Any equivalent with the same Zener voltage and current should do, it not that critical.
There is also a 1N4007 or equiv. in series with it.

 

Any equivalent with the same Zener voltage and current should do, it not that critical.
There is also a 1N4007 or equiv. in series with it.

I checked the 1n4007 and it measures fine. When I check the zener out of circuit I get nothing at all on the dmm. I have some zy12 zeners but they don't have exactly the same characteristics as the 1n4744a that I removed. I am unsure how critical the values are. the zy12 has a lower voltage and higher current ratings.

 

I should be OK to try, it's other use is to supply U4 trigger diode for the ramp up voltage.
You should at least get the 5v for the micro.

 

I should be OK to try, it's other use is to supply U4 trigger diode for the ramp up voltage.
You should at least get the 5v for the micro.

replaced D8 with my 2m12z zener and still don't measure voltage on the pins 10 and 20 of the micro or on RG1. I am testing voltage with the positive probe on the test point and the negative probe on the heat sink, is it okay to be doing it that way?

I really appreciate your help by the way, I am learning a lot from this, thank you

 

First you need the input voltage to RG1, if zero, then work back from there.

 

I have gone through the board and tested the diodes which seem fine, the rectifier is fine, I do not have an esr tester so cannot test the caps. The circuit diagram I am using may be incorrect because 8 different resistors have different values than on the diagram. I have the MC2100WAM revision 37376. I have tried to find the different mc2100 diagrams on here and can't seem to find them. Here is a picture of my board.

 

Are the voltages now OK at the input of RG1 and the output of the bridge?
I find it easier to solder a short insulated conductor at the -ve foil output of the bridge and use a croc clip meter lead so it leaves one hand free to take all the necessary readings ., just scrape or clean off the coating on the foil.
Is the ceramic resistor getting warm/hot?