Fixing older wheel & controller, are all hub motor transistors similar?

[Scorpio]

Hi folks, I'm trying to find why my older Dutch town bike (with slightly newer aftermarket kit) has died.
It look like the fault is down the yellow phase transistor in the hub.
I swapped the wiring around, the fault stayed with the transistor so it's not a wiring issue.
I removed the yellow signal wire at the hub end and checked the transistor, even with no output wire connected I get zero volts (the 4.5V feed and earth check out ok) - it's dead Jim !

Tests were done with a charged 36v battery (showing 38v), the wheel has been opened up and I'm turning the motor backwards to check the voltages on the phases - it's the way I usually do tests...
It's a basic old system and getting parts out here (Portugal) is difficult so I'd like to try fixing it using what I have here.
The harness is old-school with block connectors not waterproof bullets so it's easy to check voltages.


I have a scrap hub motor from a 24v system (scrapped due to old age and wrecked motor cable) but I think the hub transistors all work on 4,5v so they should be swappable'ish.
My question: will a transistor from the scrap hub be compatible with the hub currently on the bike - if so I'll swap one from the old hub to new.


I picked up a 36v controller and display "working well - honest guv" as a spare, It turns on (with just battery and display connected, no PAS etc) but then turns off again after a few seconds. Is this normal ?
When it's on, I'm only seeing 2.5v on feeds to the PAS, brake cutofffs etc when I'd expect 4.5v
I think this means it's dead but maybe I've missed something?.
It's 36V/48V compatible, I can get into the P settings but have no manual to decode what I see, my only hope is it's in 48V mode and is seeing the charged 36V battery as below LVC - any way to check?


Background info possibly relevant : The problems started when let a friend of a friend (now known to be an irresponsible fool) borrow the bike, he has snapped the rear rack which has strained the harness in that area but I don't see how that could be related to a failure in the front hub...

I have time and a pile of bits, asking here in the hope I can patch a working system together somehow...
All suggestions (apart from "buy a new..") welcome

 

[thelarkbox]

how many wires in the brake sensor connections?? if only 2x the 2.5v could be the NOT grounded floating voltage?? if the controller label has (Brake:Low) on it it would indicate the brake cut off is grounded to invoke.

I doubt the 24v controller mosfets would be tolerant of 48v if the higher tolerance requires a higher cost component. if no visible component ID try wiping with a solvent to moisten the chip and perhaps reveal an id you can google for a datasheet.

 

[AntonyC]

Like you I'd guess the transistors will be compatible voltage-wise but could have different pinout, a component tester should sort that out, or a meter will ID the base and you've 3 spares.
Fully charged 36V is 42 actual volts, 48V LVC could be 40V or 41V. Controller might turn off if it doesn't see a motor - well you didn't mention one ;-)

 

[saneagle]

I think people are getting mixed up because you're calling the hall sensors transistors. If there's a suspicion of cable damage, you can check the yellow hall sensor function and supplied voltage at the hall sensor itself inside the motor. All thos hall sensors work the same, so should be OK swapping from one motor to another, or you can buy them really cheaply, which is easier than digging them out of a motor.

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There are some occasions when you need a pull-up resistor to make them switch. The resistor can be in the controller, on a pcb in the motor or even integral with the hall sensor, so if a new one doesn't switch, just add a 5k resistor between the signal and 5v legs/wires.

All such hall sensors work at 5v.

 

[Scorpio]

Apologies for the confusion, yes the problem is the hall sensor in the wheel - I couldn't remember the proper name so was calling it a transistor. Oops.

Pinouts match between halls on the scrap and new hubs, I've pulled one out of the scrap hub, will look at pulling the dead one out of the new hub in daylight.

First tests were done at the controller end of the harness, I soon opened the motor up and since then have been testing at the actual legs of the halls just to eliminate any wiring issues.

Thanks everyone for the help and suggestions !