Leviton GFCI nuisance tripping and circuit analysis

[tersh]

Is the arrow in blue the SCR?

The thing is designated "BT169 1702". Is it the SCR? The left pin is connected to pin 7 of the chip (as shown in circuit diagram).

When I shorted it with alligator click (the red curve), the shaded pole motor no longer trips! (after 20 switches). Usually it trips every 4 out of 5 times. So your theory seems to be correct

If it is the SCR. What does shorting the cathode and gate do to the SCR?

You may notice there is a second SCR in the circuit. I think it is to used to control the second solenoid that is use for Reset. In the Leviton teardown. The Reset is done mechanically and there is only one solenoid to open it only.

I'll tear down it to analyze the connections of the second solenoid after the following issue is cleared.

How come when pin 6 was disconnected from the chip. The shaded pole motor inductive kick can still affect the SCR and C3? Where is the path of the current? Can it still pass via the chip even when supply input was gone?

 

[tersh]

You may notice there is a second SCR in the circuit. I think it is to used to control the second solenoid that is use for Reset. In the Leviton teardown. The Reset is done mechanically and there is only one solenoid to open it only.

I'll tear down it to analyze the connections of the second solenoid after the following issue is cleared.

How come when pin 6 was disconnected from the chip. The shaded pole motor inductive kick can still affect the SCR and C3? Where is the path of the current? Can it still pass via the chip even when supply input was gone?

Also here is something not right. Even with pin 6 totally disconnected and my extra GFCI plug in tester connected to soil ground no longer works when 5ma test button pressed. The Test button of the Meiji GFCI outlet still works! I'm suspecting the oem manufacturer cheated by connecting the Test button directly to the 2nd solenoid which opens the contacts even if the sense coil no longer working. Maybe so that they can avoid returns or repair? It's weird because the external GFCI tester with 5mA works. So why don't they make the Test button really genuine? Or with pin 6 removed, could the chip still be working?? Any clue? What next gar? I reviews all about SCR. So shorting the gate and cathode simply make the gate no longer triggerable. But this doesn't prove it's capacitive coupling of the C3 because the chip with pin 6 disabled may still be working partially?

 

[tersh]

You may notice there is a second SCR in the circuit. I think it is to used to control the second solenoid that is use for Reset. In the Leviton teardown. The Reset is done mechanically and there is only one solenoid to open it only.

I'll tear down it to analyze the connections of the second solenoid after the following issue is cleared.

How come when pin 6 was disconnected from the chip. The shaded pole motor inductive kick can still affect the SCR and C3? Where is the path of the current? Can it still pass via the chip even when supply input was gone?

Here I totally cut pin 1, 2, 3 (all sense coil input) of the chip in addition to the pin 6, yet the Test button of the Meiji GFCI still work!

So it's a fake Test button, why would china do this? To prevent return years later? What is your theory? With external GFCI tester, it doesn't work anymore. In new units. The external tester works with 5mA tripping.

With pin 1, 2, 3, and 6 gone. The shaded pole motor still trips 4 out of 5 times. Only when gate and cathode shorted that it doesn't trip. The ultimate test is removing the entire chip. But i'm afraid the gate may no longer be triggered.. I need to know first where exactly does the inductive kick go to C3?

 

[tersh]

Here I totally cut pin 1, 2, 3 (all sense coil input) of the chip in addition to the pin 6, yet the Test button of the Meiji GFCI still work!

So it's a fake Test button, why would china do this? To prevent return years later? What is your theory? With external GFCI tester, it doesn't work anymore. In new units. The external tester works with 5mA tripping.

With pin 1, 2, 3, and 6 gone. The shaded pole motor still trips 4 out of 5 times. Only when gate and cathode shorted that it doesn't trip. The ultimate test is removing the entire chip. But i'm afraid the gate may no longer be triggered.. I need to know first where exactly does the inductive kick go to C3?

I don't like to wait. So I removed Pin 7, 8. It is after they were removed that I could no longer press the Test button and the Shaded pole motor doesn't trip anymore even without shorting the gate and cathode.

To recap:

Pin 7 is the SCR Trigger and Pin 8 is the Delay Cap.

When Pin 7, 8 still connected. The shaded pole motor still tripped 4 out of 5 times (gate & cathode not shorted) and Test button still work (even when pin 1,2,3,6 gone). I'm sure of this because I tested them many times.

Could the inductive kick somehow still able to get into the chip itself, and not because of capacitive coupling in C3? what do you think gar?

Right now. Only Pin 4, 5 still connected. The Ground and Line.

Why is there a separate pin 6 for Supply Input and pin 5 for line?

I still haven't disconnected pin 4,5 in case I have to solder back pin 7 to see if the shaded pole motor would trip again.

 

[junkhound]

Quit trying to use the Fairchild schematic, it is obvious that the insides of that chip and the circuit you keep copying from the USA app note is NOT what you have in the Chinese counterfeit.

Reverse engineer the board at least and draw out the REAL schematic. - e.g. your last pic shows a Q2 in the lower RH corner, no such item in the app note, 2nd solenoid coil, etc, etc.....

Hard to read a Longfellow poem when all you have is a book by Poe?

Interesting thread, but almost surprised the mods don't close it ?

 

[tersh]

I don't like to wait. So I removed Pin 7, 8. It is after they were removed that I could no longer press the Test button and the Shaded pole motor doesn't trip anymore even without shorting the gate and cathode.

To recap:

Pin 7 is the SCR Trigger and Pin 8 is the Delay Cap.

When Pin 7, 8 still connected. The shaded pole motor still tripped 4 out of 5 times (gate & cathode not shorted) and Test button still work (even when pin 1,2,3,6 gone). I'm sure of this because I tested them many times.

Could the inductive kick somehow still able to get into the chip itself, and not because of capacitive coupling in C3? what do you think gar?

Right now. Only Pin 4, 5 still connected. The Ground and Line.

Why is there a separate pin 6 for Supply Input and pin 5 for line?

I still haven't disconnected pin 4,5 in case I have to solder back pin 7 to see if the shaded pole motor would trip again.

I hate loose ends (pun unintended). I tried to reconnect pin 7 (SCR trigger). Somehow the alligator shorted across pin 7 and pin 1, 2 and the chip got fried. This proved that it was still powered with Pin 5 (line) and pin 4 (ground) still around (even without pin 6). And so the following may be concluded.

1. The Test button is fake and can somehow trigger pin 7 without any sense coil input (with pin 1, 2, 3, 6, disconnected). How does it do that? I'm sure of this and not imagining things.

2. The Inductive Kick from shaded pole motor can somehow pass through the chip (with only pin 4,5,7,8 connected) to the SCR Trigger in pin 7 and into C3 causing capacitive coupling as per gar theory? Please tell me gar, without pin 7 SCR Trigger connected, can the SCR be triggered directly? Or does it have to pass through pin 7 SCR Trigger? What do you think? If the SCR can be triggered by inductive kick directly without passing via the chipset and it's not doing it now. Then it may not be C3 but something in the chip causing the trips.

 

[tersh]

Quit trying to use the Fairchild schematic, it is obvious that the insides of that chip and the circuit you keep copying from the USA app note is NOT what you have in the Chinese counterfeit.

Reverse engineer the board at least and draw out the REAL schematic. - e.g. your last pic shows a Q2 in the lower RH corner, no such item in the app note, 2nd solenoid coil, etc, etc.....

Hard to read a Longfellow poem when all you have is a book by Poe?

Interesting thread, but almost surprised the mods don't close it ?

I mentioned earlier that the second Q2 and second solenoid was used for Reset button. In the original Leviton GFCI receptacle, Reset was mechanical and not electronic. This one was electronic. I traced the circuit this morning but the other side was blocked by the solenoids so couldn't see the trace and will do the full trace tomorrow after I removed the solenoids.

Also if you will read the datasheet, you can't change much about the circuit components without changing the tripping current, etc. so it's at least very close. The FM2141 chip and RV4141A is identical they have to be licensed or copied. The datasheet of the two is 100% similar.

I'm an electronic engineer that's why this thread was allowed. I'm not kidding. I took 5 years studying Electronics and Communications Engineering in the 1990s.

 

[gar]

190114-0827 EST

tersh:

You take very good pictures. Sharp and well lighted. Except for some.

In post #98 you cut the pin 6 lead at the IC (Integrated Circuit). Apparently I typed the wrong number for the pin. The pin I wanted cut for the experiment was 7, the pin that goes to the gate of the SCR. I have a really major problem with my keyboard and adjacent keys being output when I hit a particular key.

So I want pin 7 disconnected at the IC. With that done then there would be no signal from the IC to the SCR.

With pin 7 disconnected from the circuit board trace at the IC, and with the short from gate to cathode removed, do we get false triggering?

When pin 7 is disconnected from the PC board you should not be concerned with anything the IC is doing. If we get false triggering, then try putting a 10 nf capacitor where you had the shorting wire, and see if there is a change in the probability of false triggering. The leads from the capacitor to the gate and cathode should be as short as possible.

.

 

[tersh]

190114-0827 EST

tersh:

You take very good pictures. Sharp and well lighted. Except for some.

In post #98 you cut the pin 6 lead at the IC (Integrated Circuit). Apparently I typed the wrong number for the pin. The pin I wanted cut for the experiment was 7, the pin that goes to the gate of the SCR. I have a really major problem with my keyboard and adjacent keys being output when I hit a particular key.

So I want pin 7 disconnected at the IC. With that done then there would be no signal from the IC to the SCR.

With pin 7 disconnected from the circuit board trace at the IC, and with the short from gate to cathode removed, do we get false triggering?

When pin 7 is disconnected from the PC board you should not be concerned with anything the IC is doing. If we get false triggering, then try putting a 10 nf capacitor where you had the shorting wire, and see if there is a change in the probability of false triggering. The leads from the capacitor to the gate and cathode should be as short as possible.

.

Funny. Mistyping pin no. But if you would see my last messages where I removed each. It was only when I removed pin 7 and 8 that the motor stopped tripping. This with the short from gate to cathode removed.

But with pin 7 still connected. The motor no longer tripped when gate and cathode shorted.

So what do you think is the cause of the inductive kick? Without the chip installed, can the gate still be triggered? from where?

 

[tersh]

Funny. Mistyping pin no. But if you would see my last messages where I removed each. It was only when I removed pin 7 and 8 that the motor stopped tripping. This with the short from gate to cathode removed.

But with pin 7 still connected. The motor no longer tripped when gate and cathode shorted.

So what do you think is the cause of the inductive kick? Without the chip installed, can the gate still be triggered? from where?

Here is the summary.

With pin 6 removed, there is still shaded pole motor triggering.
But when gate and cathode shorted, no more tripping.
When pin 1,2,3 (or sense coil input) disconnected. There is still tripping when gate and cathode not shorted.
When pin 7,8 removed. That's when the motor stopped tripping without shorted gate and cathode.

Lastly, the last pin 4,5 was removed and the chip removed.

So what is your conclusion? (please read the last message above too).

 

[tersh]

Here is the summary.

With pin 6 removed, there is still shaded pole motor triggering.
But when gate and cathode shorted, no more tripping.
When pin 1,2,3 (or sense coil input) disconnected. There is still tripping when gate and cathode not shorted.
When pin 7,8 removed. That's when the motor stopped tripping without shorted gate and cathode.

Lastly, the last pin 4,5 was removed and the chip removed.

So what is your conclusion? (please read the last message above too).

My conclusion of the above observations was that the inductive kick passes through pin 4 (line), pin 5 (ground). And inside the chip it somehow cause the pin 7 (SCR Trigger) to be get turned on triggering the gate.

 

[gar]

190114-1043 EST

tersh:

I don't have time now. Tonight I will try to study what you have done.

.

 

[gar]

190114-2002 EST

tesch:

My mistyping of 6 instead of 7 is a real problem in this experiment. But based upon what I was describing the experiment was to do you should have caught the mistake and questioned if the pin number was correct. But we are where we are now.

So in the present state of the board, meaning no IC, and if you remove the gate cathode short, then does the device falsely trip?

When you first opened pin 6, power to the IC, there was no power to the chip, and thus, it should not have been functional.
In the unpowered state the IC might have been some form of capacitor or conductor that coupled to the SCR gate, but it was not an active device doing its normal function.

Another problem is your schematic does not correspond with the actual circuit, possibly two SCRs and not just one.

.

 

[tersh]

190114-2002 EST

tesch:

My mistyping of 6 instead of 7 is a real problem in this experiment. But based upon what I was describing the experiment was to do you should have caught the mistake and questioned if the pin number was correct. But we are where we are now.

So in the present state of the board, meaning no IC, and if you remove the gate cathode short, then does the device falsely trip?

When SCR Trigger in Pin 7 was removed or the entire chip, there is no more false triggering even if there is no short between gate and cathode.

When you first opened pin 6, power to the IC, there was no power to the chip, and thus, it should not have been functional.
In the unpowered state the IC might have been some form of capacitor or conductor that coupled to the SCR gate, but it was not an active device doing its normal function.

When pin 6 was removed, it can still trip. Only when pin 7 or SCR trigger removed that tripping stopped. So even with no input supply, the capacitor or conductor inside still working somehow. But pin 5 is line, what is the difference between pin 5 and pin 6? see:

Another problem is your schematic does not correspond with the actual circuit, possibly two SCRs and not just one.

.

I just finished tracing every components in the circuit. 1/4 of the circuit is related to electronic reset. In the US. When you press Test, the Reset button comes up, it is because it is mechanical. But with the china clone. It is electronic, the Reset button doesn't come up when Test is pressed. This is how the second solenoid work:

How it works is when Reset was pressed. The contacts come to the top (attracted by the top solenoid). And in the second solenoid, there is a pin with spring that locks the contacts (in top position) into place. When the SCR and main solenoid (the right horizontal one) triggers, it pulled the pin to the right magnetized metal hence the contacts come down (with spring inside). This is an ingenious electronic reset design, what GFCI in the US use it?


Later I'll put the actual values of other components in the circuit which I have fully traced. But I just want to know something for now. Pin 4 is Ground. But actual inputted voltage is 240v line to line, the Pin 4 ground is connected to one of the input 240v lines, do you think it can affect the chip? I still am figuring out why even with pin 1,2,3 removed, the Test button still work. In the actual circuit. It is really connected between outside and inside (or other side) of sense coil with 24k instead of 15k connected. I'm still perflexed why the test button still work even without the sense coil input in pin 1,2,3.

 

[tersh]

When SCR Trigger in Pin 7 was removed or the entire chip, there is no more false triggering even if there is no short between gate and cathode.



When pin 6 was removed, it can still trip. Only when pin 7 or SCR trigger removed that tripping stopped. So even with no input supply, the capacitor or conductor inside still working somehow. But pin 5 is line, what is the difference between pin 5 and pin 6? see:

I just finished tracing every components in the circuit. 1/4 of the circuit is related to electronic reset. In the US. When you press Test, the Reset button comes up, it is because it is mechanical. But with the china clone. It is electronic, the Reset button doesn't come up when Test is pressed. This is how the second solenoid work:

How it works is when Reset was pressed. The contacts come to the top (attracted by the top solenoid). And in the second solenoid, there is a pin with spring that locks the contacts (in top position) into place. When the SCR and main solenoid (the right horizontal one) triggers, it pulled the pin to the right magnetized metal hence the contacts come down (with spring inside). This is an ingenious electronic reset design, what GFCI in the US use it?


Later I'll put the actual values of other components in the circuit which I have fully traced. But I just want to know something for now. Pin 4 is Ground. But actual inputted voltage is 240v line to line, the Pin 4 ground is connected to one of the input 240v lines, do you think it can affect the chip? I still am figuring out why even with pin 1,2,3 removed, the Test button still work. In the actual circuit. It is really connected between outside and inside (or other side) of sense coil with 24k instead of 15k connected. I'm still perflexed why the test button still work even without the sense coil input in pin 1,2,3.

As I have fully traced the circuit, the following shown in red slant mark and arrows is the electronics of the Reset SCR switch and Reset Solenoid wire pins only. In the US, your GFCI reset is mechanical, so these electronics don't exist. These are in addition to the Fairchild circuit diagram. Let's just focus on the main circuit diagram from on.

 

[gar]

190114-2133 EST

tersh:

Pin 4 labeled GND has nothing to do with earth or neutral. It would be better to call it common. It is the electronic common reference.

Pin 6, Vs, is not power input. Pin 5, line, is power input from the 1N4004 diode. It appears that pin 6 is a place to connect a capacitor to filter the pulsed DC from the diode.

Pin 7 is the trigger to the SCR.

Pin 8 is apparently a place to connect a capacitor to control the inverse time function.

Pins 1, 2, and 3 are the signal inputs.

From measurements you are now providing it appears the false tripping comes from pin 7. This conclusion is based on your circuit in its present state that as I understand consists of C3, a trace from C3 to the SCR gate, and the SCR connected to its trip coil.

.

 

[tersh]

190114-2133 EST

tersh:

Pin 4 labeled GND has nothing to do with earth or neutral. It would be better to call it common. It is the electronic common reference.

Pin 6, Vs, is not power input. Pin 5, line, is power input from the 1N4004 diode. It appears that pin 6 is a place to connect a capacitor to filter the pulsed DC from the diode.

Pin 7 is the trigger to the SCR.

Pin 8 is apparently a place to connect a capacitor to control the inverse time function.

Pins 1, 2, and 3 are the signal inputs.

From measurements you are now providing it appears the false tripping comes from pin 7. This conclusion is based on your circuit in its present state that as I understand consists of C3, a trace from C3 to the SCR gate, and the SCR connected to its trip coil.

.

The following are the changes in the actual circuit compared to the chip datasheet:

The red are the changes in the values of the resistors and capacitors. Also they reversed the position of Rline to the diode. They added another diode before the solenoid (shown in red).

I'm spending time on this because it is the only 240v GFCI with 5mA tripping the whole world and I'd be stuck with the model (and millions of my countrymen and all other 240v users worldwide (the model is distributed in Italy too under Lumex)) probably for the rest of my life. And it's not just a toy circuit but one that involves a matter of life and death (GFCI prevents electrocution).

That said. Something perflexed me so much. When I disconnected pin 1,2,3 and all sense coil input gone. The test button still works sporatically (sometimes only, sometimes not). It's as if the test button can mimic inductive load itself? What if I get another new GFCI unit and disconnect pin 1,2,3 totally and the test button still work. What can you conclude? Based on trace, it is connected right with 24k instead of 15k to produce 240/24k = 10mA.

 

[gar]

190114-2245 EST

tersh:

The diode below the solenoid makes no sense unless it is a Zener diode. Note the polarity.

The resistor in series with the 1N4004 is larger. Probably because of the higher supply voltage. The moved location may have been to try to reduce false triggering. This might imply that false trigger may come thru this power supply lead.

The test button false triggering when 1, 2, and 3 are opened makes no sense.

This device may have a higher threshold current level than 5 mA.

.

 

[tersh]

190114-2245 EST

tersh:

The diode below the solenoid makes no sense unless it is a Zener diode. Note the polarity.

The resistor in series with the 1N4004 is larger. Probably because of the higher supply voltage. The moved location may have been to try to reduce false triggering. This might imply that false trigger may come thru this power supply lead.

The test button false triggering when 1, 2, and 3 are opened makes no sense.

This device may have a higher threshold current level than 5 mA.

.

I traced it carefully now. I spent a while tracing the Reset electronics so missed it. This is the actual connection of the extra diode.

The question mark is a thermal fuse (i just found out) http://www.setfuse.com/product/over.../thermal-cutofftco/radial-shape/f-series.html why did they put diode on it?

This is the actual circuit trace:

About the pin 1, 2, 3 disconnected and the Test button still work randomly. It's really true. I spent long with this testing. It's not always, you have to press it repeatedly then it trips. Maybe it can induce transient?

 

[gar]

190114-2427 EDT

tersh:

As redrawn the diode near the trip coil makes perfect sense. And it will keep the trip coil energized longer.

I have no idea why the ??? thing would be needed.

.