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Diode Identify Please

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t_ian

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Hi
Can anyone identify a diode with the markings T3D 66. I can find no ref to it
anywhere or a equiv.

Ian
 

Could it be a transient suppressor i.e. no polarising markings?

Keith
 
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    t_ian

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keith1200rs said:
Could it be a transient suppressor i.e. no polarising markings?

Keith
Click to expand...

Keith

Board legend is D9, and it has a polarising strip. It is on the drain leg of a high voltage power mosfet switcher (TOP245YN). It measures o/c in both directions so reasonable to assume its dead, the switcher had a hole in it!!

Ian
 

Consult the TOP245 datasheet for a collection of suggested RCD and zener networks. The diode is most likely part of a similar circuit.
 

Hi,
Since it was on the drain of TOP245, it seems like it's a transzorb or an ultra fast recovery diode. Since you say there are no polarising markings, it could be a unipolar transzorb or an ultra fast recovery diode. One of the leads connects to the TOP245 drain, what is the other lead connected to? Possibly another diode or transzorb?

Tahmid.
 

Tahmid said:
Hi,
Since it was on the drain of TOP245, it seems like it's a transzorb or an ultra fast recovery diode. Since you say there are no polarising markings, it could be a unipolar transzorb or an ultra fast recovery diode. One of the leads connects to the TOP245 drain, what is the other lead connected to? Possibly another diode or transzorb?

Tahmid.
Click to expand...

Tahmid
Sorry I said it does have a polarising mark, the other end feeds into the isolation transformer.
Ian
 

I would follow FvM's suggestion. From the datasheet you should be able to work out a suitable replacement. It will probably depend on the design of the power supply (such as transistor breakdown voltage) but as you have the unit that should be ok.

Keith
 

Hi,
Sorry that was a typo. This is a transzorb if one end connects to TOP drain and the other to transformer(I'm assuming the high voltage positive line). You may be able to use a P6KE200 instead as this is most commonly used with TOP circuits.

Hope this helps.
Tahmid.
 

the other end feeds into the isolation transformer
Click to expand...
Doesn't seem to correspond to a standard TOP245 application circuit a first sight. The TOP245 drain pin is also supposed to feed into the transformer. Does it?

Personally, I would extract the primary side power circuit of the switcher with a continuity tester or a multimeter to understand the diode function.

An unipolar transzorb diode can't be connected to the transformer primary side without involving an additional rectifier diode. So I don't see clearly what Tahmid is suggesting.
 

Hi,
Sorry for the unclear explanation. The thing is usually what is done is either transzorb with diode or just transzorb if it's 2 back to back inside the package. I can't seem to find any diode named T3D. Maybe it's some transzorb with a diode inbuilt (diode not another transzorb, that's why the polar marking). So you could try with a diode and P6KE200(the unipolar one) or the back-to-back P6KE200(bipolar).

Hope I could make this clear.
Tahmid.
 
Last edited:

Thanks for everones help, will get data sheet and see what can be derived from that.

Ian
 

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