Large Voltage Drop from Arpicade to Pi

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Sdscribe
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Large Voltage Drop from Arpicade to Pi

Post by Sdscribe » Sat May 09, 2020 1:26 am

New user here. After install I was trying to rectify the pesky Raspberry Pi low voltage warning, but am seeing a large drop from Arpicade to the Pi.

Initially I had 5.1V at the harness, tried to dial up to 5.2 but lighting bolt wouldn’t disappear.

Decided to measure the voltage from the pi test points (PP3 and PP7) instead and dial up the power supply using that as reference . Got the pi to 5V and the bolt was gone.

Went back to measure the 5V at the Arpicade board’s edge connector. Read 5.44V.

That spooked me a bit so I dialed it back to 5.25 on the PCB and the pi runs around 4.85. Thought that would be a happy middle until I sort this out, lighting bolt and all.

Does this seem normal? Could there be an issue somewhere on the Arpicade that would syphon off that much voltage? I assume running 5.44 volts into the Arpicade is not within specs.

Any suggestions to dial this in properly would be appreciated. Thank You!

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Re: Large Voltage Drop from Arpicade to Pi

Post by dee2eR » Sat May 09, 2020 2:45 am

What model Pi are you using?

Sdscribe
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Re: Large Voltage Drop from Arpicade to Pi

Post by Sdscribe » Sat May 09, 2020 3:07 am

The 3 B+

Arpicade 3.9

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Re: Large Voltage Drop from Arpicade to Pi

Post by dee2eR » Sat May 09, 2020 3:15 am

That definately doesn't sound right. For reference my bench power supply is set to 5.18v (at the power supply), I have 5.08v at the JAMMA edge - no lightning bolt (unless I'm compiling and all 4 cores are 100%...).

Is you RaspberryJAMMA board new? The early boards had 1A fuses, later boards (made in the last year or 2 or so) have 2A. If you have a 1A fuse upgrading it to 2A or 2.5A will probably fix the issue.

What is your JAMMA harness like? Lots of new ones have inadequate power wiring as they're basically intended to just power a 60in1. If you only have one 5v wire from the power supply to the harness I would recommend adding another 5v and GND wire to increase the JAMMA harness' current handling capacity.

Beyond that, is there any damage to the ribbon cable that joins the RaspberryJAMMA and RPi? The power has to get through it so if it has been damaged it could also be the cause.

If your power supply is old and out of spec/failing it could also possibly be the cause.

There's not really anything else on the RaspberryJAMMA PCB that could be the issue, unless you have track damage on the underside of the PCB.

EDIT: I have 5.08v at the JAMMA edge - I forgot to write the decimal

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Re: Large Voltage Drop from Arpicade to Pi

Post by Sdscribe » Wed May 13, 2020 7:51 pm

Had a single large 5V wire running from the power supply. Took it off the harness and low and behold....it was about 1/1000 of actual wire and 999/1000 insulation. It was borderline comedic. Added another 18A gauge wire to the both 5V and the Ground.

Now reads 5.11V at the power supply and 5.09V at the Raspberry Jamma fingerboard. No lightning bolt in sight after a few hours of testing/dialing in.

Thanks for the help!

I bought the board new last week, but for possible future reference, is there any way to visually identify which Raspberry Jamma board version (1A vs 2A fuse) one has?

Thanks.

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