I've read a lot of threads here about TVS replacements and often people will suggest to use a TVS diode from any other board from the same voltage line. So I'm guessing 5v line TVS diodes are generally the same specs across all HDD.


So I went to my local electronics hobby shop to buy a replacement zener diode. [my 5V line diode fried, removed it, drive works, but I want protection to keep using the drive]

I was hit with a surprise question : What wattage?

This was written on the fried zener chip :
ST E
AE
637
[might have been a c in front of the 637, but the chip was cracked in the middle of the text]


So I'm assuming it was rated at ~6.3v

Anyway, I bought these two diodes:

6.2V 1watt 1N4735A
1N4735A: http://www.datasheetcatalog.org/datashe ... Xwuzrx.pdf



6.2V 5watt 1N5341B
1N5341B : http://www.datasheetcatalog.org/datashe ... 3b-88b.pdf


[both from STMicroelectronics]


They had other wattage and voltages, so I can go back if neither of those are adequate. [the diodes are dirt cheap anyway]

If that's relevant to knowing what's the "close enough" specs for a zener diode :
Seagate Barracuda 7200.10 320GB [ ST3320620A ]


I thank you in advance for any help.

Hi,

First of all, the TVS is an independent circuit from the other parts of the PCB.
During the normal use, the wattage is not important, because there is no current running through these.
But, when the spike comes, the better if the diode are as much strong as much can!

BTW, in 5V line, the 6.2-6.3V extremely high for protect the components from the "dead" limits, wich is 5.5V on almost all ICs.
This is why i am using lower (5.5-5.7V) protection trigger limits in my "HddGurad" units.....
A simple TVS protection is a minimal protection like the seatbelt.
But what about the airbags and similars?

Janos

thanks for the info! I'm going to go buy the 5.5v 5watt zener in that case.

However, was I right to assume that the original diode was 6.2~6.3v considering the markings?

Zener and Tvs are completely different things and completely differently working and are not meant as replacement zener for Tvs and viceversa. Anyway it's your problem.

When it comes to selecting a TVS the only criteria required is whether its 5v or 12v.
As in your case its 5v then just remove one from a scrap pcb and the job is done. No need to match part numbers etc as this is not a power component.
Its just a protection device so if the replacement is physically the same size then it will work as well as the original.

BlackSt and dick are right.

Zener is not the same as TVS.
You can't use Zener for the hdd protection!

Yes, usually 6.xV comes in the 5V line wich is sometimes enought, and sometimes not.
If you move closer to the 5.5V, the triggering will comes more often, but the protection gets stronger.
If you move more far, from the 5.5V, the triggerint will comes more rare, but the protection will good for nothing.

If you want the original protection, the best is, if you can remove the TVS from another hdd-pcb.

Janos

alright Ill go ask at the store if they have any TVS. When I asked for a TVS originally, the guy asked me "zener?" and since I read about zener here, somehow in threads where people talk about TVS, I assumed it was the same. [they look the same with the little stripe for the direction]

Go to another store.