ESC repair, fried transistor- I need help from an expert!

[GoMachV]

Generally you need to put a bit of power to a diode to properly test it. I know on microwaves we need a good 9v battery to check for a working diode but ours are pretty big. Also keep in mind your testing within a circuit, without disconnecting one leg of each diode I don't see how you could get a clear reading

When connecting the signal wire alone you usually wouldn't get anything to the esc, you need the ground hooked up as well. Although you seem to have gone thru the paces, I wanted to clarify in case others tried

[85Edinger]

Also keep in mind your testing within a circuit, without disconnecting one leg of each diode I don't see how you could get a clear reading

When connecting the signal wire alone you usually wouldn't get anything to the esc, you need the ground hooked up as well. Although you seem to have gone thru the paces, I wanted to clarify in case others tried

It did occur to me that the current could be taking a different path through the circuit. Maybe I'll try de-soldering one end of each diode, then testing it.
So, how about that M5236L? Is it fried?
What do you mean about having ground hooked up? Do you mean the battery ground?
Lastly, if I turn out to have a few bad diodes, how do I find a replacement diode? There are no numbers or letters.
Thanks.

[GoMachV]

The connection between the esc and receiver, wether using the bec or not, needs the ground wire hooked up so the signal has a reference. Basically just pull the red wire

I'm not great at a component level, better leave that to the guys that know the small stuff

[85Edinger]

Okay, thanks. I'll try it again with the - wire in the plug.
Does anyone have any idea on the M5236L?

[jwscab]

If you can figure out which pin is pin 1 of the M5236L and it's connected to the burned out transistor, more than likely you have found your problem, and it's related to the BEC of the ESC. It may have been shorted out or overloaded causing the pass transistor to be overheated and damaged. you can't get voltage through the esc after the burned out transistor, so it's not getting powered.

this esc is peculiar in that most ecs have an integrated controller/pass transistor, such as something like a 78L05 type regulator. this one has a separate pass transistor and controller.

as far as diodes are concerned, you need to pass a tiny current through them in both directions to see if they work. most meters have a diode test port or selection on the switch, where it usually beeps. it will beep in one direction and if you flip the leads, it won't beep if the diode is working, but can be affected by other external circuitry.

as far as the FET's with only some connections, a FET can be used as a diode if you connect the right pins, and they may be used for motor shunts, like you would solder on externally with some ESC's.

EDIT: I took a closer look at some of the better pics of the bottom of the BEC. The manufacturers have some of the copper traces masked(the green epoxy), but the thin copper foil can only handle a certain amount of current. By unmasking the traces and folding over the FET leads, they can really beef up the high current paths through the FET's, that you NEED in order to keep copper losses to a minimum. the other signals are much lower current so the foil itself is plenty of copper to handle the signal load. So it's a 'cheap' way to increase the current capability of a trace. sorry for not looking closer the first time.

[85Edinger]

Thanks, very helpful.
Are you saying that if all the diodes test OK, I should just replace the M5236L and the 2SB1184?

[jwscab]

you may just need to change the 2sb1184. the controller probably isn't damaged, but to be absolutely sure, and if they are cheap enough, you could change both.

[85Edinger]

Okay, thanks.
I retested the esc with an rx batt, plugged into a 6s nimh, with only the red wire removed from the plug. No change- servo works, esc is lifeless.
I found 2SB1184 on Mouser.

[backlash]

dinger,

OK, good so your radio gear (transmitter, receiver and servos) are working OK..

Maybe I should have explained this first..

An ESC will typically get its power to operate from the 7.2V (6S) NiMh main battery via its inbuilt BEC.. That same BEC in the ESC is what usually powers the receiver and steering servo as well. When the BEC in the ESC has failed, you can often get it to work by replacing that power source with something else such as the standard 4 AA battery box, or an external BEC..

Because the BEC in your ESC is no longer providing power to run itself, it will need to get its power from the 4AA battery box via your receiver.. This means that you will need to have all 3 wires connected in the ESC's receiver plug.. The positive and negative wire (in the receiver plug) will transfer power from the receiver to the ESC.. The receiver will also send its signal to the ESC via the signal wire and the negative wire (I believe)..

When I asked you to connect the ESC's receiver plug to the receiver (without thee 7.2V NiMh battery connected) and turn the radio gear on and see if it operates, it was to see if the ESC could be powered by an external source, and if it still worked, without the risk of having 7.2V from the main battery come in contact with the 6 Volt "control" side of the receiver..

When you do this test, the steering servo should still work.. If the steering doesn't work with the ESC connected to the receiver, then something "could" be shorted in the ESC's BEC circuitry causing excessive load on the 4 AA batteries, and thus cause the voltage to drop to below the operating voltage of the receiver and servos.. You could test for this by placing your meter in DC volts test mode, and connecting the probes to the positive and negative output of the battery box (you should read approx. 6 Volts DC).. PLEASE UNDERSTAND that if the ESC is shorted internally, then the excess current created could overheat other components, and also the tracks in your receiver.. DO NOT leave it powered on for too long (at a guess, no longer than 10 seconds maximum) when doing these tests, shorter if possible..

What I had hoped was that the ESC would work off the 4AA battery box, and that would then enable you to use an External BEC instead, rather than bother replacing the faulty components in the ESC..

Does that make sense??

Look, I'm only an electrician, (Not an electronics tech) that has an informed, but limited knowledge of electronics..

As gomachv (Jeff?) has suggested, to correctly test most electronics components, you first need to remove then from the PCB (Printed Circuit Board) to avoid testing other components that may be in circuit with them as well. The problem is, that it is very easy to damage the components and the PCB tracks if too much heat is applied for too long by an inexperienced operator..

This is why I have suggested only basic tests (to start with)..

AND yes, when you are doing your tests of MOSFETS and diodes, your meter should be in diode test mode..

A good or working diode will conduct in one direction, but not the other.. (Test it with your meter leads one way, then swap your meter leads and test again).. A simple multimeter in diode test mode should be sufficient to measure most diodes.. I have used my Fluke meter to test 240 Amp Stud diodes with no troubles..

Zener diodes are different from regular diodes.. see here http://en.wikipedia.org/wiki/Zener_diode

Basic FET information.. http://en.wikipedia.org/wiki/FET When testing a FET you should be able to test for a diode between the source and drain, with your meter in diode test mode..

[85Edinger]

Okay, so I do a diode test between the outer two wires on the FETs?
Can that be accurately done with the FETs installed?
Last night I tested a few diodes with one end removed. They all tested OK. I got them all back in.
I'll try that test, sorry I misunderstood.
Is the M5236L supposed to conduct between the middle pin and one of the outer pins?

[jwscab]

Look at the data sheet for the M part. Its a controller. It gets feedback on one pin and controls how much the pass transistor 'flows' using pin one. Its a complicated circuit inside so don't worry about trying to test it separately. It needs to have all the pieces in the data sheet diagram in order to function. That's why I asked if the burnt out part is the transistor connected to pin one of the M part. The ESC is powered through that pass transistor.

[scr8p]

is this the only esc you have laying around? it just seems like an awful lot of trouble to go through for that. unless you're bored...... i guess.

if it's your only one, send me your address and you can have the traxxas xl-1 out of my kid's stampede.

[85Edinger]

No, this isn't the only ESC I have laying around. I have an Xl-5 in my Hawk 2, a GTB2 in my Rc10, a Hobbywing Sc8 in my Rustler, I even have an HPI Sc-15 in a broken toy grade.
I just think it might be nice to get this ESC working again. I just installed the Airtronics Sr-2p radio in my Hawk 2, and it would be cool to have a vintage ESC to go with it. I've learned a lot, too. It's just a project.
Your kid can keep his Stampede's Xl-1. Thanks, though.

[scr8p]

No problem. But if you change your mind let me know. It hasn't been in my kid's truck in a decade or so, he won't miss it.