Hi, so our vrm stopped functioning abrubtly and it wont work. 12 Volt is coming from the PDP but when it comes in the VRM no output is coming from both rails and the leds are off. Please help me on any solution I can do to power my modem.
If this is for off-season use, then any buck-boost power converter you can obtain locally that operates on a minimum voltage like 5v or 6v and outputs 12v will work.
The stress on the robot battery voltage is a lot less for driving at demos and practice.
If for competition, then Spare Parts will have a replacement VRM that you can borrow for the duration of the event.
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It sounds like you need to replace the VRM. Legally, you need to power the radio only from the VRM 12V/2A ports. Do any teams near to you have one they could give to you in the meantime?
If you only need to power your radio, consider the REV Radio Power Module, otherwise, check that none of the wires in the VRM are frayed and shorting out.
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how do I check the VRM if it’s frayed? visually I cannot see any burn marks, aluminum shavings etc. also what tests can I do to identify where in the VRM has the problem?
what is “Spare Parts”? is it like a place in the competition where you can get replacement parts? our team is going to worlds this year and does frc worlds have that kind of thing?
What MarkG. means is to make sure you don’t have any “whiskers” from the wires you put on the VRM that could be shorting out to the wires next to them. Sometimes when putting the wires into the connectors, an errant strand of wire can bend out and touch the other wiring, causing a short.
And what MarkM. said is that yes, at competitions, there is the Spare Parts table at Pit Admin, and they should have spare VRM(s) for teams in case one fails and the team doesn’t have a spare.
And I see that CTRE is out of stock on the VRM, so MarkG’s suggestion of seeing if you can get a REV Radio power module to take the place, if you’re only powering the radio from it.
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Yes.
In Houston, if the layout is similar to past seasons, Spare Parts will near the Machine Shop desk up against the back wall of the pits area.
There will be 8 fields worth of Spare Parts available.
The image I gave is the inside of the vrm. Can you see any burn marks? I’m not a pro on these and I really need to know if its frayed or not…
Sorry if I wasn’t clear. The wiring I mean is what you push into the spring connectors. What I meant was this (different style of connector, but same idea):
You see how there is a strand or two of wire that didn’t quite make it into that connector? Things like that can cause shorts and damage internal components.
However, since you’ve opened up the VRM, what I show in the circle there is concerning. It appears that chip is pretty damaged, so I would dare say this VRM is not usable.
ETA: I sent a close up of that chip to a friend who does chip replacement and diagnosis for circuit boards, and he said the chip definitely overheated and is damaged.
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Please slow down and read the responses to your query more carefully and thoroughly. What @MarkGhebrial and @Zagar are talking about is frayed WIRES, not your VRM.
How I detect frayed wires and exposed conductors when they are inserted into the connectors on the VRM is to use a bright flashlight and shine it around where the wires enter the connector. You should not see any shiny metal. The insulation should go into the connector a little bit so that the plastic body of the connector and the wire insulation overlap a little. If there is any length of exposed conductor, you are vulnerable to that wire getting shorted.
It is also possible that one of the strands did not go into the connector and is (almost) touching the adjacent wire(s). The bright flashlight will also make these stray strands show up.
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Thank you for a response, although my response is late I thank you so much for dealing with our questioning. What you explained shows why it doesn’t work I guess. Is there any way of fixing it though?
In my opinion, no, it’s not worth fixing. They aren’t so expensive nor are they something that’s (usually) difficult to find, so replacing it would be the better option. Besides, you can’t know if any other components were damaged besides that one. Chances are quite good that one or more of the surface mount resistors are fried too.
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