X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com Message-ID: <5001303C.2060408@estechnical.co.uk> Date: Sat, 14 Jul 2012 09:39:24 +0100 From: Ed Simmons User-Agent: Mozilla/5.0 (X11; Linux i686; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 MIME-Version: 1.0 To: geda-user AT delorie DOT com Subject: Re: [geda-user] Help Identify MON Transistor?? References: <1342237267 DOT 98959 DOT YahooMailNeo AT web65902 DOT mail DOT ac4 DOT yahoo DOT com> In-Reply-To: <1342237267.98959.YahooMailNeo@web65902.mail.ac4.yahoo.com> Content-Type: multipart/alternative; boundary="------------050704030809040301000900" X-Authenticated-As: ed AT estechnical DOT co DOT uk Reply-To: geda-user AT delorie DOT com This is a multi-part message in MIME format. --------------050704030809040301000900 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 14/07/12 04:41, Edward Comer wrote: > This is a bit off-topic - but - I am reverse engineering a circuit > board so that I can make a new PCB with some changes. There are two > surface mounted transistors in SOT23 configuration. One that is marked > "t04" and using a multimeter, it tests out as an NPN transistor and I > found some documentation that states that a "t04" is a PMBS3904 which > is equivalent to a 2N3904. However, the markings of the second > transistor are a mystery to me (It is marked "MON") and it does not > test out as an NPN or PNP transistor. I suspect that it may be a > MOSFET. Does anyone have any info on this transistor??? If it is a mosfet the gate should appear to behave like a small capacitor (WRT one of the other pins). Do you have a capacitance meter? Package markings on small packages are sometimes completely unrelated to the ID of the part itself, ie batch/factory location/something else that's really not very helpful to you... My favourites are the parts with numbers sanded off... Does the circuit still work? If so you could probably get a good idea of the function of the part with a little careful observation of the circuit in operation. Alternatively, have you ever come across a transistor curve tester? These show excellent traces on a scope of the behaviour of the UUT. I was trying to find you a link to a really simple curve tester project, unfortunately I can't find it. Sorry... Many things about the PCB design around the part might give you clues as to it's type - some photos might mean we can help you better! HTH, Ed --------------050704030809040301000900 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
On 14/07/12 04:41, Edward Comer wrote:
This is a bit off-topic - but - I am reverse engineering a circuit board so that I can make a new PCB with some changes. There are two surface mounted transistors in SOT23 configuration. One that is marked "t04" and using a multimeter, it tests out as an NPN transistor and I found some documentation that states that a "t04" is a PMBS3904 which is equivalent to a 2N3904. However, the markings of the second transistor are a mystery to me (It is marked "MON") and it does not test out as an NPN or PNP transistor. I suspect that it may be a MOSFET. Does anyone have any info on this transistor???

If it is a mosfet the gate should appear to behave like a small capacitor (WRT one of the other pins). Do you have a capacitance meter?

Package markings on small packages are sometimes completely unrelated to the ID of the part itself, ie batch/factory location/something else that's really not very helpful to you... My favourites are the parts with numbers sanded off...

Does the circuit still work? If so you could probably get a good idea of the function of the part with a little careful observation of the circuit in operation. Alternatively, have you ever come across a transistor curve tester? These show excellent traces on a scope of the behaviour of the UUT. I was trying to find you a link to a really simple curve tester project, unfortunately I can't find it. Sorry...

Many things about the PCB design around the part might give you clues as to it's type - some photos might mean we can help you better!

HTH,
Ed
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