MSefi.com read only forum (Jan.15,2018)

I am assembling a megaquirt II Version 3.0 Board code version v2.920.abs.s19. I hooked my board to a Stim and I am able to see the feedback for the TPS, Coolant Temp, Intake Air Temp, and if I make an adjustment and cycle power I see a EGO change also. I am not getting anything on my tach. I have XG1 and XG2, Tachselect and Optoin, and Tsel and Optoout Jumpered. I also have a zener installed and jumped out at D2. I can see a square wave pulse on my Oscope around 5.1 volts which seems to respond correctly with the 2 pot adjusters. If I remember correctly I had the span set to roughly 2ms to see the pulse. I can see the pulse on both sides of D1 and the jumpered D2. I also see it on one side of R12. On the other side of R12 the voltage drops to roughly 1.26 volts (as I expect), but the square wave doesn’t look nearly as nice and my Oscope no longer recognizes it as a duty cycle, but there is still a rough signal that reacts to me adjusting the pots. I see this voltage (1.26V) at pin one of the opto-isolator( which from the data sheet 1.3V is typical). (I also see ground at pin 2 and pin 6. What type of voltages should I expect on the opto-isolator pins and how can I test if it is actually firing. Thanks Mark

This is a test I wrote for testing with just a volt meter:

With the Megasquirt powered up, apply 12 volts to pin 24 or TachSelect, and check the voltage on the TSEL jumper with a voltmeter. You should read zero volts. Next, ground pin 24 so it has no volts on the input circuit, and check TSEL's voltage again. You should see 5 volts there. Let me know what you find.

It could also be adapted to an oscilloscope with the same rules: 0 volts on the output when the input is energized, 5 volts when the input is grounded.

I appreciate your help. I haven't had internet access for several days. I traced the problem to my stim timing circuit. I actually did some more searching and came across a reply you gave for testing the op-amp and found mine to check out ok. I then hooked it up to my truck and got a tach signal. All is good. again Thank you.

You're welcome.