General Power board question - Fuse, Rectifier, TVS

[llphat]

I had some issues recently with a few power boards with blown fuse, on checking it seems one of the bridge diode has shorted. After replacing the fuse and rectifier bridge, on power up the TVS (transient voltage suppressor) always explodes. Is this expected?

Or should the TVS also be changed once the bridge has a shorted diode?

The most recent case I had is the Dell 1800FP power board. Fuse F901 blown, on checking rectifier BD901 has a shorted diode after changing both TH902 explodes on power up.

[momaka]

Re: General Power board question - Fuse, Rectifier, TVS

Perhaps the high current that flows before the fuse blows is what damages those NTCs/TVSs.

Or should the TVS also be changed once the bridge has a shorted diode?

Not necessarily. But since it seems like a common occurance to you, maybe keep a few TVSs in stock just in case this happens.

Also, when the fuse and/or BR has blown, I suggest you use the incandescent light bulb series trick in series with the monitor to limit the current. That way, if there are more problems, the light bulb will light but will not blow your new fuse. Here's a thread on how to do it:
https://www.badcaps.net/forum/showpo...4&postcount=70

[R_J]

Re: General Power board question - Fuse, Rectifier, TVS

I suspect the tvs was also damaged by what ever surge took out the bridge. they don't always fail shorted, they can check open (or close to it) but when voltage is applied they blow