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ub0211042
2007.08.28, 03:12 AM
hi guys,

i used to have lot's of FETS problem :( :( :( :(
now a new one just happend...

after i install the fets, the car runs well can do couple of laps without any problem then the car just won't go forward.

put it to rest for a minute or two, the car can run forward again but only for few laps.

the fet doesn't burn and no burning smell too...
i try to resolder the fets and problem solved only for a while.
then i changed to stock fets but can't get rid of the problem.

Does anyone have this problem before?

thanks in advance.

Aurora
2007.08.28, 03:50 AM
Just out of curiosity, what motor are you using for this car? The original motor has a circuit breaker thing that will probably stop the car if there is too much current going thru. Also, do you experience any substantial heat problem with the motor?

ub0211042
2007.08.28, 03:57 AM
Just out of curiosity, what motor are you using for this car? The original motor has a circuit breaker thing that will probably stop the car if there is too much current going thru. Also, do you experience any substantial heat problem with the motor?

thanks for ur reply, im using old xspeed motor with out the circuit breaker
and the motor runs cool.

Aurora
2007.08.28, 04:28 AM
Are you using an AD band board? Some board members have reported AD band seems to have 'static' problem on RCP track:

http://www.mini-zracer.com/forums/showthread.php?t=24396

But not too sure whether this same problem might happen to stock boards or not..

ub0211042
2007.08.28, 02:00 PM
Are you using an AD band board? Some board members have reported AD band seems to have 'static' problem on RCP track:

http://www.mini-zracer.com/forums/showthread.php?t=24396

But not too sure whether this same problem might happen to stock boards or not..

i'm using a stock AM PCB, i'm having this problem after i change the FET's... :(

usually if the fets got damaged by static...what are the Symptoms?

Aurora
2007.08.28, 10:02 PM
Static damaged fets? I remembered other members with EE background might have contributed to this topic in the past, but I would think if the fets are indeed damaged by static, it will not work properly from the start.

The consistent pattern of 'working for a few laps, then fail', might indicate the problem is either related to heat or operation/mechanical problem. My guess are:

1) Motor, where after some run, the arm/case has expanded and rubbing each other to cause the stop. Though it is quite rare that it happens. If indeed is this problem, you will have a hard time pushing the car forward by hand after it stopped working.

2) Fet soldering. After some run, the fet might have heated some tiny bit, and if it wasn't solder on properly the first time, it might left itself off the pads when expanded. And after it is cooled, it gets connected again.

ub0211042
2007.08.28, 11:49 PM
Static damaged fets? I remembered other members with EE background might have contributed to this topic in the past, but I would think if the fets are indeed damaged by static, it will not work properly from the start.

The consistent pattern of 'working for a few laps, then fail', might indicate the problem is either related to heat or operation/mechanical problem. My guess are:

1) Motor, where after some run, the arm/case has expanded and rubbing each other to cause the stop. Though it is quite rare that it happens. If indeed is this problem, you will have a hard time pushing the car forward by hand after it stopped working.

2) Fet soldering. After some run, the fet might have heated some tiny bit, and if it wasn't solder on properly the first time, it might left itself off the pads when expanded. And after it is cooled, it gets connected again.

the number (2) seems like a valid reason.
one of my car had this problem before and after resoldering it, the problem is solved until now.

The other car with the same problem, i changed the fets to o brand new ones...seems like it is working fine. But need to keep my finger crossed coz the problem sometimes occoured after few days.