OK, The voltage that powers the chip enters on pin 2 and 3. If everything was working you would read about 15 volts DC across pins 2 and 3. You measured 1.6 volts DC, in an earlier post. So, why is this the case?? Either the circuit that supplies the chip with operating voltage is bad, or the chip is bad and is drawing a lot of current, keeping the voltage low. You measured 69 volts across the 6500 resistor, which implies the chip is drawing 0.010 amp. So, it does not appear that the chip is drawing excess current. You measured .8 Vac across 2 and 3, so the two 22uf caps are not open.

Hmmmmm......

Using the "diode" setting, measure both directions, of the SMD diode.

 

Yes I did that in an earlier post. Going from pin 3 towards the resistor (forward biased-red lead on IC side), i have 0.548V. In the opposite direction (reverse biased-black lead on IC side) going to the pin, I have O.L.
Is it possible that pin 2 or 3 is being pulled down somewhere else?
If 69 volts is dropped on the resistor, why am I not measuring 51 volts at the pin? Is it because the diode stops half the wave? Sorry just trying to grasp this concept.

 

You need to get a new IC.

 

You need to get a new IC.

Yes, I have to agree at this point. You may even find a replacement module for not too much more.

Anyone else have any ideas??

 

I agree with your assessment. I wish i knew more of why I agree but that will come. Now I went to FindChips.com and everybody says this chip is obsolete. What a lesson in futility. any ideas?

 

Ebay

They may be obsolete but there are a lot of them still around. U211B2

 

Who do you trust on Ebay? I was on there and you can find that chip from $1.99-$72.00. If I order from Ebay, I need to get it fairly quick as well. Before Christmas would be nice

 

Who do you trust on Ebay?........

Good question. You probably will not get it by Christmas from China, but you will get it eventually or EBay gives you your money back. Look at the "sellers Information" for the percentage of positive feedback. Read some of the positive and negative feedback.

 

You can get from Aliexpress but not so soon, as Christmas is just at the corner.
Find a seller near you from Ebay. It will be better.
Buy around a 5pc lot. A rule I always use is never buy 1pc if you can get 5 or 10pc with a few bucks added. Saves time and money if the one pc you buy is bad. Not that I am saying it will be but who knows.
Ask the seller to sell brand new parts not soldered or used.

We assume the IC fault cause the voltages measured is rather low. The IC is drawing more current due to the fault. The series resistors are of high value and due to this high current , voltage drop is more. Decreasing the voltage required by the IC.
A blown cap could be due to a voltage spike and if this is the case the IC is likely to develop a fault. I hope the triac you replaced is good.

 

Thank you R!f@@. Your explanation is good and I hear what you say about ordering more than one at a time. I usually do that in case one is bad or I make one go bad. The one thing I still don't understand is why the mains are backwards to my diagram and which way current is moving between the chip and the mains. I'm a little fuzzy on the voltage readings I get and perhaps it's because I work with DC all day and not AC. Thanks for all your help

 

The complication of this type of circuit is tht it requires both AC and DC to work.
The DC is not pure DC. I am saying this cause diagram shows just a half wave rectifier and the ACV is used for zero crossing detection and RPM sensing and all tht.

Quite complicated concept is used here....well atleast to me u know

 

Yes I checked it and found three different readings which kind of threw me off. I was looking for a fixed resistance between two pins and found that all three readings were variable between 0.2 - 33,000 ohms roughly.

I would have taken a much different approach to troubleshooting this. Have you read the detailed operation of the control IC in the PDF? It give kind of a step by step of what the IC does and what the external signals need to do.

The first thing I'd check is the speed pot, since it is the only thing that is externally adjustable/moving. Is the resistance varying between it's input and the wiper? Carefully with the router plugged in, is the correct voltage getting to the pots input terminal? By carefully jumpering the pot input terminal to the wiper out put does the motor work? Then I'd check to see that all the correct voltages, as called out in the chip details are there on each pin.

 

I would have taken a much different approach to troubleshooting this. Have you read the detailed operation of the control IC in the PDF? It give kind of a step by step of what the IC does and what the external signals need to do.

The first thing I'd check is the speed pot, since it is the only thing that is externally adjustable/moving. Is the resistance varying between it's input and the wiper? Carefully with the router plugged in, is the correct voltage getting to the pots input terminal? By carefully jumpering the pot input terminal to the wiper out put does the motor work? Then I'd check to see that all the correct voltages, as called out in the chip details are there on each pin.

Much different take on this situation. I did read thePDF from top to bottom. Some of it registered with me and some spoke like Japanese. My electronics skills grow daily but are still at a much lower level than the language spoke on that page. I can follow what you guys tell me to do and I recognize some parts of the circuit for what they do, but I still have a hard time visualizing how all the parts come together to make things work. That is why early in the thread, I asked somebody to break it down in laymans terms. That didn't happen but I can follow the bouncing balls you guys throw at me and do the tests you ask me to do and my hope is that in the end, the motor will work and so will the speed control.
Problem now is that the guy who owns it won't want to wait for IC or whatever parts are needed and I am probably going to end up bypassing the speed control and make it a one speed router. I will try the potentiometer but I think he is at the end of his rope. I can do this all day.

 

I'm back with my router issue and have just finished replacing the U211B phase converter. Transplant went well but now I am presented with a new issue. I now have the motor turning on with the switch which I did not have before, but the router works for about five seconds and then cuts out(quits). I can leave the switch on and nothing else happens. If I shut the switch off and turn it right back on again, the motor will work for another five seconds and then quit. At this rate, I will have routered one piece of wood in about ten days. Any ideas on where to go from here. I don't have the heat shield on the TRIAC. Will it shut down that quickly without it?

 

The triac might even blow without the heat sink. Never run the motor without the sink. I think you are lucky the triac did not short out.
But then again it might have developed a fault with heat. If the problem is there replace triac and run with the heat shield

 

It is kind of a pain to attach the heat shield for testing. Can I get away with a couple of alligator clips as heat sinks. The actual heat shield is riveted to the TRIAC once it is in place permanently.

 

The triac might even blow without the heat sink. Never run the motor without the sink. I think you are lucky the triac did not short out.
But then again it might have developed a fault with heat. If the problem is there replace triac and run with the heat shield

If its going to "blow" - a heatsink won't make much difference.

Without a heatsink; it will get too hot - up to a point, this will just make the gate more sensitive, after that point; the gate becomes a permanent one-shot.

 

I suggest that you put it back with the sink and test.

 

I will do that tonight or tomorrow and post back the results I will also try to track down where the voltage is staying and where it is not.

 

I put the heat shield back on and here is the results. When I turn it on, 5 seconds and then it shuts off. I measured the voltage at the three pins on the TRIAC. A2 and G (the center pin and right side pin) go to 120 VAC and then remain there after it shuts off. The left side pin A1, drops down to 0 VAC and the motor dies. If I leave it turned on, nothing happens. If I shut it off and reapply power, away it goes for another five seconds. Datasheet attached.