Identify unknown component.

[Exo]

Hello,

I've been working on a broken PC power supply and i've found a strange component wich i've never seen before.
It looks like a regular diode, but i don't think it is. It's marked 'B1' while all the diodes on the rest of the board are marked 'D'.

It sits in series with the incoming AC and the bridge rectifier - so basically, all the current going to the power supply has to pass trough it. Every time i plug the power cord in this part lights up for a second asif arcing inside. I do measure 340Volts on the main capacitor - so i don't think this part is the problem but i would like to know what it is.

It's the red circled component on the top. Click the picture for a larger one.
**broken link removed**

Thanks.

 

[Nigel Goodwin]

Presumably some kind of spike suppressor?.

However, if you've got 340V on the cap, then that's not the fault anyway.

A very common cause is the startup resistor going O/C, this provides a temporary supply for the chip until the PSU starts running and feeds itself. When the resistor fails, the PSU won't start.

 

[Exo]

Presumably some kind of spike suppressor?.

After looking deeper into spike supressors, i've found this: Transient voltage suppression diode - Wikipedia, the free encyclopedia - Could it be that ? Altough it seems a TVS is supposed to go in parallel with the load, not in series.

I know it's not the problem part but it made me curious.

 

[ronv]

I think from where it is it is an inrush current limiter, but it does seem small for the job.