Ajb

Well i finally finished my megasquirt build and found someone local to me with a stim finally. I decided Id quickly hook it up without DB9 cable or anything to see if anything would flash.

Nothing happened and when I took the 9v battery off the stim it was very hot. Is that normal ?

Braineack

iTrader: (62)

it wont light up anything until you flash the firmware.

Ajb

Well im not sure whats happening im trying to write the files through easy therm but I cant seem to get any connection to the megasquirt.

Im not sure if there is something wrong with the stim as when I hook it up the battery gets so hot I can hardly touch it. Might just try to write the stuff while megasquirt is hooked up in the car ?

Matt Cramer

Sounds like there might be a short. Are any components on the board getting hot?

Ajb

I just checked the board and I cant feel anything getting hot at all. I also checked the stim and it seems to be giving no power on pin 28.

I did the check for voltage with the stim hooked up and im getting nothing on the processor board.

Edit : just did some checking and the stim i was given was a V2.1 but i never got a 12 power supply connector. Ive just been using a 9v battery does that work or do I need both plugged in.

Matt Cramer

9V batteries work but have a short lifespan on the Stim.

Joe Perez

iTrader: (8)

There are two major stim families (the original, and the JimStim) however there are no limitations in terms of using stim X with MS Y. They're all compatible. The big difference is that the JimStil gives you lots of extra features, such as twin-triger output (necessary to test a Miata MS)

If the stim is giving you no power out on pin 28 while the MS is disconnected, and the battery is getting hot, then you've got a short on the stim, plain and simple. If this is a JimStim (the one with terminal blocks on it) then I'd suggest you start by removing all jumper wires from the stim and giving it a good eyeball inspection top and bottom. Schematics for the JimStim can be found here: http://www.jbperf.com/JimStim/index.html (note slight differences between 1.3 and 1.4 boards)

Info and schematics on the regular stim here: http://www.megamanual.com/v22manual/v1stim.htm


EDIT: your recent edit, indicating ver 2.1, tells me that you do not have the JimStim.

Ajb

It is definatly shorting out when connected to the MS as the battery is fine when just connected to the STIM. Can the residue left by soldering create problems.

Im very confused as i would expect something on the MS board to get hot but nothing is.

Joe Perez

iTrader: (8)

Well, that's a problem.

If the short was due to a failed component on the MS, then I could see it producing some heat. D12 being backwards, for instance. (Though I'd expect D12 to blow up in that situation.)

On the other hand, something like a solder bridge between two pins would likely be able to carry enough current to drag down the battery without actually becoming terribly warm.

It's time to start probing around with a multimeter on the MS board. For starters, measure between each side of D10 and ground. If you get a zero (or near zero) resistance on either side, you've narrowed things down considerably.

Ajb

Well I just checked using the plug number 19 as ground of the main processor plug. On one side I get ground on the other im getting a resistance near the same as i do for the postive power supply on pin 20.

Edit : not sure if this is usual but D12 one side im getting major resistance and the other is grounding.

Im pretty much grounding on all of the top row for the DB37 and one pin im grounding on the bottom is pin 29. Could my short be somewhere along this line?

I have found with the stim attached im only getting something like 0.030volts to the ECU. Some major resistance in the line.

ScottFW

iTrader: (4)

The battery getting hot definitely means there's a short. Could be a solder bridge, or a blown or improperly installed component. The 0.03V reading isn't due to "major resistance;" it's due to almost zero resistance between power and ground.

Measure U5 and see if you've got ~9V on one side and 5V on the other. When that fails then double check the orientation of your diodes and electrolytic caps, make sure the components along the heat sink bar that are supposed to be insulated with the mica wafers are indeed insulated (high resistance between them and the bar) and make sure you've got no solder bridges. Basically, follow this first and go from there.