Need Help diagnosing problem with P&H board

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Need Help diagnosing problem with P&H board

Postby crustyshadow » Tue Jun 17, 2014 6:18 am

I have a problem that im not sure how to diagnose.
I have a MS3 with the MS3X card installed, Unaclocker's MS3X modification to bypass the MS3X injector drivers, and that is connected to a v1.1b board mounted externally in its own case separate from the MS3. I was testing injector outputs in test mode, but as soon as I plugged in injectors channel C and D were stuck "on". I was able to eliminate the wiring harness as a possible cause on the input and output of the P&H board. from what I can tell I may not have had the FETs for channels 3 and 4 properly isolated from the case- the shoulder washers were a bit distorted and were showing continuity between the INJ and GND of channel 3 and 4. so I unbolted them from the case and they are sitting completely separate from the case and not touching anything. in test mode I get nothing from the outputs. I know I am getting input to the board, I verified that with a DVOM- I can see it pulsing on the input pad with my meter. I also have good ground to the input pad as well as 5v. im not sure how to diagnose what is going on beyond that.
I do have a scope but not too sure how to use it properly.

I would be grateful for any help
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Re: Need Help diagnosing problem with P&H board

Postby jbelanger » Tue Jun 17, 2014 9:28 am

You will not measure anything from the outputs unless they are connected to the injectors because they provide the ground.

So to test them, you need to connect a source of voltage to the outputs such as a pull up resistor. You will then have the pull up voltage when the output is off and ground when it is on. If you have a JimStim, you can use the LEDs for this.

Also, check the polarity of the large diodes. Having them in the wrong direction will also lead to stuck on outputs.

Jean
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Re: Need Help diagnosing problem with P&H board

Postby crustyshadow » Wed Jun 18, 2014 6:03 am

ok I found the problem.
two of the mica insulators was bad. I probably over tightened the mounting screws when installing it into my case. I just happened to have a replacement from the stash of extra parts from my last MS, replaced the mica insulator and the through hole isolator with leftovers from the DIYautotune MS kit.
one thing I noticed about the replacements I used was the DIY Mica was considerably thicker than the ones supplied with your kit and the through hole isolator also fit better and the smaller nut and lock washer were a bit easier to work with. you may want to consider ordering those same pieces next time you order parts.
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