Identify damaged transistors.

[f114]

I have this card with two damaged transistors that can not be identified by numbering. Could anyone tell which transistors could replace them?

[Ian.M]

The lower one almost certainly isn't a transistor - it has 6 legs and the silkscreen says U2, so its probably an I.C.

Without knowing exactly what the board is, what it does, and maybe a fair bit of reverse engineering to find out how it works, you are S.O.L.

[technogeeky]

I would hazard a guess from both the size and package of the bottom chip that it's a transient voltage suppressor (TVS) array. It also looks like there's been some high voltage damage to the nearby traces, to the TVS itself, more traces, possibly the large-package SMD resistor (102).

If the remaining contacts of the supposed TVS chip read like... diodes in both directions, perhaps you could identify it as such. In any case, a TVS would make sense there.

Identifying the transistor will probably be more difficult, but you could start by assuming that it's the same transistor as another one of the same package size on the board (it looks like there is one with markings 16 on the board to the right).

Was this device in a situation where it could have been struck by lightning, or connected to something that was hit by lightning?

[f114]

The device has been damaged by lightening. The above damaged transistor only identifies an "A" in the encapsulation label.
Technogeeky thanks for the info.

[EPTech]

Hi There,

Can you get any markings of the IC? It may as well be a 1-gate logic IC or a dual transistor or FET, hard to tell. The resistor under R9 seems to be damaged as well and the trace running from that one to the IC looks like it has been vaporized.

Q5 may be a simple NPN transistor like a BC847. Check whether pin 2 in connected to GND after unsoldering Q5.

Happy repairing.

[Cyberdragon]

Everything in the circuit path of that IC has exploded, that little right angle trace below and to the IC (eww, bad layout), the trace to the resistor, the resistor itself, and the trace and via leading from the resistor. There could be more blown traces and components on the other side of that via, and hopefully it's only two layer.

[f114]

OK. thank you for the informations

[Ian.M]

The via between R9 and Q5 (by base of top arrow., bottom pic) looks suspicious.  Its on the track that had the short segment to U2 vaporised.   

My professional opinion is its FUBARed - even if you had original new replacements for  everything you can see that's visibly bad, and jumpered all the missing tracks and possibly damaged vias, you'll find further damage that will prevent it working properly and/or reliably.

e.g there's a track with a 330R series resistor from the blown transistor Q5 to pin 15 of the Holtek HT66F004 MCU so that's probably suffered as well and replacements for obscure custom programmed parts like that usually have to be salvaged off an identical donor board.