snapped,shorted 5v throttle wire, help needed

[jimmyhackers]

my friend has a 3000w hub with 3000w esc.

some how he managed to blip the throttle while not on the bike and the result was a snapped throttle cable.

after various troublshooting.....i discovered the 5V regulator part that feeds the throttle is only outputting 0.45v.

i assume as the cable snapped it shorted out the 5v to the ground and popped that regulator part.

essentially the main 5v chip is only being fed lesss than a volt.....so i think it how the powers being fed to that thats gone wrong and not the chip....

i have attached a pic of the board......anyone care to point out which compnents are most likely to be dead n need replacing?

TIA
Jim

 

[jimmyhackers]

here is a closer pic of that regulator part.

 

[markz]

Well the problem is that there could be upstream and downstream components that have fried, any op-amp chips for example, then if there's SMT (surface mount = very small = may need a microscope) components makes it even harder to fix, many integrated chips are SMT. Capacitors could be toast who knows.
And since everything is in a circuit, makes it even harder to troubleshoot and even harder to diagnose which components are toast. As apposed to having a component itself, in your hand, on your desk to test and measure. Resistors for example, if a resistor has fried, with no visual damage, then if its in parallel you'll get still get a reading of the parallel network.

But going with the obvious fixes first is the right approach.
Any black marks, replace, any visual damage, replace.

Aside from all that, hopefully that controller wasnt an expensive one and just a generic cheap controller in which case just buy another.

 

[jimmyhackers]

i have the thing in my hands......cant really see much visual damage

only thing that looks a litttle fried is that largish green resistor. on the underside it looks a little burnt.....but not a lot.

0 conductivity or infinate resistance on a multimeter.

annoyingly the colour code is black black white gold..... whichmeans its 0ohm reisitor :S pretty srure they dont exsist.....

 

[TrotterBob]

I dont have a definitive answer for you, but 0 ohm resistors do exist. Shouldnt be too hard to match that one with something similar online.

And 0 conductivity or infinite resistance just means an open circuit. Basically its fried.

 

[jimmyhackers]

i did a bit more googling and you're right, 0 ohm resistors do exsist....

cant find an exact replacement easily though. :s

as far as i can tell.....its easier for a machine to put in a 0 ohm resistor than a jumper wire. as that's essentially what they are.

they can also be used as a cheap fuse.....so hopefully its only this thats gone pop.

im umming and arring what to replace it with.....knowing my friend this will happen again....so i need something that will go pop.
im contemplating a very small car fuse.... 1a, 0.5a or even 0.25a or something....but i worry even that will be too big.

 

[TrotterBob]

Do a bit more research on 0 ohm resistors. I think they still limit current. So I dont recommend swapping it with something else, it might cause issues with other components.

Thats just a thru hole resistor. You should be able to score a handful of them on feebay for around $5 shipped. Not sure if yours is 1 watt, 2 watt or 5 watt. Doesnt look big enough to be a 10 watt.

Try this: https://www.ebay.com/itm/324683051749

 

[markz]

I got no clue what color code that is but maybe there is a different numbering system for a 4 band system vs a 5 band color code.

0 ohm resistors are sense wires, but I never seen one bulky zero ohm resistors unless you have the color code wrong, color itself, or reading the color code wrong, from the wrong direction.
I am done trying to fix things, but spent many hours trying to write a schematic and trouble shoot stuff. Gets very confusing because the pcb's can come in various layers, like say a 5 layer pcb so cant trust what a visual pcb track is doing, could be going anywhere, multiple spots.

There is a difference between zero ohm and infinite resistance
one is the resistor is blown and acts like a cut wire (infinte ohm)
the other is an intact wire (zero ohm) but in all reality its not truly zero, just miniscule resistance, milli-ohms. I buy cheap multimeters, broke 2 or 3, but right now I got 3 or 4 scattered about. Not like it can read ##.##V, just ##.#V and whole number ohms. The expensive Flukes could probably read mOhm.

 

[jimmyhackers]

its fixed.

that 0 ohm resistor was used as a fuse, nothing else. i kinda half figured by its placement it would be a fuse instead of a resistor. (multi pin holes aswel)

thing crumbled a little while being removed. apparently china does things like this for various reasons....

i figure the main one is if they put a replaceable fuse holder there...customers would change the fuse when it goes.

instead of buying a whole new unit when it breaks. (sneaky china men)

i figure also any returns they get from a "broken esc" can be easily fixed with a cheap part.....thats disguised as a resistor (which most people wouldnt try and replace at home).

ive soldered in some slots so if he pops it again he can replace without soldering.