Help on this witchcraft :)

Rui's picture


Joined: May 26, 2019

Replies: 0
Help on this witchcraft :)
May 26, 2019 - 9:59pm

Hello everybody!


I was wondering if someone can help me with a problem that I’m dealing here.

Unfortunately some battery were forgotten (for long) inside of a Lavalier mic sender (Sennheiser sk100 g2) and the time allowed the acid to work/damage on some parts and I decided to clean as much as possible and even to replace a micro-switch (tough work).

Well... everything looked cool except for the fact that the device, after "cooling down", wouldn’t turn on again, showing only the bat sign and a random trace on the display, kind of crazy stuff and not a official warning.

After some "phisical reasearch" - blowing it with the air dryer to evaporate quicker the fat cleaner to take out he flux, it was working fine, after cooling down, same story again.

At the end I got to the conclusion that the part  that is broken/malfunction is this part on the imagem with the code SMI040M4. When I heat it up (leting the welder almost touching it) the device works 100%. When it cools down, again the malfunction.

(by the way, when I touch it with conductivity to the ground - with a metal part or finger -  it reboots the equipment, is it normal?)

Im a beginner in this world and I don’t even know what is this piece exactly? Another problem is that after googling it I didn’t find the latest clue about it . 

Any clues of what the hell Am I dealing here? Where can I get this piece and... is it easy to replace? Looking at the spot (and how I think is welded) I predict already a nightmare


All the the best and thank you for you help.




AISHA's picture


Joined: Sep 07, 2017

Replies: 248
Sounds like a soldering problem
May 28, 2019 - 8:06am

I think the chemicals which got leaked form the battery has damaged some of your solder pads breaking some connection. May be when you heat it up the connection is formed and then gradually as it cools it gets broken again. Without probing the PCB its hard to say which compoenet or conection has failed. However try these.


Clean your PCB with PCB cleaner (ISP) Isopropyl alcohol, if you cant find one you can use thinner that is normally used with paints. This cleaning will remove all the imputrites left behind by the battery chemical. then re-touch all the soldering spots to make sure they are in good shape. This should get it running i belive