how to check these surface mount transistors and diodes?

[mattstolte]

I have this Panasonic sc board and they make a repair kit for this but I wanna know how to check these transistors and diodes?

[stj]

Re: how to check these surface mount transistors and diodes?

those are fet's
the good thing here is that fets usually fail by going short circuit.

meter between the pins - if there arent any shorted they are probably fine.

[tom66]

Re: how to check these surface mount transistors and diodes?

Like any other transistor, just check across pairs of pins for shorts.
The middle pin and tab are electrically connected internally, so you don't have to test that.

[CapLeaker]

Re: how to check these surface mount transistors and diodes?

if they are shorted, they are bad.

[tom66]

Re: how to check these surface mount transistors and diodes?

Yes, and if one transistor in a parallel "set" is bad, ALWAYS replace other transistors in that same set, as well as all transistors in series.
Failure to do this can lead to an explosive first power on...

[Ltank]

Re: how to check these surface mount transistors and diodes?

It takes a lot of heat to remove these mosfets. Chip-Quik can be very helpful. Care must be taken not to damage the foil traces on boards. Practice on a bad board that is not repairable

[tw2005]

Re: how to check these surface mount transistors and diodes?

check the IGBTs first in cct. then desolder and lift the 2 legs reconfirm whats shorted. You'll probably find with the shorted IGBTs isolated the diodes often will show as good.

check the gate resistors too once the bad IGBTs are removed.

[tom66]

Re: how to check these surface mount transistors and diodes?

It takes a lot of heat to remove these mosfets. Chip-Quik can be very helpful. Care must be taken not to damage the foil traces on boards. Practice on a bad board that is not repairable

I use 400C temperature with a 65W soldering iron. They come off easily. The pads are very large and hard to damage.

[tw2005]

Re: how to check these surface mount transistors and diodes?

I use 400C temperature with a 65W soldering iron. They come off easily. The pads are very large and hard to damage.

No dramas here either, likewise I use a quality broad tip to get that heat Transfer happening on the tabs, in fact I tin the whole tab.

[stj]

Re: how to check these surface mount transistors and diodes?

i heat the area from both sides with hot air, then put the iron on the tab with some solder.

[CapLeaker]

Re: how to check these surface mount transistors and diodes?

i heat the area from both sides with hot air, then put the iron on the tab with some solder.

x 2

[caphair]

Re: how to check these surface mount transistors and diodes?

I use hot air and flux. It slides off with slight pressure eventually.

[budm]

Re: how to check these surface mount transistors and diodes?

"how to check these surface mount transistors and diodes?" Same way as you test the Through hole devices. If it does not read right then you have to remove it and test it off the board.
Surface mounted device still functions the same way as the through hole device.

[mattstolte]

Re: how to check these surface mount transistors and diodes?

So just put in diode mode should read between 400 and 700 one way and open the opposite way?

[tom66]

Re: how to check these surface mount transistors and diodes?

Did you actually read any of the posts above?

[budm]

Re: how to check these surface mount transistors and diodes?

So just put in diode mode should read between 400 and 700 one way and open the opposite way?

That will only be true if there are no other components connected in parallel with the two legs of the device you are testing. If it shows conduction in both directions then you will need to remove it and test it again.
MOSFET is another story.
May be you should get a hold of some good NPN, PNP transistors and some N-CH, P-CH MOSFETS, then look up the pin out and take the readings to see what you get on the good device.