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Electronics => Repair => Topic started by: Samogon on March 03, 2018, 06:43:45 am

Title: [SOLVED] SOT23 351A3 markings cant identify
Post by: Samogon on March 03, 2018, 06:43:45 am

This is fluke 789 process meter failed to power on.
i have one good on the board. desoldered it and component tester said that it is mosfet n-ch with zenner between source and drain
i placed generic mosfet n-channel but without zenner and unit started working, but in off position it shows dashes, it mean not fully off, i suspect it is due to wrong transistor

Title: Re: SOT23 351A3 markings cant identify
Post by: Samogon on March 03, 2018, 12:32:56 pm

Looks like i have found it
NDS351AN On semiconductors
http://www.onsemi.com/PowerSolutions/product.do?id=NDS351AN (http://www.onsemi.com/PowerSolutions/product.do?id=NDS351AN)

Title: Re: SOT23 351A3 markings cant identify
Post by: Armadillo on March 03, 2018, 01:04:14 pm

Isn't that a typical bodily diode across drain and source. Where is the zener diode you are referring?
Will the dashes be the same in the off position?

Title: Re: SOT23 351A3 markings cant identify
Post by: Samogon on March 03, 2018, 01:10:24 pm

Dashes do appear at the off position
And maybe i was wrong about zenner, possible it was just diode.
I have already soldered it back and itnis under display with wierd snap-in system do not want to remove it. Who knows how much stress it can sustain.
Will order transistors on Monday, it is cheaper then fixing dosplay holder :)

Title: Re: SOT23 351A3 markings cant identify
Post by: Samogon on March 03, 2018, 04:11:58 pm

Correction:
Proper device found and it clearly states "Device marking 351A"
https://www.fairchildsemi.com/datasheets/ND/NDS351AN.pdf (https://www.fairchildsemi.com/datasheets/ND/NDS351AN.pdf)

Title: Re: [SOLVED] SOT23 351A3 markings cant identify
Post by: Samogon on March 10, 2018, 06:01:06 am

Installed transistor and dashes have disappeared when meter is off. That was simple repair.