MS1 3.0 board question

[tkozlow1]

Hi, I'm new to the forum and the MS world. I have read as much information as I could before even buying the MS and
now I have purchased one and the stim. I assembled the stimulator and started on my ECM. After step 23 it stated to test the ECM with the stim. I powered up the stim and attached it to my ECM. I tried 2 different ac/dc adapters. 1 was a 12v 300ma and the other was a 9v 500ma. I tested both prior to hooking them up, and they both work. I cannot get my voltages I'm supposed to have on the 40 pin connector or at the voltage regulator. I am very particular and anal about my work,
but I double checked as per the troubleshooting section and found all of my components in the right place and no bridged solder. I did notice my 12v zener diode got very hot in the process and since troubleshooting said to remove one leg of a component at a time until the voltages come on line I started with this diode. Needless to say, it broke whenI went to remove it. I then tried to register to this site which wasn't easy and googled as much as I could. I then decided to try the 9v battery connector on the board next to the ac/dc adapter port and then I got all of my voltages. So my question is why won't my ac/dc port supply my power properly? I did unsolder it and check for bridged solder, but there was none. Please help! Thank you in advance!

Tom

[trakkies]

My initial guess is the polarity of your mains adaptors is wrong. Check the output plug with a DVM.

FWIW, you may have problems down the line trying to load in code with 300mA supply - even although MS appears to be ok with it. If you have to buy a new one, go for a 13.8v 1 amp unit. That has plenty power for checking most things MS - including it driving a relay or two. But not so large it will smoke things if you have a fault.

[Bernard Fife]

tkozlow1,

Be careful about power supply that are rated above 12V or 500 mA. That's because most of these "wall wart" style adapters are unregulated. That means if the current draw is less than what the supply is rated at, the voltage is higher. MegaSquirt typically draws about 200 mA to 300 mA. An unregulated 13.8V 1A supply could easily put up to 20 Volts into MegaSquirt. MegaSquirt is safe up to about 17 to 18 Volts. Supply voltages higher than that can damage components.

I have burned the flash memory of MegaSquirt controllers thousands of times with a 250 mA 12V supply. So that shouldn't be a problem.

Failing wall warts are common, and you often need a scope to see that problems in one that is starting to fail.

Was it D13 that was getting hot? This is the only 12V Zener in the power supply on a V3 board. If it is getting hot, then it is likely that the D11 diode is either backwards or fried.

There are lots more tips here: http://www.megamanual.com/ms2/V3trouble.htm

Lance.

[trakkies]

Sorry - should have said a regulated supply. However, pretty well all the new small current 13.8v ones on sale in the UK are.

I only mentioned having had problems with a low current supply when loading code because I've experienced it. I'd guess you use a good quality bench supply with variable voltage and current limiting. Some wall warts may be a bit optimistic in their claims.