coil signal problem

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freaky_fish
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Posts: 3
Joined: Sun Apr 20, 2014 2:54 am

coil signal problem

Post by freaky_fish »

I have a ms2 v3 megasquirt and have been having a problem with the signal from the transistor on Q16 the earth is fine and the voltage in is fine but the signal out is going from about 0.5v to 2.5-3v. On the stock ecu it goes to 0v how can I sort this out ?

Thanks
Paul
billr
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Re: coil signal problem

Post by billr »

No one else is chiming in, so I will ask some questions. You have a jumper in place of R43? How do you know the gate drive for Q16 is OK? That is a fairly short pulse, hard to evaluate without an oscilloscope. Are you measuring the Q16 output right at its output pin/pad, or further on in the circuit, like at the DB37 pin 36 or the coil itself?
Matt Cramer
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Re: coil signal problem

Post by Matt Cramer »

Is this measurement on the car or on the Stim?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
freaky_fish
MS/Extra Newbie
Posts: 3
Joined: Sun Apr 20, 2014 2:54 am

Re: coil signal problem

Post by freaky_fish »

Yeah we have a jumper on r43. Have been using a snap-on diagnostics machine which picks it up and shows it on a graph. This has been measured with it on the car.

Thanks for the replys
billr
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Joined: Sun May 15, 2011 11:41 am
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Re: coil signal problem

Post by billr »

Does that Snappy diag machine actually connect to the Q16 gate?
freaky_fish
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Joined: Sun Apr 20, 2014 2:54 am

Re: coil signal problem

Post by freaky_fish »

Yeah it has probes on it to measure anything.
billr
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Posts: 6828
Joined: Sun May 15, 2011 11:41 am
Location: Walnut Creek, Calif. USA

Re: coil signal problem

Post by billr »

Can you post a picture of the wave-form at Q16 gate? If not, what is min/max voltage, pulse-width, and approximate shape? Maybe sketch it and post the sketch. However, it may be more practical to try changing Q16 than to prove that it is good or bad.

Edit: The Q16 "output" to the coil, does that only go high to 3V? It should be up at 12V when the coil isn't being charged (Q16 "off"). Or do you mean that the Q16 output is going low to the .5 - 3V range? A wave-form there, also, might make it clear for me.
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