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

I am in the process of building a MS for the first time. I built my jimstim and plugged it in to perform an op-test of the pcb power circuit. I receive ALL voltages where they need to be, but I am getting 5V on pins 19 and 2 of U1 (CPU). According to sheet 1 of the schematic (Megasquirt-CPU,Rev 2.991) both should be grounded directly with only a cap (C1) connected to power. I checked the cap and it tests fine. Also pin 32 should be directly grounded per the drawing but no dice. There is no direct short to ground that I can find from the power circuit.

Is there a change to this drawing or did I screw up my pcb build?

My guess is you didn't let the solder flow properly when installing the 32 pin socket. Or were using too thick a solder so not enough flux. Are other joints like resistors showing a good flow on both sides of the board? And are you using lead solder?

I am using .32 lead free solder. I am a veteran Navy certified electrician and have been soldering for a long time. My terminals look like the pictures in the Navy manual. I have continuity tested alot of points on the pcb with my DMM and have .03 ohms restistance. I will however try and reflow the points on U1 when I get home.

I'm pretty sure that poor solder points aren't going to generate 5V though.

I'm surprised you're using lead free if ex-navy - it's my understanding the military won't allow it anywhere.

I based my comment on the ground connections being IIRC on an inner layer of the PCB, so most likely not making a connection due to a soldering problem. If the ground plane is at 5 volts the same applies - but elsewhere. Where were you picking up your DVM ground?

Actually I found an ID-10t error. It helps if you ID the right pin as #1. Lower right not lower left. No problems.

As far as lead free solder- I am building this thing on my kitchen table and my kids like to observe and touch everything; better safe than sorry.

Thanks for the input guys!!