Here is what I did

 

Ok, so I soldered in a diode on the positive leg coming from the 9 volt bat, got rid of the potentiometer, and still tested the same. So I guess the feedback network is not working?

 

U2 pin numbers are not correct (red numbers you added).
1,2,3 are correct but pin 4 should be opposite pin 3.
Interchange 4 and 6.

Timescope

 

On which pic? Top of board or the underside where U2 is mounted?

 

Sorry Timescope, I drew the pics incorrectly. Yes pin 4 and 6 should be switched. That is how I tested. I just had it backwards when I drew that in paint program. Pin 5 goes to pin 1 on U3. So sense I tested it correctly, where does that leave me?

 

Hi diebog,
I just calculated the voltage that the TL431 switches the opto on using the values for R19, R20 and the typical Vref of the TL431:

V = Vref (1 + 5.49/1.78) = 2.495 x 4.08 = 10.19 volts.

So the 9v battery is inadequate.

I edited my previous post and attached the pin connections of the opto.

1. Connect the diode test meter to pins 4 and 5.

2. Replace the diode you connected to the battery with a 1kΩ resistor.

3. Connect the negative terminal of the battery to pin 2 of U2 (MOC8102)

4. Connect the 1kΩ resistor to pin 1 of U2.

5. The diode test meter should show continuity between pins 4 and 5.

Timescope

 

Ok, I'll try that tomorrow. Question about the voltage, if 10.19 volts is what's needed, what does adding a 1kohm resistor do or change vs the diode? What raises the voltage to 10.19 to test it correctly? Or am I to use a 12v battery?

 

The 1k resistor limits the current through the led in the optocoupler while we are testing it.

The diode was intended to reduce the 9v to about 8.4v.

What kind of 12v battery ?

Timescope

 

I have some auto 12v battery's, I have 12vdc 1amp trickle charger, I have 18v lithium battery's from my Makita cordless drills. I have a bunch of dc wall plug transformers, I can check for a optimum voltage range if that helps.

 

Let's test the optocoupler with the 9v battery and 1k resistor first.

Timescope

 

Ok, I'll do that tomorrow and report back. Thanks again for helping me

 

Have a good day (or night).

Timescope

 

Just did the test, here is what I got

one tester I had .600 mv and when battery is connected it goes down to .143 mv
second tester .985mv down to .147 mv

So does 1.47= continuity? I thought it would show OL or 000 if there was continuity


I found an 1kΩ resistor on an scrap board I had brown,black,red,gold which should be a 1kΩ resistor. I checked with meeter to confirm and it was correct.

 

Have a good day (or night).

Timescope

Im in California, where about are you?

 

If you connected the +ve probe of the meter to pin 5 of U2 and the -ve probe to pin 4, then something is wrong : either U2 or U3 is defective.

Remove U3, UCC2804 from the circuit and test the optocoupler again.

How you remove it will depend on the soldering equipment at your disposal. Care must be taken to avoid lifting the pcb traces.

I'm in Freetown, Sierra Leone, West Africa, about eight or nine hours ahead of your time.

Timescope

 

What is the best way to remove it? I have a digital 80 watt solder station with a fine point and also a bunt point tip. I have a few other cheaper irons and a desolder iron with a bulb that sucks up solder.

 

I usually apply solder to all the pins on one side of the ic, then try to lift that side of the ic up with a small precision screwdriver while heating all the pins simultaneously. You have to do it quickly to avoid overheating the ic.

Use the blunt tip.

Timescope

 

Ok, ill try that. Sense I have a replacement is it that big of a deal if I over heat it?

 

You may also overheat the circuit board as well, lifting the traces.

Timescope

 

Ok did what you said and it came off real easy. Traces didnt lift and didn't overheat u3. I redid the test and now there is continuity all the time with out the battery connected.