Help identify this diode?

[mattpd]

I am very new to electronics repair. The project I am working on now is repairing a power board from a Panasonic LCD TV. While running tests on some of the components I notice one diode that read infinite resistance in both directions. This is a bad diode right? Or could it be my meter is not capable of measuring this particular diode?

If it is bad, could you help identify it? It has 2 legs, and is polarized. It is black with red lettering that reads "T3D 54." What can I use to replace it?

[budm]

Re: Help identify this diode?

Model number of the TV, Pictures of both side of the board and the location of this DIODE will help. You use the Diode function test, right?

[twbranch]

Re: Help identify this diode?

Make sure you are in the correct mode on the meter. If so its junk. As for what it is rated at for replacement?...not sure off hand.

[mattpd]

Re: Help identify this diode?

Its a Panasonic th42pd50u, and the location is D411. I just tracked down the service manual and on the schematics is says "ST03D-170" next to the component. It's Panasonic part number is B0BB17000010. Is this a normal diode or something special? I did have my meter on diode setting and both ways it reads 0L. If it is broken, what do I need to do to find an equivalent?

[budm]

Re: Help identify this diode?

It is a Snubber diode, usually used across the transformer or relay to suppress the back EMF. You can only look to see if it is shorted, but you cannot check and see if it has correct forward bias reading with you meter. It will show open circuit using you meter.
http://www.shindengen.co.jp/product_...4caedfa94aa482
You will need more than 170V to cause the Zener to go into conduction mode.

[mattpd]

Re: Help identify this diode?

Its not shorted, so I guess I can assume its still good for now? Out of curiosity, what other types of diodes would my meter not be able to test properly?

[budm]

Re: Help identify this diode?

More likely to be good, MOST of the time the Diode will fail shorted.
"types of diodes would my meter not be able to test "
Zener diode voltage, the meter will show the correct reading of the diode junction but it cannot show the Zener voltage point of the diode, only the forward voltage.
or really high voltage diode that are rated in the 2000V or higher, they will connected the diodes in series and encase it into one body.

[mattpd]

Re: Help identify this diode?

Thanks for your help!