surface mount device codes

Posted on 2015-01-07
Last Modified: 2015-01-16
has any body got any idea what a surface mount device is with marking GFN 38 and also a diode symbol with its legs wrapped around to form a capital S. the device is 7mm long 5.5 mm wide and 2 mm deep, the two connections are on the short ends. it measures 4 ohms. It is in a dog perimeter minder circuit board , no bar marking on either end . just the symbol and text . the low value of ohms is causing over current draw on the 12 volt supply . i have extensive google search with  no success . removing the device from the board has solved the problem and it appears to work correctly . but mave not tried it with the dog collar.
Thanks for assistance in advance.
Question by:TopTed
  • 4
  • 3
LVL 27

Expert Comment

ID: 40537028
Presumably the circuit was working, then it stopped working, and you noticed the suspect part was getting hot.  I think what you have is a failed protection diode.  The circuit will work fine without it, but it will be at increased risk of damage from line voltage surges.
LVL 48

Expert Comment

ID: 40537126
I believe FN means Flat No-Lead.

However I can't get any further than that.
LVL 27

Accepted Solution

d-glitch earned 500 total points
ID: 40537875
A close-up photo of the circuit, suspect part, and logo could help a lot.  
There are dozens (if not hundreds) of possible manufacturers and many thousands of possible part numbers.

I believe the part is something like one of these:
Bipolar protection devices would not require an indicator band.
The suspect device probably wouldn't have measured 4 ohms when it was new and working.
Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.


Author Comment

ID: 40539947
LVL 27

Expert Comment

ID: 40539969
Thanks.  That isn't the official logo for ST, but they would probably be irked if another company used that mark.
I'll resume the search there.

Author Comment

ID: 40550609
If there is no further comment , i think i will put it back into service and hope there are no surges. thanks for looking , I have had no further success either.
LVL 27

Expert Comment

ID: 40551270
I have looked at the ST website and found more than a hundred of these parts with 3-letter codes, but none of them is a match for yours.  Some of the relevant data sheets are attached.  The 3-letter codes are on page 8.  The middle letter is always U or B (for unipolar and bipolar).  And the logo looks different too.

Author Closing Comment

ID: 40554859
I chose one of the vishay bidirectional devices as they were the same dimensins . i have put it in the pcb  and returned it to the customer and it is working ok. Thanks

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

A little history Back in 1997 when I built my first custom computer using the revolutionary Gateway website I didn’t have much to choose from except for the CPU. The race between computer manufacturers was held back by processor manufacturers. They…
Introduction: When a connection to the internet is established, there always exists a modem between the connected device and the ISP (Internet Service Provider). The Operating System (OS) on your PC controls the modem which communicates with the …
Two types of users will appreciate AOMEI Backupper Pro: 1 - Those with PCIe drives (and haven't found cloning software that works on them). 2 - Those who want a fast clone of their boot drive (no re-boots needed) and it can clone your drive wh…
The Email Laundry PDF encryption service allows companies to send confidential encrypted  emails to anybody. The PDF document can also contain attachments that are embedded in the encrypted PDF. The password is randomly generated by The Email Laundr…

828 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question