leds are dead

Ask questions about DIY board assembly issues, fault finding and testing. (Covers all Megasquirt versions and board.)

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foster650
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leds are dead

Post by foster650 »

i have had success in testing coils and injectors. but when i hooked it up to try to fire the engine the leds were lit up, the they went out one by one. now i have no igniton trigger to the coils. injectors still function. it is a ms2extra with ls coils running wasted spark. i have a msq listed in general under please help a total noob! would appreciate any help

i had issues with my jim stim where i fried the cpu for it. i am thinking i might have fried the ms2 also . i didnt see smoke and nothing is getting hot that i know of
foster650
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Re: leds are dead

Post by foster650 »

Matt Cramer
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Re: leds are dead

Post by Matt Cramer »

Try powering up the MS2 without a CPU, then apply 5 volts to pins 7, 8, and 9 of the U1 socket. Does this make the LEDs come on?
Matt Cramer -1966 Dodge Dart slant six running on MS3X
foster650
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Re: leds are dead

Post by foster650 »

matt i will try that when i get home.....i did check before posting and i had 4.9v on the leds...it seems like they arent getting grounded but i will check tonite. thanks again...still need to order the chip for the jim stim... lets see if that is the only thing lol
foster650
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Re: leds are dead

Post by foster650 »

ok.... tried the 5v to the pins 7 8 9 of u1 with cpu removed. no lighting up. checked with voltmeter and I have 5 volts on leds on ground side of led. which leads me to believe the cpu is toast. if I ground the ground pins on the leds they do light up. if I did kill it is there anything else I could have got? is it better to start all over? ( ugh) thanks man even if it is bad news.
slow_hemi6
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Re: leds are dead

Post by slow_hemi6 »

Sounds more like the led transistors are not switching.
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DaveEFI
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Re: leds are dead

Post by DaveEFI »

foster650 wrote:ok.... tried the 5v to the pins 7 8 9 of u1 with cpu removed. no lighting up. checked with voltmeter and I have 5 volts on leds on ground side of led. which leads me to believe the cpu is toast. if I ground the ground pins on the leds they do light up. if I did kill it is there anything else I could have got? is it better to start all over? ( ugh) thanks man even if it is bad news.
5v to pins 7 8 9 is how the CPU switches then on. So if the LEDs don't light the problem is on the PCB. First check the drive transistors Q6,7,8 are the right ones and have been fitted correctly. Use a strong light and magnifying glass to check for solder bridges as the transistor pads on the PCB are very close together.
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foster650
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Re: leds are dead

Post by foster650 »

ok.... i checked for bridging and dont see any and i check with dvom on the bottom side and dont seem to have anything dead shorted. they are 2n3904 d13 transistors and the manual calls for 2N3904FS-ND which i think are the same. i have a electronics installed here where i work and i will have him look at it too. i brought it to work with me so he can check it out.
DaveEFI
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Re: leds are dead

Post by DaveEFI »

If they were working before and now none work with this test, it's likely a common cause. Have you checked there is continuity between the emitters on all three transistors (which are grounded) - and that they are also connected to the PCB ground?
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foster650
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Re: leds are dead

Post by foster650 »

they do have continuity and are grounded at the emitter. i checked each individually.
foster650
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Re: leds are dead

Post by foster650 »

Hello again guys! Been away for a while and now I am back to trying to figure this out. I have purchased a new CPU for the jimstim from the awesome guys at diyautotune , but still having the same problems. LEDs on the ms2 are still dead and a am thinking of rebuilding the spark drivers with the tc4427 chips. Does this way seem to work better or is there somewhere stateside I can send it to to fix it. I have been thoroughly disgusted with this that's why I just steeped back. Thinking of possibly going the sloppy mechanics way and getting a msd 6010 to do the spark side of it if I can't get it going. Please guys I need some guidance ! Thanks in advance!
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Re: leds are dead

Post by Matt Cramer »

I haven't tested the TC4427s myself, but they'd bypass anything to do with the LED circuit and take it out of the equation.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
foster650
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Re: leds are dead

Post by foster650 »

what triggers the leds to flash? they have power but something is not grounding them.. i know sooner or later i will figure it out. the snow will fly here soon so i will have lots of time to mess with it i am sure. thanks again matt!
slow_hemi6
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Re: leds are dead

Post by slow_hemi6 »

The transistor switches the leds to ground when cpu provides approx 5v to the transistors base. The resistor between the cpu and the transistor is there to limit the current. The cpu can only safely supply a few mA. Having the resistor in there also means there is a voltage drop across it and you would not see 5v at the transistors base but a actually a bit less.
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foster650
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Re: leds are dead

Post by foster650 »

i am going to replace the transistors and the leds. 2 of my leds are open so i guess i need to replace them. i am going to look at the modifications i did also. thanks for the help and i hope to post better news later! :RTFM:
foster650
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Re: leds are dead

Post by foster650 »

i have a question guys, why are the leds 2.1 volt when they see 5 volts? and the leds should be flashing or out? i have new leds by the build sheet and it said 2.1 v on them. just a question. the 1st two leds from the db9 connector are staying lit up while the 3rd one is nothing. i have now power there which leds me to beleive that the transistor is bad on that led. thanks!
slow_hemi6
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Re: leds are dead

Post by slow_hemi6 »

As I said earlier, a circuit with a series resistor will always have a voltage drop across the resistor. This is why the led's have a 330 ohm 1/4 watt resistor between them and the 5V supply.
By the way led's are not rated by voltage. They are rated by maximum forward current in mA. With knowledge of your supply voltage you choose a series resistor that keeps the led's current on the right side of it's maximum.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
foster650
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Re: leds are dead

Post by foster650 »

So on the ground side if the led I should have 330 ohms resistance when I check continuity to ground? I know about voltage drops,, this is my diary go around build my own circuits. Usually I am trouble shooting a circuit for a problem in operation, I just haven't studied this enough to understand everything about this side of it thanks again man!
slow_hemi6
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Re: leds are dead

Post by slow_hemi6 »

Look at the schematics. http://www.msextra.com/doc/general/ms2v3schems.html Scroll down to the led indicators drawing.
There is nothing between the cathode(ground side) of the led and ground but the transistor. It should therefore be self evident, that when you look at the transistor as being a switch (open when no base drive present) that measuring to ground will reveal nothing as the circuit is broken at the switch(transistor).
Measuring from the 5v rail to led anode will reveal the series resistance, and measuring to the led cathode will show total series resistance provided of course you have the correct meter lead polarity. The led is, of course a diode and the multimeter leads are positive and negative when measuring resistance. Diodes do a pretty good job of only conducting when connected with correct polarity. A diode will also have a nominal forward voltage drop of about 0.6V.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
foster650
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Re: leds are dead

Post by foster650 »

Ok I removed the 2n3904 transistors and the LEDs . But I have resistance between the collector and the base terminals on the first 2 transistors and nothing on the third (going from the db9 connector ) when I the resistance is like 350 mega ohm until I remove the daughter card. Then it goes to nothing or open circuit. I am just wondering if I have something really screwed up or is this normal? Thanks
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