Broken V5 Ports... and How to Fix Them!

Sorry. Incorrect. One is plastic and decorative. The other is metal and directly contacts the motor housing.

I will look into this. I have a motor opened at our club. I thought both sides of the motor were just plastic.
Photo Sep 05, 4 25 20 PM
This is a picture from the teardown by @sazrocks. I will look into it this evening as we have a couple of broken motors.

2 Likes

Looking at the pinout, the Analog LTC2862A seems to be compatible, since it is also a TIA-485 chip. It is claimed to have pretty good ESD protection built in, so it might be worth looking at for repairing brains (for classroom use, of course)

Only thing is, there are several models of that chip and I can’t figure out which one would be right for this use case.

1 Like

You can hear the difference. Pull your fingernail, or any hard object, backwards across the fins. Significant difference in sound.

I will note, the anodizing is usually NOT electrically conductive, so you would need to scrape it away to properly ground to it. And all this assumes that grounding the heatsink (and motor can) is the proper place to ground to.

motor
This is the motor PCB backside from one of our dead motors. The chip circled in red is the RS-485 to UART chip that if replaced could make the motor work again. With motors there is also an H-Bridge chip that could be dead.

3 Likes

Thanks for this! I was going to mark the chip, but didn’t get time to write this. In general, if the motor wire LED is flashing, even when connected to a known good port, this RS-485 transceiver is dead. If the motor reads as connected, but still wont spin or makes a whining sound, its probably the h-bridge mosfets. That fix is out of reach for most and the motor is probably dead. I have also experienced a capacitor failure which prevented the motor from powering at all. Replacing it fixed this issue.

1 Like

This is wrong. The center case of the motor is a single injection-molded piece of plastic. There is no metal. This is very clear from a basic disassembly of the motor, where we can see that there are no seams or gaps that would indicate the presence of a separate part made of metal:
image image
You can even see the injection molding marks on the area you purport to be made of metal.

I even scraped away the surface of the area you said is metal and found only plastic underneath:image

13 Likes

I stand corrected. The difference in sound, appearance, and direct contact to the motor’s can led me to believe is was metal. Still sounds very metallic when you rake across it with something hard. Ideas on that?

The different lengths of the fins of plastic lead to a different pitch of sound when struck. Think of the strings on a harp, or the effect that different finger positions have on the pitch of a guitar.

3 Likes

I’ve got that part. Thing is, they are longer/deeper than the other side so the sounds should be lower. It’s not. And it’s got a distinctly metal sound like cooling fins on a small engine, cpu heatsink, etc. Very strange.

You are saying that something vex made is weird. Why are you not surprised? Vex tries to make them as complicated as possible so as to make them harder to reproduce by anyone other than their own factories.

1 Like

Its been a while, but a friend of mine did a great job creating a step-by-step guide for repairing a v5 brain. It is much improved from my text guide and adds from lessons learned after I wrote my original post. If you are at all interested in repairing your, give this a watch!

13 Likes