X-Authentication-Warning: delorie.com: mail set sender to geda-user-bounces using -f X-Recipient: geda-user AT delorie DOT com Message-ID: <50018FCF.7020203@estechnical.co.uk> Date: Sat, 14 Jul 2012 16:27:11 +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> <5001303C DOT 2060408 AT estechnical DOT co DOT uk> <1342277285 DOT 73961 DOT YahooMailNeo AT web65901 DOT mail DOT ac4 DOT yahoo DOT com> In-Reply-To: <1342277285.73961.YahooMailNeo@web65901.mail.ac4.yahoo.com> Content-Type: multipart/alternative; boundary="------------050301020107010108070900" 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. --------------050301020107010108070900 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit On 14/07/12 15:48, Edward Comer wrote: > 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? > - No, I have no capacitance meter. However, given that the E-B > junction has no conductivity in either direction, it would appear to > be MOSFET. Additionally, its function in the circuit is as a binary > switch of up to 500ma @ 5V. MOSFET would be good for such a purpose. > So given the E-B behavior and the intended function, I still suspect a > MOSFET. I was hoping that the "MON" would mean something meaningful > other than my assumption of "MO" - "N" channel. > > - I do have another circuit that I was working that has a > microcontroller with the markings removed.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. > - Yes, fully functional, which is the basis of my assumptions > mentioned above. I intend to clone the portion of the circuitry that > has the MON SOT-23 chip and I was just hoping that the "MON" would > actually identify the chip more precisely. > > - I don't think that the photo adds anything of value but it is at > this link: > http://www.flickr.com/photos/23036115 AT N03/7568124520/ > > - The link below has the portion of my reverse engineered schematic > that has the MON marked transistor, which is identified as Q2. It is > not, as far as I know, a BSS123 - that SYM was just handy. > http://www.flickr.com/photos/23036115 AT N03/7568162370/ > > - If no one knows exactly what it is, I intend to substitute a FDV303N > for it, in my cloned design: > http://www.fairchildsemi.com/pf/FD/FDV303N.html > If the substitute part can cope with your observations on the working board, there's not much to worry about unless very high speed switching is of interest. Best of luck! --------------050301020107010108070900 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit
On 14/07/12 15:48, Edward Comer wrote:
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?
- No, I have no capacitance meter. However, given that the E-B junction has no conductivity in either direction, it would appear to be MOSFET. Additionally, its function in the circuit is as a binary switch of up to 500ma @ 5V. MOSFET would be good for such a purpose. So given the E-B behavior and the intended function, I still suspect a MOSFET. I was hoping that the "MON" would mean something meaningful other than my assumption of "MO" - "N" channel.

- I do have another circuit that I was working that has a microcontroller with the markings removed.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. 
- Yes, fully functional, which is the basis of my assumptions mentioned above. I intend to clone the portion of the circuitry that has the MON SOT-23 chip and I was just hoping that the "MON" would actually identify the chip more precisely.

- I don't think that the photo adds anything of value but it is at this link:

- The link below has the portion of my reverse engineered schematic that has the MON marked transistor, which is identified as Q2. It is not, as far as I know, a BSS123 - that SYM was just handy.

- If no one knows exactly what it is, I intend to substitute a FDV303N for it, in my cloned design:


If the substitute part can cope with your observations on the working board, there's not much to worry about unless very high speed switching is of interest.

Best of luck!
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