Boot jumper voltage low.

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Dougal
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Posts: 36
Joined: Wed Feb 15, 2017 1:16 am

Boot jumper voltage low.

Post by Dougal »

I have newly finished an MS2/v3 board and have correct voltages at all the recommended test points except the boot jumper which reads .6v with a supply of 11.7v. R3 and R6 resistànces are correct and I can't find any other errors or solder bridges etc.
Firmware loaded successfully and Megastim works fine. I have completed input testing on the car and also the IAC stepper motor test.
My question is whether this voltage error will cause problems down the line? And what other tests could I do to find the cause?
Thanks for any advice.
Dougal.
slow_hemi6
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Joined: Fri May 07, 2004 3:33 am
Location: Australia

Re: Boot jumper voltage low.

Post by slow_hemi6 »

Dougal wrote: I have completed input testing on the car and also the IAC stepper motor test.
Dougal.
I am a bit surprised you continued on when you did not get the 1/6 supply reading expected at H1. So what did the battery voltage read when you did the input testing? If it read about the same as the cars battery voltage then the issue would be with the soldering of the boot jumper or the testing because the circuit is working correctly. If not then there is a problem there. With the daughter card out the only components involved are R3(50K), R6(10K) and the boot pins if you installed them.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
Dougal
Helpful MS/Extra'er
Posts: 36
Joined: Wed Feb 15, 2017 1:16 am

Re: Boot jumper voltage low.

Post by Dougal »

Hi,
Thanks for your reply.
Well, I continued because all the other voltage tests were correct and I figured that since the voltage was low, at least I wouldn't do any harm!
I'm testing across the 2 unused H1 solder pads so if that's correct not much to go wrong with the test.
The left pin of U1 measures about battery voltage with the daughter card removed and slightly less with it installed. Tuner Studio gauge shows about battery voltage.
So what does that circuit do if the jumper is never used? Is it connected to the daughter card boot load jumper? (I had no trouble loading the firmware).
Anyway I would like to correct it!
If only 2 resistors are involved, and they do have correct resistance and are installed in the correct position, it can only be a connection issue. I shall remove and replace them.
Should I get battery voltage at the top of the first and a progressively reduced voltage at the bottom of each? And presumeably a good ground on one of the H1 pads?
Many thanks, Dougal.
slow_hemi6
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Posts: 4122
Joined: Fri May 07, 2004 3:33 am
Location: Australia

Re: Boot jumper voltage low.

Post by slow_hemi6 »

The circuit has 2 purposes when used with MS1 processor. 1. the resistor divider of R3 and R6 provides a 1/6th supply voltage to pin27 (AD4) so the MS1 processor can use it 0 to 5v analogue input to know what battery voltage is. 2. it puts the processor into boot mode when the jumper is in place. It does this by grounding AD4 so the processor sees 0v on power up and goes into boot loader mode.
In MS2 it only does the voltage measurement as the MS2's bootloader is on the daughter card itself.
You do have to be careful with this circuit because if R6 were to be open circuit 12v could be applied to AD4 and even though 50K resistor is in series it might kill the 5v ADC input.
Is your multimeter auto ranging? any chance it is just not on a good scale to read the 2vdc?
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
Dougal
Helpful MS/Extra'er
Posts: 36
Joined: Wed Feb 15, 2017 1:16 am

Re: Boot jumper voltage low - NOW SOLVED.

Post by Dougal »

My multi meter is auto ranging. It's a Fluke 116 True RMS.
I just did another couple of checks.
I have 12.4v on the top leg of R3 and .6v on the bottom leg. So no soldering connection involved! R3 resistance is 51k.
Now I've just re-tested with a £13.99 multi meter I keep as a spare.
And guess what? 2.0v across H1!!!!.
So that explains why no problems!
So problem solved as far as the board is concerned. Now to the Fluke!!!
Many thanks for the help.
Dougal.
slow_hemi6
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Posts: 4122
Joined: Fri May 07, 2004 3:33 am
Location: Australia

Re: Boot jumper voltage low.

Post by slow_hemi6 »

like my old fluke t5-600, always caught me out on not measuring under 1ohm.
Find the Manuals up top under Quick links: Manuals. :RTFM:
Cheers Luke
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