this.The other possibility is that there is something wrong with the triac trigger voltage, but that would require an oscilloscope to observe and check.
... Just an opinion at this point, but it seems more likely that the problem is something wrong with the blanket.
 

Thread Starter

Ravi_UiA

Joined Mar 22, 2020
8
... If there is no AC voltage at H2red, that seems to indicate a fault or problem of some sort between the 230 volt supply at the wall and its connection to the controller. This might be a broken wire someplace. If you had an identical good blanket you could plug it into the control board and verify this.The other possibility is that there is something wrong with the triac trigger voltage, but that would require an oscilloscope to observe and check.
... Just an opinion at this point, but it seems more likely that the problem is something wrong with the blanket.
I have an oscilloscope, but the problem is i don't know what to measure on the trisac. I have never worked with such thing, i tried to read the datasheet but it is difficult to sort out. Could you please give me a hint on how the moc3041 BTA06-600c works? or what to measure?
 

drc_567

Joined Dec 29, 2008
1,062
A triac conducts a portion of the AC waveform that goes through the load to ground. That fraction of on time is controlled or adjusted by the gate trigger. With the power off, just to be sure, you might check the triac to see if it is shorted out. There should be no conductivity through it. However, if you do not measure any AC voltage at the H2red terminal, with the blanket plugged into the wall, then something is wrong with the connection between the 230 volt wall connection and the H2red terminal. The place to look for a broken wire would be either at the wall plug connector or else at the blanket connector. Finding the broken wire would involve examining the blanket wiring near each connector, and would be a difficult task, exposing the wires. If you can determine which one of the blanket connector jacks is for the 230 volts, then check continuity between the wall plug hot wire and the H2red connector AC voltage jack. There should be continuity between the two.
... Do not try to measure the AC voltage with your oscilloscope. Doing so can result in a dangerous situation. It is possible to damage your oscilloscope if you place the scope ground connector in the wrong place.
... edit ... There is also a wire connecting the wall plug neutral and the controller board. If possible, check to see that there is continuity between these two points ... That is, the ground/neutral wire is not broken at some point.
 
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