JimStim v1.5 No Tach Signal

[mattrabbit]

I just finished assembling my JimStim v1.5 from DIYAutotune and I don't seem to get any tach signal. None of the components are heating up and I just wanted to see if there is any way to tell if I just got a DOA chip or what. All of the LEDs are working fine and all of my solder joints are solid.

[jbelanger]

Have you performed the tach signal test described here: http://jbperf.com/JimStim/JimStim_v1_4_ ... ml#testing? And make sure you have 3.3V at pins 1 and 3 of the JimStim CPU.

You also have to make sure you have all the needed jumpers for the tach circuit you're using on your MS. See here: http://jbperf.com/JimStim/JimStim_v2_0_ ... .html#tach

Jean

[mattrabbit]

I just checked and I have 3.3V at pin 1 and 3 of the cpu socket. I haven't built the megasquirt yet, so that tach signal test is the only thing I can do right now and it doesn't show any signal.

[jbelanger]

Check the voltage at each pin of the CPU with and without the CPU in place and post the values here.

Jean

[mattrabbit]

Got it figured out, It was the power source.

Thanks for the help.

[jbelanger]

The 5V pins will not have any voltage until you connect the MS because that's where this voltage is coming from.

The voltage you're seeing means there is something wrong. You mentioned that nothing was heating up but can you re-check F1, U2, D4 and the CPU. By the way, is this with or without the CPU? Check with both and if there is a difference, the CPU is the likely culprit. If it doesn't make a difference, then one of the other components listed will heat up.

Jean

[mattrabbit]

It turns out that I had misread the power source, it was 9V AC instead of DC, luckily I didn't seem to damage anything with that and now it works fine with a 9V DC 500mA source I found.

[jbelanger]

Since there is a diode at the power input, the probability of damage from an AC power source is low. But it won't work very well if at all as you saw.

Good to see that you've got things working now.

Jean