MS3 V3.0 board doesn’t have power with JimStim

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MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Sun Jan 28, 2018 7:28 pm

I just assembled the MS3 V3 board and I am at the point of starting to test with the JimStim. Right now the MS3 board isn’t getting power. 0v read at pin 20 of the U1 connector. Checked diode installation direction on D10, D11, D12, and D13. I also checked resistance to the heat sink at Q9 and Q12. Also checked power at U5 on the left pin. With the JimStim plugged in and turned on, I have 2.1v at the left pin on U5. Also what is weird is that when I have the JimStim plugged in (to the wall) and turned on I measure 3v on the JimStim battery lugs for the 9v battery. When I unplug the JimStim from the MS3 V3 board it jumps to 12v.

If anybody has any pointers or suggestions it would be greatly appreciated. Not really sure what the deal is, the board doesn’t have the appropriate power and won’t turn on and I am trying to figure out where to trace it back to, and why there is a voltage drop when I have the JimStim plugged in.

Thanks in advance.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby DaveEFI » Mon Jan 29, 2018 3:00 am

Check the tantalum caps (electrolytics) are the right way round. The (+) marking can be difficult to see, Don't plug in the processor until you have the correct voltages.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Mon Jan 29, 2018 11:57 am

Great, thank you. I will check those tonight and post a reply. Hopefully it’s something simple .... appropriate the help thus far.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Mon Jan 29, 2018 11:35 pm

So checked the capacitors and they visually looked ok, they didn’t have any burn marks on them. I checked continuity as well. Everything appears to be ok. There are no polarity markings on the capacitors. Only durning installation they had one pin longer than the other to distinguish polarity. I am at the pint of maybe pulling diodes off the board until I have power as per the trouble shooting section, but that doesn’t make too much sense as if I pull a diode off wouldn’t that just like going open circuit and still not have power on the board? pretty stumped but this is also my first MS build so trying to sort this thing out.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby racingmini_mtl » Mon Jan 29, 2018 11:39 pm

D19 is between 5V and ground. If this diode fails, it creates a short between 5V and ground and it looks like what you're seeing. Try to remove this one first as this is a rather common failure.

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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby DaveEFI » Tue Jan 30, 2018 2:20 am

With a small PS, there won't be enough power to burn out anything - which is a very good reason to use one when testing. With high power from a battery, there's a good chance of burning out tracks if a short develops, and no fuse used.
You can check most diodes in circuit using the diode test function on a DVM. That measures the forward voltage drop of a diode, which will be about 0.6v on a working one. Reversing the connections to the DVM will give a very different reading if the diode is good. But with the diode in circuit, this test doesn't always work depending on other components in that circuit. If it does, you can tick off that diode as being good.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Tue Jan 30, 2018 12:47 pm

Awesome thank you, I will check tonight after work and report back. Thank you all so much for the help
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Wed Jan 31, 2018 12:00 am

Checked the diodes and with my Fluke DMM this is what I have:

D9: .563v measured one way and OFL with leads swapped
D10: .569v measured one way and OFL with leads swapped
D11: .560v measured one way and OFL with leads swapped
D12: .702v measured one way and 2.48v with leads swapped
D13: .695v measured one way and OFL with leads swapped
D19: .385v measured in both directions
D20: .534v measured one way and OFL with leads swapped
D21: .803v measured one way and .524v with leads swapped

All these readings were taken with the board de-energized. Judging by the readings I am guessing that D12 is faulty for sure, and then D19 and D21 may be faulty as well?

Appreciate the patients and the help, and excuse my novice experience with the board assembly. I will be stoked when it works but trying to figure it out right now proves to be a bit challenging. Thanks again
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby kjones6039 » Wed Jan 31, 2018 1:21 am

2dubtech wrote:All these readings were taken with the board de-energized.

Are we measuring voltage or resistance here?

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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Wed Jan 31, 2018 1:30 am

I am in the diode check function on my multi meter and V is what is displayed on my screen.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby DaveEFI » Wed Jan 31, 2018 3:12 am

D19 definitely looks suspect.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby kjones6039 » Wed Jan 31, 2018 11:21 am

2dubtech wrote:I am in the diode check function on my multi meter and V is what is displayed on my screen.

Ah, yes. Gottcha!

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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Wed Jan 31, 2018 10:58 pm

Removed the D19 diode and no power still. I am going to order the D19
Diode and go from there and see why happens. I will replace it and report back, thanks again for all the help and hopefully that’s it but I will repost with my findings and an update.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby racingmini_mtl » Wed Jan 31, 2018 11:31 pm

Removal of D19 will not prevent the unit from working so if it's still not working don't replace D19 until you find the actual issue. You need to keep investigating the components and the board until you find the short.

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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Thu Feb 01, 2018 10:42 pm

Ok good deal, I will keep removing and post what I find
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Fri Feb 09, 2018 11:37 pm

So here is my status update. Removed D19, D12, D13,D11,D10, D21, D20, D9, D17, D5, and D7. At this point when I have the Stim board plugged into the wall by itself I have 11.9V available on pin 28 of the Stim. As soon as I plug the Stim into the MS3 that 11.9V voltage reading drops to 3.5V. Judging by this I still have a short or a major volt drop from a faulty component. I have flipped over the board and tried to find out where all the components are for pin 28 (supply voltage) but get lost in the maze. If anyone can direct me to a possible list of components that I can remove or check that would be awesome. I have been looking through the hardware manual to try and decipher the diagrams. Any further help or direction would be great appreciated. I apologize for my novice experience, really trying to not let this defeat me. Trying to learn from my mistakes, but need to find the source first.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby DaveEFI » Sat Feb 10, 2018 2:40 am

Check all the small transistors for a solder bridge short. A strong light and magnifying glass helps. Also check the two transistors on the heatsink which are insulated from it aren't shorted to it.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby 2dubtech » Sun Feb 11, 2018 9:37 pm

So checked the transistors across the heat sink. The lowest amount of resistance I read was 59.6 K Ohms. Thinking about pulling Q9, Q3, Q11, and Q12 one at a time to see if I get 12v back to the board. I looked with a magnifying lens and flashlight and could not spot and bridges. Right now I have Q12 and Q9 unbolted and not not touching the heat sink at all and still only have 3.2 volts available at pin 28 when I turn the Stim board on. Stim board plugged into the wall and with Stim board by itself I have 11.96 volts available at pin 28 from Stim board.
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Re: MS3 V3.0 board doesn’t have power with JimStim

Postby DaveEFI » Mon Feb 12, 2018 3:01 am

You seem to have one of the rarer faults. :shock:

I'd next remove the polyfuse F1, and check again. That will show if the short is associated with the 5v rail. And check you have 5v on the output of the regulator. Refit any diodes etc you've removed which are part of the power supply.
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